Step 3 · 15–20% (with a system)

Nutrition

Assessment, therapeutic diets, feeding support, deficiencies and drug–food interactions.

Malnutrition, refeeding & nutrition support

Spot the patient who is not eating, feed through the gut whenever it works, and refeed a starved patient slowly with the electrolytes watched.

Rules to know

Inpatient eating little for days → screen for malnutrition by intake history, weight loss, muscle and fat loss, edema and grip strength, not by albumin
Near-zero intake for over 10 days or major recent weight loss → high refeeding risk; check phosphate, potassium and magnesium before feeding and replace as you go
Starting feeds in a refeeding-risk patient → thiamine before the first feed, begin near 10–20 kcal/kg/day, advance over several days, recheck electrolytes every 12–24 hours
New weakness, heart failure or breathing failure days into refeeding → hypophosphatemia from insulin-driven cell uptake; slow the feeds, give IV phosphate, put on a monitor
Cannot eat enough but the gut works → enteral feeding; parenteral nutrition only when the gut cannot be used or enteral feeds keep failing
Critically ill adult unable to eat, now hemodynamically stable → begin enteral feeds within 24–48 hours; hold them while pressor needs are climbing
Well-nourished ICU patient whose gut cannot be used → parenteral nutrition can usually wait about a week; start it early only if severely malnourished
Tube feeding expected for less than about 4 weeks → nasogastric or nasoenteric tube; longer need → gastrostomy
Blindly placed nasogastric feeding tube → confirm the tip on x-ray before any formula or medicine goes in
Vomiting or aspiration risk on gastric feeds → head of bed at 30–45°, a prokinetic, or move the tube tip past the pylorus
Gastric residual under 500 mL with no distension or vomiting → keep feeding; routine residual checks add little
Diarrhea on tube feeds → look for C difficile, sorbitol-containing liquid drugs, laxatives and antibiotics before blaming or stopping the formula
Fever in a patient receiving parenteral nutrition through a central line → line infection (staphylococci, Candida); paired cultures from line and periphery, consider pulling the catheter
Rising bilirubin and enzymes on months of parenteral nutrition → PN-associated liver disease; cycle the infusion, trim dextrose and lipid, restart enteral intake if possible
Hyperglycemia during parenteral nutrition → add insulin and trim dextrose; aim for glucose about 140–180 mg/dL in hospital
Inpatient energy and protein goals → about 25–30 kcal/kg/day; protein 1.2–2.0 g/kg/day if critically ill; avoid overfeeding in the first ICU days
Severely malnourished patient facing elective major surgery → 7–14 days of nutrition support beforehand, even if the operation is delayed
Healthy adult before elective anesthesia → clear liquids allowed until 2 hours before, a light meal until 6 hours; long overnight fasts are unnecessary
After abdominal surgery, including a fresh bowel anastomosis → offer oral intake within 24 hours as tolerated; waiting for flatus is outdated
Acute stroke on admission → bedside swallow screen before any food, drink or oral medicine; a failed screen → speech-language evaluation
Coughing or wet voice with liquids → videofluoroscopic swallow study or endoscopic swallow evaluation to choose food texture and liquid thickness
Food sticking in the chest seconds after swallowing, solids worse than liquids → esophageal dysphagia; upper endoscopy is the first test
Stroke patient who cannot swallow safely → nasogastric feeding within about a week; gastrostomy only if dysphagia lasts beyond 2–3 weeks
Mild acute pancreatitis → low-fat oral diet as soon as pain and nausea allow; severe disease with no oral intake → nasogastric or nasojejunal feeds, not parenteral
Child with edema, peeling skin, sparse pale hair and a fatty liver → kwashiorkor (protein lack); severe wasting with no edema → marasmus (total energy lack)
Child with severe acute malnutrition → correct hypoglycemia, hypothermia, dehydration and infection first, then start low-volume feeds before catch-up feeding

Traps that cost points

Labeling a septic patient malnourished because the albumin is 2.1→ Albumin and prealbumin fall with inflammation and fluid shifts. Diagnose malnutrition from intake, weight change, muscle and fat loss, and function.
Giving full calorie goals on day 1 to a patient who barely ate for 2 weeks→ Refeeding pushes phosphate, potassium and magnesium into cells. Start low with thiamine, check electrolytes often, then advance over days.
Choosing parenteral nutrition because the patient is very sick→ The indication is a gut that cannot be used, not illness severity. Enteral feeds protect the gut barrier and avoid central line infections.
Stopping tube feeds after one residual of 300 mL→ Residuals under 500 mL without vomiting or distension are not a reason to stop; repeated pauses are a common cause of underfeeding.
Letting a stroke patient take aspirin by mouth before the swallow screen→ Screen first; give aspirin rectally or by tube if the screen fails, so the first swallow is not an aspiration.
Keeping a postoperative patient NPO until bowel sounds return→ Early oral intake after surgery is safe, shortens ileus and length of stay; offer it within a day unless there is obstruction or vomiting.
Ordering parenteral nutrition for uncomplicated mild pancreatitis→ Most patients eat within days; early oral or enteral feeding lowers infection. Parenteral feeding is for the rare patient who cannot tolerate enteral feeds.

Vitamins & minerals: deficiencies, excess & who to supplement

In the Brain

Match the clue to the missing vitamin or mineral, confirm with the right level, treat, and know which healthy people actually need a supplement.

Rules to know

Confusion, ataxia, ophthalmoplegia in heavy drinking, hyperemesis or post-bariatric patient → Wernicke encephalopathy; high-dose IV thiamine at once, before or with glucose
High-output heart failure or symmetric neuropathy with poor diet or drinking → thiamine deficiency (wet or dry beriberi); IV thiamine
Macrocytic anemia with lost vibration and position sense → B12 deficiency; serum B12, plus methylmalonic acid when the level is borderline
Both methylmalonic acid and homocysteine high → B12 deficiency; homocysteine high with normal methylmalonic acid → folate deficiency
Low B12 with intrinsic factor antibodies → pernicious anemia; high-dose oral B12 works for most, injections first when neurologic deficits are severe
Macrocytic anemia, no neurologic signs, poor diet, drinking or methotrexate → folate deficiency; replace only after B12 is checked
Sun-exposed rash on neck and hands, diarrhea and confusion → pellagra (niacin lack) from heavy drinking, isoniazid or carcinoid; treat with nicotinamide
Bleeding gums, perifollicular hemorrhages, corkscrew hairs and poor wound healing → scurvy; vitamin C, and ask about a tea-and-toast or very narrow diet
Bone pain, proximal weakness, high alkaline phosphatase, low phosphate → osteomalacia; check 25-hydroxyvitamin D and replace D with adequate calcium
Bowed legs, wide wrists, rib beading in an unsupplemented breastfed child → nutritional rickets; vitamin D and calcium
Assessing vitamin D status → measure 25-hydroxyvitamin D, not 1,25-dihydroxyvitamin D; do not screen healthy adults without risk
Hypercalcemia with very high 25-hydroxyvitamin D and suppressed PTH → vitamin D toxicity from supplements; stop D and calcium, hydrate
Night blindness, dry eyes and Bitot spots after malabsorption or bariatric surgery → vitamin A deficiency; oral vitamin A
Any child with measles → vitamin A on two consecutive days; it lowers complications and death
Headache, papilledema, high liver enzymes on megadose vitamin A or retinoids → vitamin A toxicity; stop the source
Prolonged PT with long antibiotics, poor intake or cholestasis → vitamin K deficiency; the PT corrects after vitamin K
Every newborn → one IM vitamin K dose at birth; counsel parents who decline about late bleeding into the brain
Ataxia, lost proprioception and hemolysis with fat malabsorption (cystic fibrosis, cholestasis) → vitamin E deficiency
Sensory neuropathy in someone taking large daily B6 supplements → pyridoxine toxicity; stop the supplement
Scaly rash around mouth, anus and fingers with hair loss and diarrhea → zinc deficiency (IBD, alcohol, bariatric surgery, PN lacking trace elements); taste loss and poor healing too
Anemia, neutropenia and gait problems after bariatric surgery or heavy zinc use → copper deficiency; check copper and ceruloplasmin
Fatigue, ice craving and microcytosis → iron deficiency; a low ferritin confirms it, but inflammation can push ferritin into the normal range
Iron deficiency in a man or postmenopausal woman → upper endoscopy and colonoscopy plus celiac serology; never just replace iron
Oral iron causing nausea or constipation → every-other-day dosing absorbs better; IV iron for intolerance, malabsorption, ongoing loss or late pregnancy
Low potassium or calcium that will not correct → check and replace magnesium first
Cardiomyopathy or muscle pain after years of parenteral nutrition → selenium deficiency; check trace elements
Healthy adult taking vitamins to prevent heart disease or cancer → no proven benefit; beta-carotene raises lung cancer risk in smokers, vitamin E offers nothing
Strict vegan diet → lifelong B12 supplement; plan iodine, vitamin D, calcium and omega-3 sources too

Traps that cost points

Giving folic acid alone for macrocytic anemia before B12 is known→ Folate can correct the blood count while B12-related nerve and cord damage keeps progressing. Check B12 first and replace whichever is low.
Withholding dextrose from a hypoglycemic heavy drinker until thiamine arrives→ Give both together. Low glucose injures the brain within minutes; thiamine can go in the same minute, so neither waits.
Ordering 1,25-dihydroxyvitamin D to look for deficiency→ The active form is often normal or high in deficiency because PTH drives conversion. 25-hydroxyvitamin D reflects stores.
Treating iron deficiency in a 64-year-old man with pills and a recheck→ Unexplained iron deficiency in men and postmenopausal women is GI blood loss or malabsorption until shown otherwise; scope both ends and test for celiac.
Replacing potassium day after day without checking magnesium→ Low magnesium keeps the kidney wasting potassium and blocks PTH release; correct it and the potassium and calcium follow.
Suggesting beta-carotene to a smoker to protect the lungs→ Trials showed more lung cancer with beta-carotene in smokers. Advise quitting and a food-based diet instead of supplements.
Recommending months of high-dose zinc for wound healing or colds→ Excess zinc blocks copper absorption and can cause anemia, neutropenia and myeloneuropathy. Replace zinc only when deficient and for a limited time.

Obesity & weight management

In the Brain

Measure it, treat it as a chronic disease with lifestyle plus drugs or surgery when criteria are met, and prevent the deficiencies and pitfalls that follow.

Rules to know

Adult BMI → 25–29.9 overweight, 30 or more obesity, 40 or more severe; use lower cut points (23 and 27.5) in Asian patients
Waist over 40 inches in men or 35 inches in women → central fat with higher cardiometabolic risk even when the BMI looks modest
Adult with obesity → refer to an intensive multicomponent behavioral program (diet, activity, self-monitoring) with many contacts over the first year
Weight-loss lifestyle prescription → daily deficit near 500–750 kcal, 150 or more minutes weekly of activity, closer to 200–300 minutes to keep weight off
Loss of 5–10% of body weight → better BP, glucose, triglycerides, sleep apnea, fatty liver and knee pain; set this as the first goal
New patient with obesity → check BP, A1c or fasting glucose, lipids, liver enzymes and sleep apnea symptoms; test thyroid or cortisol only with suggestive features
Weight gain after starting olanzapine, insulin, a sulfonylurea, steroids, mirtazapine or valproate → switch to a weight-neutral option when one exists
BMI 30 or more, or 27 or more with a weight-related condition → add anti-obesity medication to lifestyle treatment
Choosing an anti-obesity drug → weekly semaglutide or tirzepatide give the largest loss; titrate slowly to limit nausea and vomiting
Obesity with established cardiovascular disease, no diabetes → semaglutide lowers major cardiovascular events; favor it
Obesity with moderate to severe obstructive sleep apnea → tirzepatide carries an approved sleep apnea indication
Personal or family history of medullary thyroid cancer or MEN2 → avoid GLP-1 receptor agonists and tirzepatide
Severe abdominal pain on a GLP-1 based drug → think pancreatitis or gallbladder disease; hold the drug and evaluate
Tirzepatide with an oral contraceptive → add a barrier method or switch to a non-oral method for 4 weeks after starting and after each dose increase
Planning pregnancy on semaglutide → stop it at least 2 months before trying to conceive; anti-obesity drugs are not used in pregnancy
Phentermine-topiramate → teratogenic, so pregnancy test before and during use with reliable contraception; avoid with glaucoma, hyperthyroidism or MAO inhibitors
Naltrexone-bupropion → avoid with seizure disorder, bulimia or anorexia, chronic opioid use or uncontrolled hypertension
Orlistat → oily stools and fat-soluble vitamin loss; daily multivitamin taken at bedtime, apart from the drug
Under 5% weight loss after 12 weeks on the full dose → stop that drug and change the plan
Stopping a GLP-1 based drug → most lost weight returns; plan long-term treatment as for any chronic disease
BMI ≥35, or 30–34.9 with type 2 diabetes or metabolic disease → offer metabolic and bariatric surgery referral
Child or teen with BMI at or above the 95th percentile → intensive family-based behavioral treatment; drugs from age 12, surgery referral from 13 when severe
After gastric bypass or sleeve → lifelong multivitamin, calcium citrate, vitamin D and B12, plus iron if menstruating; check labs at least yearly
Cramps, diarrhea, flushing, palpitations soon after sweets post-bypass → early dumping (within 30 minutes); small meals, no simple sugars, liquids apart from solids
Sweating and confusion 1–3 hours after eating, months after bypass → late dumping with reactive hypoglycemia; low-glycemic meals with protein, acarbose if needed
After bariatric surgery → delay pregnancy 12–18 months, use non-oral contraception after bypass, and avoid NSAIDs because of marginal ulcers
Rapid weight loss after bariatric surgery → ursodiol for about 6 months lowers gallstone formation
Drinking after gastric bypass or sleeve → faster, higher blood alcohol and more alcohol use disorder; counsel and screen at follow-up

Traps that cost points

Advising a patient to eat less and move more, then ending the visit→ Refer to a structured, intensive program and schedule follow-up; brief advice alone rarely produces lasting loss.
Starting semaglutide in a patient whose father had medullary thyroid cancer→ Personal or family history of medullary thyroid cancer or MEN2 contraindicates GLP-1 based drugs; choose another agent or surgery.
Prescribing phentermine-topiramate without discussing pregnancy→ Topiramate causes oral clefts. Confirm a negative pregnancy test and reliable contraception before starting and during treatment.
Continuing an anti-obesity drug that produced 2% loss at 4 months→ Lack of 5% loss after 12 weeks at full dose predicts poor long-term response; stop it and try another drug or approach.
Ordering a large endocrine panel for every patient with obesity→ Secondary causes are uncommon; test thyroid or cortisol only when the history or exam points to them.
Prescribing ibuprofen for knee pain after gastric bypass→ NSAIDs cause marginal ulcers and perforation after bypass; use acetaminophen, topical agents or other non-NSAID options.
Recommending calcium carbonate after gastric bypass→ Carbonate needs stomach acid; calcium citrate is absorbed better after bypass and with acid suppression.
Relying on the pill alone for contraception after gastric bypass→ Oral absorption is unreliable after bypass; offer an IUD, implant or other non-oral method and delay pregnancy 12–18 months.

Diets for heart, blood pressure, diabetes, lipids, gout & stones

In the Brain

Prescribe the eating pattern that fits the disease, give the specific numbers that matter, and know when diet alone is not enough.

Rules to know

Elevated BP or hypertension → DASH pattern (fruits, vegetables, low-fat dairy, whole grains, less saturated fat); drops systolic BP about 11 mm Hg in hypertension
Sodium advice in hypertension → under 2300 mg a day, ideally near 1500; cutting even 1000 mg a day helps
Hypertension with normal kidney function and no potassium-sparing drugs → raise dietary potassium; a potassium-enriched salt substitute is reasonable
CKD or on an ACE inhibitor, ARB or spironolactone → avoid potassium salt substitutes and supplements without a level check
Lifestyle steps that lower BP → weight loss (about 1 mm Hg per kg lost), DASH, less sodium, more potassium, regular exercise, less alcohol
High cardiovascular risk asking which diet → Mediterranean pattern with olive oil, nuts, fish, legumes and vegetables; it lowers cardiovascular events
High LDL → swap saturated fat for unsaturated fat (saturated near 6% of calories), avoid trans fat, add soluble fiber and plant sterols
High-risk patient eligible for a statin → start it now with diet; do not make months of diet a prerequisite
Triglycerides 500 mg/dL or more → no alcohol, little refined sugar, very low fat diet if 1000 or more, control glucose; fibrate to prevent pancreatitis
Triglycerides 150–499 → weight loss, fewer added sugars and refined starches, less alcohol, and fix secondary causes such as diabetes or hypothyroidism
New diabetes → registered dietitian and self-management education at diagnosis, yearly, and when complications or life changes arise
Diabetes meal plan → no single ideal carbohydrate share; favor nonstarchy vegetables and whole foods, fewer refined carbohydrates and no sugary drinks
Type 1 diabetes or multiple daily insulin injections → carbohydrate counting with an insulin-to-carbohydrate ratio
Fixed insulin doses or a sulfonylurea → similar carbohydrate amounts at regular meal times to prevent hypoglycemia
Glucose under 70 mg/dL in an awake patient → 15–20 g of fast glucose, recheck in 15 minutes, then a snack or meal
Hypoglycemia on acarbose → glucose (dextrose) tablets; table sugar is absorbed too slowly
Alcohol with insulin or a sulfonylurea → delayed hypoglycemia, often overnight; drink only with food and check glucose at bedtime
Recent type 2 diabetes with overweight → large weight loss (around 10–15 kg) can bring remission; offer a structured program
Prediabetes → intensive lifestyle program aiming for 7% weight loss and 150 minutes of weekly activity; metformin if BMI 35 or more, under 60, or prior gestational diabetes
Screening alcohol use → at-risk drinking is more than 4 drinks a day or 14 a week for men, more than 3 a day or 7 a week for women
Patient asking about safe drinking → less is better; even light drinking raises cancer risk, so never advise starting alcohol for the heart
Gout → weight loss, fewer organ meats, shellfish, beer, liquor and fructose-sweetened drinks; diet alone rarely reaches urate target
Recurrent kidney stones → enough fluid to pass at least 2.5 L of urine daily, with less sodium and animal protein
Calcium oxalate stones → keep normal dietary calcium (1000–1200 mg); low-calcium diets raise oxalate absorption and stones
Uric acid stones → more fluid, less animal protein, potassium citrate to alkalinize urine
Heart failure diet → avoid excess sodium; restrict fluid only for hyponatremia or stubborn congestion; weigh daily and report quick gains
Over-the-counter fish oil for prevention → no proven benefit; prescription icosapent ethyl only for high triglycerides with ASCVD or diabetes on a statin

Traps that cost points

Telling a calcium oxalate stone former to cut out dairy→ Dietary calcium binds oxalate in the gut; restricting it raises urinary oxalate and stone risk. Keep normal calcium, cut sodium, drink more.
Treating low glucose with chocolate or peanut butter→ Fat slows absorption and delays recovery. Use 15–20 g of fast glucose, recheck in 15 minutes, then eat.
Delaying a statin in a high-risk patient for a 6-month diet trial→ Diet helps but rarely closes a large LDL gap; start the statin by risk and continue diet counseling.
Recommending a potassium salt substitute to a patient with CKD on lisinopril→ Potassium chloride substitutes plus reduced excretion can cause dangerous hyperkalemia; advise herbs and spices instead.
Suggesting a glass of red wine daily for heart health→ No trial supports starting alcohol for cardiovascular benefit, and cancer risk rises with any intake.
Promising a gout patient that diet will replace allopurinol→ Diet lowers urate only modestly; patients with tophi, frequent flares or urate stones need urate-lowering drugs too.
Fluid-restricting every patient with heart failure→ Fluid limits help mainly in hyponatremia or refractory congestion; for most, sodium moderation and diuretic adjustment matter more.
Giving every diabetic patient the same fixed macronutrient split→ Several patterns work; individualize to preferences, drugs and goals, and match carbohydrate to insulin when doses are fixed.

Diets for kidney, liver & gut disease

In the Brain

Adjust protein, salt, potassium and phosphate to the kidney, never starve the cirrhotic liver of protein, and match the diet to the gut that is left.

Rules to know

CKD stages 3–5 not on dialysis → protein near 0.8 g/kg/day, no high-protein diets (over 1.3 g/kg), dietitian referral
CKD with hypertension or edema → sodium under 2 g a day
CKD with hyperkalemia → cut high-potassium foods and salt substitutes, review drug doses, consider a potassium binder before stopping kidney-protective drugs
CKD with high phosphate → limit processed foods and colas with phosphate additives; give a phosphate binder with meals
Hemodialysis → protein raised to about 1.0–1.2 g/kg/day, limits on fluid, potassium, phosphate and sodium, plus a renal B-complex and C vitamin
Big weight gain between dialysis sessions → too much salt and fluid; counsel sodium and fluid limits
Advanced CKD → avoid magnesium or aluminum antacids and laxatives and phosphate enemas
Peritoneal dialysis → dialysate glucose adds calories and raises glucose, and protein is lost into the fluid; keep protein intake generous
Nephrotic syndrome → normal protein (not high), low sodium and lipid treatment; extra protein worsens proteinuria
Cirrhosis → protein 1.2–1.5 g/kg/day, meals every few hours and a late-evening carbohydrate snack; avoid long fasts
Hepatic encephalopathy → keep normal protein intake; treat with lactulose, add rifaximin for recurrence
Cirrhosis with ascites → sodium about 2 g a day; restrict fluid only when serum sodium falls below about 125 mEq/L
Fatty liver disease with overweight → lose 7–10% of weight (10% or more for fibrosis), Mediterranean diet, no sugary drinks, little or no alcohol
Hemochromatosis → no iron or vitamin C supplements and no raw shellfish; phlebotomy, not diet, removes the iron
Wilson disease → limit copper-rich foods (shellfish, organ meats, nuts, chocolate, mushrooms) alongside chelation or zinc
Suspected celiac → tTG-IgA with total IgA while still eating gluten; if already gluten-free, a gluten challenge or HLA-DQ2/DQ8 testing first
Confirmed celiac → lifelong strict gluten-free diet (no wheat, barley or rye; uncontaminated oats are fine), dietitian, check iron, folate, B12 and vitamin D
Celiac with ongoing symptoms despite the diet → hidden gluten is the usual cause; dietitian review and repeat tTG before more testing
Chronic pancreatitis with fatty stools or weight loss → fecal elastase; if low, pancreatic enzymes with every meal and snack, adding acid suppression if response is poor
Pancreatic exocrine insufficiency → do not restrict fat; check fat-soluble vitamins and bone density
Short bowel with an end jejunostomy → oral rehydration solution; plain water, juice and sugary drinks increase stoma output
Short bowel with colon still attached → complex carbohydrates, lower fat, low oxalate to prevent stones, calcium with meals
Terminal ileum resected → B12 injections once over about 60 cm is lost; bile-acid diarrhea after resections under 100 cm responds to cholestyramine, longer losses cause fatty stools
Crohn disease with strictures → low-residue diet; child with active Crohn disease → exclusive enteral nutrition can induce remission
Bloating and diarrhea after dairy → lactose intolerance; reduce rather than eliminate lactose, use lactase, yogurt and hard cheese, keep calcium up
IBS with bloating → soluble fiber such as psyllium and a time-limited low-FODMAP trial with a dietitian, then reintroduction; avoid bran
Diverticulosis → high-fiber diet; nuts, seeds and popcorn are allowed
Gastroparesis → small frequent low-fat, low-fiber meals, liquids or purees later in the day, tight glucose control
GERD → weight loss, last meal 2–3 hours before bed, raised head of bed; avoid foods only when they clearly trigger symptoms

Traps that cost points

Restricting protein in a cirrhotic patient with encephalopathy→ Protein restriction worsens muscle loss and survival. Keep 1.2–1.5 g/kg/day and treat encephalopathy with lactulose and rifaximin.
Prescribing a high-protein diet to replace urinary losses in nephrotic syndrome→ Extra protein raises proteinuria without raising albumin; aim for normal intake with sodium restriction.
Advising a gluten-free diet before celiac serology is sent→ Serology and biopsy normalize off gluten, leaving the diagnosis uncertain for life. Test first while the patient is still eating gluten.
Treating pancreatic steatorrhea with a very low fat diet→ Fat restriction worsens weight loss and vitamin deficits. Replace enzymes with meals and adjust the dose to symptoms and weight.
Telling a patient with a high-output jejunostomy to drink more water→ Hypotonic fluid pulls sodium into the gut and raises output. Use an oral rehydration solution and limit plain water.
Cutting sodium below 1 g a day for ascites→ Very strict limits make food unpalatable and worsen malnutrition; about 2 g a day plus diuretics is the target.
Stopping an ACE inhibitor in CKD for a potassium of 5.4→ First review diet, salt substitutes and other drugs, and consider a binder, so the kidney-protective drug can continue.
Using a magnesium citrate bowel prep in advanced CKD→ Magnesium and phosphate preparations can cause toxicity or acute phosphate nephropathy; choose a polyethylene glycol prep.

Pregnancy, breastfeeding, infant & child nutrition

In the Brain

Supplement before conception, guide weight gain and food safety in pregnancy, protect breastfeeding, and time vitamin D, iron, solids, peanut and milk correctly.

Rules to know

Anyone who could become pregnant → folic acid 0.4–0.8 mg daily from at least 1 month before conception
Previous pregnancy with a neural tube defect → folic acid 4 mg daily from before conception through the first trimester
Prenatal vitamin → should contain iodine 150 mcg, iron and folic acid; avoid high-dose preformed vitamin A
Pregnancy weight gain by starting BMI → underweight 28–40 lb, normal 25–35, overweight 15–25, obesity 11–20
Extra calories in pregnancy → none in the first trimester, about 340 a day in the second, 450 a day in the third; no weight-loss diets
Fish in pregnancy and lactation → 2–3 servings a week of low-mercury fish; avoid shark, swordfish, king mackerel, tilefish, bigeye tuna and marlin
Listeria prevention in pregnancy → no unpasteurized milk or soft cheese, deli meats or smoked seafood unless heated until steaming, no raw sprouts
Toxoplasma prevention in pregnancy → cook meat fully, wash produce, wear gloves to garden, let someone else change cat litter
Caffeine and alcohol in pregnancy → caffeine under 200 mg a day; no amount of alcohol is known to be safe
Hyperemesis needing IV fluids → thiamine before dextrose, check electrolytes; pyridoxine with doxylamine for nausea
Gestational diabetes → medical nutrition therapy with glucose self-monitoring first; insulin if targets are not met
Vegan pregnancy → plan B12, iron, iodine, vitamin D, choline and DHA; an unsupplemented vegan mother's breastfed infant can become B12 deficient
Pregnancy after bariatric surgery → check iron, B12, folate and vitamin D; screen for gestational diabetes with glucose monitoring, not a sugar drink
Low-income pregnant, postpartum or breastfeeding woman, or child under 5 → refer to WIC for food, formula support and nutrition counseling
Infant feeding plan → exclusive breastfeeding for about 6 months, continuing with solids to 1 year or longer
Breastfeeding contraindicated → classic galactosemia in the infant, maternal HTLV, untreated brucellosis, illicit drug use, or radioactive or cytotoxic therapy
Mother with HIV in the US → formula or donor milk removes transmission risk; if virally suppressed on ART and she wants to breastfeed, support it with close follow-up
Not reasons to stop breastfeeding → hepatitis B or C, mastitis, a cold, most antidepressants, or stable methadone or buprenorphine treatment
Untreated active TB → separate until treated about 2 weeks but give expressed milk; herpes lesion on one breast → nurse from the other side
Breastfed or partly breastfed infant → vitamin D 400 IU daily from the first days until drinking about 1 liter of formula or milk daily
Term breastfed infant → oral iron 1 mg/kg/day from 4 months until iron-rich foods are eaten; preterm infants start earlier at a higher dose
Starting solids → around 6 months and not before 4, iron-rich foods early, no honey before age 1 (botulism)
Infant with severe eczema or egg allergy → peanut-containing food at 4–6 months; allergy testing first may be considered but should not delay it
Cow's milk → not the main drink before 12 months; after 1 year keep to about 16–24 oz a day, since more causes iron deficiency
Fruit juice → none before age 1, small daily limits after, never in a bottle at bedtime
Formula mixed with extra water → hyponatremia and seizures; too little water → hypernatremia; mix exactly as labeled
Newborn down over 10%, or below birth weight at 2 weeks → assess latch and feeding frequency, lactation support, recheck weight in days
Infant weight crossing two major percentile lines, length and head spared → inadequate intake is most likely; detailed diet history and observed feeding
Failure to thrive → few labs, guided by history; admit for severe malnutrition, failed outpatient care or concern for neglect

Traps that cost points

Telling a mother with mastitis to stop nursing on that side→ Continued emptying speeds recovery and prevents abscess; keep breastfeeding or pumping and treat with an antistaphylococcal antibiotic if needed.
Putting a pregnant woman with obesity on a weight-loss diet→ Aim for 11–20 lb of gain with healthy eating and activity; deliberate weight loss in pregnancy is not advised.
Advising parents to delay peanut until age 3 in an infant with eczema→ Early introduction at 4–6 months lowers peanut allergy; delay raises it.
Switching a 9-month-old to whole cow's milk→ Before 12 months cow's milk causes iron deficiency and occult GI blood loss; continue breast milk or formula.
Telling a pregnant patient to avoid all fish→ Low-mercury fish supply DHA for fetal brain development; recommend 2–3 servings a week and list the high-mercury fish to avoid.
Ordering a broad lab panel and endocrine tests first for failure to thrive→ Most cases are inadequate intake; a careful diet history, observed feeding and growth tracking find the cause more often than labs.
Telling a mother with hepatitis C she cannot breastfeed→ Hepatitis C is not spread by breast milk; pause only if nipples are cracked and bleeding.
Adding rice cereal to a 2-month-old's bottle to help sleep→ Solids before 4 months add choking and overfeeding risk without improving sleep; start solids around 6 months by spoon.

Weight loss, aging, serious illness, alcohol & eating disorders

In the Brain

Work up unintentional weight loss systematically, protect muscle in older adults, feed for comfort near life's end, and recognize the medical danger signs of eating disorders.

Rules to know

Older adult losing over 5% of weight in 6–12 months → review intake, mood, teeth, swallowing, drugs, money, cognition; CBC, CMP, TSH, CRP, urinalysis, chest film, due cancer screening
Unexplained weight loss with a normal first workup → watchful follow-up in 1–6 months rather than whole-body imaging
Weight loss after starting donepezil or another cholinesterase inhibitor → anorexia is a known effect; lower the dose or stop
Drug causes of poor appetite in older adults → digoxin toxicity, metformin, SSRIs early on, opioid constipation, anticholinergic dry mouth; review the list
Older adult with depression, poor appetite and insomnia → mirtazapine is a sensible antidepressant choice
Megestrol for appetite in an older adult → avoid; small fat gain with more clots, adrenal suppression and deaths
Isolated older adult eating little because of cost or mobility → two-question food insecurity screen, then home-delivered meals, SNAP and community programs
Protein for older adults → about 1.0–1.2 g/kg/day; resistance exercise plus protein best protects muscle (sarcopenia)
Community-dwelling older adult without vitamin D deficiency → vitamin D does not prevent falls; prescribe strength and balance exercise
Advanced dementia with eating problems → careful hand feeding; feeding tubes do not prolong life, prevent aspiration or heal pressure injuries
Pressure injury in a malnourished patient → about 30–35 kcal/kg and 1.25–1.5 g/kg protein daily; zinc or vitamin C only if deficient
Cancer with poor intake → dietitian, small energy-dense meals and oral supplements; tube or IV feeding only for gut failure with a reasonable prognosis
Advanced cancer with appetite loss → short-term dexamethasone, a progestin or low-dose olanzapine can help appetite; weigh side effects
Neutropenic patient asking about diet → safe food handling; a restrictive neutropenic diet shows no benefit
Actively dying patient no longer eating → hunger and thirst are rarely distressing; offer mouth care; artificial nutrition is a treatment that may be declined
Heavy drinker admitted for any reason → thiamine (IV if Wernicke risk), folate and a multivitamin; check magnesium and phosphate
Alcoholic ketoacidosis → dextrose-containing saline plus thiamine; insulin is not needed
Low weight with bradycardia, hypothermia, amenorrhea and lanugo → anorexia nervosa; ECG, electrolytes with phosphate and magnesium, glucose
Eating disorder with unstable vitals or labs → admit for HR under 50, BP under 90/45, temperature under 35.6 °C, arrhythmia, electrolyte derangement or food refusal
Inpatient refeeding in anorexia → start nutrition promptly with daily phosphate, potassium and magnesium checks and cardiac monitoring in the first week
Anorexia with low bone density → weight restoration and return of menses; oral contraceptives do not rebuild bone
Parotid swelling, eroded teeth, knuckle calluses and hypokalemic metabolic alkalosis → bulimia nervosa; CBT plus fluoxetine
Eating disorder needing an antidepressant → avoid bupropion because of seizure risk
Recurrent binges without compensatory purging → binge-eating disorder; CBT, with lisdexamfetamine if medication is needed
Young athlete with missed periods, stress fracture and low intake → low energy availability (female athlete triad); raise intake before anything else

Traps that cost points

Prescribing megestrol for weight loss in a nursing home resident→ Gains are small and mostly fat while clots, adrenal suppression and mortality rise. Address intake, mood, teeth, drugs and food access instead.
Ordering a whole-body CT before basic history, exam and labs for weight loss→ Most causes surface with history, exam and simple tests; imaging without a lead adds incidental findings, not answers.
Placing a gastrostomy tube in advanced dementia because the patient eats little→ Tube feeding does not extend life or prevent aspiration here; careful hand feeding aligned with goals of care is preferred.
Starting an oral contraceptive to protect bone in anorexia nervosa→ Withdrawal bleeds hide amenorrhea without restoring bone; weight restoration is the treatment.
Choosing bupropion for depression in a patient with bulimia→ Purging and electrolyte shifts raise seizure risk with bupropion; use an SSRI such as fluoxetine.
Giving insulin for alcoholic ketoacidosis→ Glucose is normal or low; dextrose and saline shut off ketogenesis. Give thiamine and replace potassium, magnesium and phosphate.
Ordering a neutropenic diet for a patient on chemotherapy→ It adds restriction without lowering infection; teach safe food handling and cooking instead.
Starting IV fluids and tube feeds in a dying patient because family fears starvation→ Explain that loss of appetite is part of dying and artificial nutrition rarely adds comfort; offer mouth care and honor stated wishes.

Drug–nutrient & supplement interactions

In the Brain

Know which foods and supplements change drug levels or effects, which drugs drain vitamins and minerals, and always ask what the patient buys over the counter.

Rules to know

Patient on warfarin → keep vitamin K intake steady rather than avoiding greens; a sudden rise in leafy greens lowers the INR
INR swings when tube feeds start or stop on warfarin → formula vitamin K and binding change the effect; check INR closely
Patient on a DOAC asking about greens → no vitamin K limits; take rivaroxaban 15 or 20 mg with the evening meal
Warfarin with fish oil, ginkgo, garlic or high-dose vitamin E → added bleeding risk; ask about every supplement
MAO inhibitor → avoid tyramine-rich aged cheese, cured or fermented meats, tap beer and soy sauce; risk is hypertensive crisis
Severe headache and high BP after aged cheese on an MAO inhibitor → tyramine crisis; IV phentolamine
Daily grapefruit juice → raises simvastatin, lovastatin, felodipine, cyclosporine, tacrolimus and amiodarone; use pravastatin or rosuvastatin, or stop grapefruit
St John's wort → induces CYP3A4 and P-gp: contraceptive failure, transplant rejection, low INR, HIV drug failure; serotonin syndrome with SSRIs
Isoniazid → add pyridoxine for pregnant, diabetic, HIV, alcohol-using, malnourished or CKD patients to prevent neuropathy
Long-term metformin → check B12 periodically, especially with neuropathy or anemia
Long-term PPI → watch for B12 deficiency, low magnesium (check if also on diuretics or digoxin), poorer iron and calcium carbonate absorption
Levothyroxine → empty stomach 30–60 minutes before breakfast, 4 hours apart from calcium, iron and bile-acid binders
TSH rising after starting iron or calcium → absorption interference; separate the doses before raising levothyroxine
Odd thyroid results or falsely low troponin in a high-dose biotin user → assay interference; stop biotin a few days and repeat
Tetracyclines or fluoroquinolones → take 2 hours before or several hours after dairy, antacids, calcium, iron, zinc or magnesium
Oral bisphosphonate → take on waking with plain water, nothing else for 30 minutes, stay upright
Lithium → low-salt diets, dehydration, thiazides, NSAIDs and ACE inhibitors raise levels; keep salt and fluid intake steady
ACE inhibitor, ARB, spironolactone or trimethoprim → caution with potassium supplements and potassium salt substitutes
Methotrexate → folic acid daily or weekly lowers mouth sores and liver toxicity; avoid trimethoprim-sulfamethoxazole
Phenytoin through a feeding tube → continuous feeds lower absorption; pause feeds around doses and follow levels
Long-term enzyme-inducing antiseizure drugs → vitamin D deficiency and bone loss; supplement and assess bone health
Prednisone 2.5 mg or more for 3 months or longer → calcium and vitamin D, fracture risk assessment, bisphosphonate by risk
Bile-acid sequestrant or orlistat → fat-soluble vitamin loss; give other drugs and vitamins hours apart
Levodopa wearing off after high-protein meals → amino acids compete for uptake; dose 30 minutes before meals or move protein to evening
Statin plus red yeast rice → the supplement contains lovastatin; double statin exposure and myopathy risk
Hypertension and low potassium in a heavy black licorice eater → mineralocorticoid excess; stop the licorice
Unexplained liver injury → ask about green tea extract, turmeric, ashwagandha, kava, and bodybuilding or weight-loss products
Elective surgery planned → stop bleeding-risk supplements (ginkgo, garlic, ginseng, fish oil, vitamin E) about 1–2 weeks before
SGLT2 inhibitor with a ketogenic or very low carbohydrate diet → euglycemic ketoacidosis risk; avoid the combination
Thiazide plus calcium carbonate and vitamin D → hypercalcemia; heavy carbonate use can cause milk-alkali syndrome with alkalosis and kidney injury
Drugs given by feeding tube → never crush extended-release or enteric-coated tablets; use liquid or immediate-release forms and flush
Doxycycline, potassium chloride, bisphosphonate or NSAID tablets → full glass of water and stay upright to prevent pill esophagitis

Traps that cost points

Telling a warfarin patient to stop eating green vegetables→ Steady intake matters, not avoidance. Dose warfarin to the usual diet and recheck INR after big diet changes.
Raising levothyroxine when TSH rose after an iron supplement started→ Iron binds levothyroxine in the gut; separate by 4 hours and recheck TSH in 6–8 weeks first.
Missing St John's wort in a transplant patient with rising creatinine→ It lowers tacrolimus and cyclosporine levels and can trigger rejection; ask about herbal products at every visit.
Keeping simvastatin in a patient who drinks grapefruit juice daily and has myalgias→ Grapefruit raises simvastatin levels and myopathy risk; switch to pravastatin or rosuvastatin or stop the grapefruit.
Advising a patient on apixaban to avoid salads→ Vitamin K does not affect DOACs; only warfarin needs consistent vitamin K intake.
Crushing extended-release nifedipine for a gastrostomy tube→ Crushing dumps the whole dose at once and can cause severe hypotension; switch to an immediate-release or liquid alternative.
Giving ciprofloxacin at the same time as calcium or tube feeds→ Divalent cations chelate the drug and cause treatment failure; separate the dose by several hours or choose another route.
Skipping supplement questions because they are natural→ Supplements cause bleeding, liver injury, interactions and false lab results; list them with prescriptions at every visit.