Nutrition

Nutrition is the process by which the body ingests, digests, absorbs, transports, metabolizes, and excretes food substances. For nurses, nutrition is both an assessment domain and a treatment modality. This article covers the content most heavily tested on the NCLEX-RN and NCLEX-PN examinations: macronutrients and micronutrients, nutritional assessment, therapeutic diets, enteral and parenteral nutrition, nutrition across the lifespan, and nutrition-related laboratory values.

Why Nutrition Matters in Nursing Practice

Nutritional status influences almost every clinical outcome a nurse monitors.

• Wound healing. Protein, vitamin C, vitamin A, and zinc are required for collagen synthesis and epithelialization. A protein-depleted patient will not heal a surgical incision or a stage 3 pressure injury no matter how good the dressing technique is.
• Immune function. Protein-energy malnutrition reduces lymphocyte counts and impairs cell-mediated immunity, raising infection risk.
• Skin integrity. Malnutrition plus immobility is the classic setup for pressure injury.
• Drug handling. Low serum albumin means fewer binding sites for highly protein-bound drugs (phenytoin, warfarin, furosemide), leaving more free drug and increasing toxicity risk.
• Length of stay and mortality. Malnourished inpatients have longer stays, more complications, and higher mortality.

Nutrition screening on admission is a nursing responsibility. Red flags include unintentional weight loss, poor appetite lasting more than a few days, chewing or swallowing difficulty, nothing-by-mouth status beyond a few days, and pressure injuries or non-healing wounds. Any of these warrants a referral to the registered dietitian.

Macronutrients

Energy Yield

Nutrient	Calories per gram
Carbohydrate	4 kcal/g
Protein	4 kcal/g
Fat	9 kcal/g
Alcohol	7 kcal/g

Acceptable Macronutrient Distribution Ranges for adults are roughly 45 to 65 percent of calories from carbohydrate, 20 to 35 percent from fat, and 10 to 35 percent from protein.

Carbohydrates

Carbohydrates are the body's preferred energy source and the only fuel the brain and red blood cells use efficiently under normal conditions. They are classified as simple sugars (monosaccharides and disaccharides) and complex carbohydrates (starches and fiber).

• Roughly 130 g/day of carbohydrate is needed to prevent ketosis from fat breakdown.
• Fiber is the indigestible carbohydrate fraction. Recommended intake is about 25 g/day for women and 38 g/day for men.
  • Soluble fiber (oats, barley, legumes, apples, citrus, psyllium) slows gastric emptying, blunts postprandial glucose rise, and lowers LDL cholesterol.
  • Insoluble fiber (wheat bran, whole grains, vegetable skins) adds bulk and speeds transit, relieving constipation.

Nursing application: When increasing dietary fiber, increase fluid intake at the same time and advance the fiber gradually. Adding bran to the diet of a dehydrated or fluid-restricted patient can precipitate impaction or obstruction.

Proteins

Proteins supply amino acids for tissue building, enzymes, hormones, immune globulins, and oncotic pressure.

• Complete proteins contain all nine essential amino acids: meat, fish, poultry, eggs, dairy, soy, and quinoa.
• Incomplete proteins are missing one or more essential amino acids. Plant proteins are combined over the course of the day (rice and beans, peanut butter and whole wheat bread, hummus and pita) to supply the full complement. They do not have to be eaten in the same meal.
• Baseline adult requirement is about 0.8 g/kg/day. Needs rise to roughly 1.2 to 2.0 g/kg/day with major burns, sepsis, trauma, large wounds, and pressure injuries.
• Protein is restricted in advanced chronic kidney disease that is not yet on dialysis, and in some cases of acute hepatic encephalopathy. Protein is increased once a patient starts hemodialysis or peritoneal dialysis because amino acids are lost into the dialysate.

Nursing application: A vegan patient is at particular risk for vitamin B12, iron, calcium, vitamin D, zinc, and omega-3 deficiency. Vitamin B12 occurs naturally only in animal foods, so supplementation or fortified foods are required, not optional.

Fats

Fats supply concentrated energy, carry the fat-soluble vitamins A, D, E, and K, and provide essential fatty acids.

• Saturated fat (animal fat, butter, coconut and palm oil) raises LDL cholesterol. Limit to less than 10 percent of calories, and less than 6 percent for patients with cardiovascular disease.
• Trans fat (partially hydrogenated oils) raises LDL and lowers HDL. Intake should be as close to zero as possible.
• Unsaturated fats are preferred. Monounsaturated fat comes from olive oil, canola oil, avocado, and nuts. Polyunsaturated fat includes the omega-3 fatty acids found in salmon, mackerel, sardines, walnuts, and flaxseed, which lower triglycerides.
• Dietary cholesterol comes only from animal sources. Plant foods contain no cholesterol.

Micronutrients

Fat-Soluble Vitamins (A, D, E, K)

Fat-soluble vitamins are stored in the liver and adipose tissue, so deficiency develops slowly and toxicity is possible with megadoses. Absorption depends on bile and pancreatic lipase, so patients with fat malabsorption, cholestasis, cystic fibrosis, or bariatric surgery are at risk of deficiency.

Vitamin	Key function	Deficiency	Food sources
A (retinol)	Vision, epithelial integrity, immunity	Night blindness, xerophthalmia, dry skin	Liver, egg yolk, dairy, orange and dark green vegetables (beta carotene)
D (calciferol)	Calcium and phosphorus absorption, bone mineralization	Rickets in children, osteomalacia and osteoporosis in adults	Fortified milk, fatty fish, egg yolk, sunlight exposure
E (tocopherol)	Antioxidant, protects cell membranes	Hemolytic anemia (notably in preterm infants), neuropathy	Vegetable oils, nuts, seeds, wheat germ
K	Synthesis of clotting factors II, VII, IX, X, and proteins C and S	Bleeding, prolonged PT/INR	Green leafy vegetables, broccoli, Brussels sprouts; also made by gut flora

Nursing application (high yield): Patients on warfarin should keep vitamin K intake consistent, not eliminated. Wildly varying green vegetable intake destabilizes the INR. A sudden large salad increases vitamin K and lowers the INR, raising clot risk; abruptly stopping greens raises the INR and bleeding risk.

Nursing application: Prolonged broad-spectrum antibiotic therapy kills vitamin K-producing gut flora and can prolong the PT/INR. Newborns receive intramuscular phytonadione (vitamin K) at birth because the gut is sterile and stores are low.

Water-Soluble Vitamins (B Complex and C)

Water-soluble vitamins are minimally stored and are excreted in urine, so deficiency appears relatively quickly and toxicity is less common (though pyridoxine and niacin do have toxic syndromes). They are heat labile and leach into cooking water, so steaming or microwaving preserves more than boiling.

Vitamin	Deficiency syndrome	Notes and sources
B1 thiamine	Beriberi; Wernicke encephalopathy and Korsakoff syndrome	Chronic alcohol use is the classic risk. Give thiamine before or with glucose to avoid precipitating Wernicke encephalopathy. Pork, whole grains, legumes.
B2 riboflavin	Cheilosis, angular stomatitis, glossitis	Milk, eggs, enriched grains. Destroyed by light, hence opaque milk containers.
B3 niacin	Pellagra: dermatitis, diarrhea, dementia, and if untreated death	Meat, fish, peanuts. High-dose niacin lowers LDL but causes flushing; aspirin 30 minutes prior reduces flushing.
B6 pyridoxine	Peripheral neuropathy, seizures, sideroblastic anemia	Isoniazid depletes B6, so pyridoxine is co-prescribed. Excess B6 itself causes sensory neuropathy.
B9 folate	Megaloblastic anemia without neurologic deficits; neural tube defects in the fetus	Leafy greens, legumes, fortified grains, liver, citrus. Depleted by methotrexate, phenytoin, and alcohol.
B12 cobalamin	Megaloblastic anemia with neurologic deficits (paresthesias, ataxia, decreased proprioception)	Requires intrinsic factor from gastric parietal cells. Pernicious anemia, gastrectomy, ileal resection, and long-term proton pump inhibitor or metformin use cause deficiency. Animal foods only.
C ascorbic acid	Scurvy: bleeding gums, poor wound healing, petechiae, loose teeth	Enhances non-heme iron absorption. Citrus, strawberries, tomatoes, peppers, broccoli.

Nursing application: Folate supplementation can correct the anemia of B12 deficiency while the neurologic damage silently progresses. Never treat a megaloblastic anemia with folate alone until B12 status is known.

Key Minerals

Mineral	Function	Deficiency or excess	Sources
Iron	Hemoglobin and myoglobin oxygen transport	Microcytic hypochromic anemia, fatigue, pallor, spoon nails	Heme iron from red meat, liver, and shellfish is best absorbed. Non-heme iron from beans, spinach, and fortified cereals is absorbed better with vitamin C and worse with tea, coffee, calcium, and antacids.
Calcium	Bone, muscle contraction, clotting, nerve conduction	Tetany, positive Chvostek and Trousseau signs, osteoporosis	Dairy, fortified plant milks, sardines with bones, tofu, kale, broccoli
Potassium	Cardiac and skeletal muscle conduction	Dysrhythmias, weakness, ileus at either extreme	Bananas, oranges, potatoes, tomatoes, avocado, spinach, dried fruit, legumes, salt substitutes
Sodium	Fluid balance, nerve impulse transmission	Excess drives fluid retention and hypertension	Table salt, processed and canned foods, cured meats, cheese, condiments
Magnesium	Enzyme cofactor, neuromuscular function	Tremor, tetany, torsades de pointes, refractory hypokalemia	Nuts, seeds, whole grains, leafy greens, legumes
Phosphorus	Bone, ATP, cell membranes	Restricted in chronic kidney disease; hypophosphatemia is central to refeeding syndrome	Dairy, meat, nuts, legumes, cola beverages, processed foods with phosphate additives
Zinc	Wound healing, taste and smell, immunity	Delayed healing, loss of taste (hypogeusia), alopecia	Oysters, red meat, poultry, beans, nuts
Iodine	Thyroid hormone synthesis	Goiter, hypothyroidism, cretinism in infants	Iodized salt, saltwater fish, seaweed, dairy

Nursing application: Salt substitutes are potassium chloride. They are dangerous for patients with chronic kidney disease or on ACE inhibitors, angiotensin receptor blockers, or potassium-sparing diuretics such as spironolactone.

Nutritional Assessment

Anthropometrics

• Body mass index equals weight in kilograms divided by height in meters squared. Underweight is below 18.5, normal is 18.5 to 24.9, overweight is 25.0 to 29.9, and obesity is 30.0 and above. BMI does not distinguish muscle from fat and is unreliable in athletes, in older adults with sarcopenia, and in the presence of edema or ascites.
• Weight change is the single most useful bedside indicator. Unintentional loss of more than 5 percent of body weight in one month or more than 10 percent in six months is clinically significant malnutrition.
• Daily weights are the most accurate measure of fluid status. Weigh at the same time each day, on the same scale, with the same amount of clothing, after voiding. One kilogram of weight change equals approximately one liter of fluid, or about 2.2 pounds per liter.
• Waist circumference above 40 inches in men or above 35 inches in women indicates central adiposity and increased cardiometabolic risk.

Clinical and Dietary Assessment

Inspect hair, skin, nails, oral mucosa, gums, and conjunctiva. Assess dentition, fit of dentures, swallowing, appetite, and the ability to shop for and prepare food. Ask about food insecurity, cultural and religious food practices, food allergies, alcohol use, and supplement or herbal use. A 24-hour recall or a three-day food diary provides intake data.

Food, Drug, and Nutrient Interactions

• Warfarin and vitamin K: keep green vegetable intake consistent.
• Monoamine oxidase inhibitors and tyramine: aged cheeses, cured and smoked meats, fermented soy, tap and draft beer, red wine, sauerkraut, and overripe fruit can cause hypertensive crisis.
• Grapefruit juice inhibits intestinal CYP3A4 and raises levels of statins, many calcium channel blockers, and some immunosuppressants.
• Tetracyclines, fluoroquinolones, and levothyroxine bind to calcium, iron, magnesium, aluminum, and zinc. Separate from dairy, antacids, and mineral supplements. Levothyroxine is taken on an empty stomach 30 to 60 minutes before breakfast.
• Corticosteroids raise blood glucose and promote sodium retention, potassium loss, and bone loss.
• Loop and thiazide diuretics waste potassium and magnesium; potassium-sparing diuretics retain potassium.
• Metformin and proton pump inhibitors reduce vitamin B12 absorption over the long term.
• Alcohol displaces nutrient-dense calories and impairs thiamine, folate, and magnesium status.

Therapeutic Diets

Consistency and Texture Modifications

• Clear liquid: anything transparent and liquid at body temperature, such as broth, clear juice without pulp, gelatin, tea, black coffee, and popsicles. Not nutritionally adequate beyond a few days. Used pre-procedure and immediately post-op. Note that red or purple items are often avoided before colonoscopy because they mimic blood.
• Full liquid: adds milk, cream soups, ice cream, pudding, and all juices. Bridges clear liquid to soft.
• Mechanical soft and pureed: for chewing difficulty, poor dentition, or dysphagia. Texture is modified but the diet is otherwise unrestricted.
• Dysphagia diets and thickened liquids: thin liquids aspirate most easily. Liquids are thickened to nectar, honey, or pudding consistency per the speech language pathologist's recommendation. Position upright at 90 degrees, use a chin-tuck if instructed, avoid straws unless specifically ordered, allow adequate time, and check for pocketing in the cheeks after each bite. Keep the patient upright for at least 30 to 60 minutes after eating.

Cardiac and Hypertension Diets

• Sodium restriction is commonly 2 to 3 g/day for heart failure and hypertension. The largest source of dietary sodium is processed and restaurant food, not the salt shaker.
• The DASH pattern emphasizes fruits, vegetables, whole grains, low-fat dairy, poultry, fish, and nuts, and limits red meat, sweets, and sugar-sweetened beverages.
• Limit saturated fat to under 6 percent of calories, eliminate trans fat, and increase soluble fiber and omega-3 fatty acids.

Nursing application: Teach patients to read the Nutrition Facts label for sodium per serving and to check serving size. "Reduced sodium" only means 25 percent less than the original, which may still be a high-sodium food. Canned vegetables can be drained and rinsed to remove a meaningful fraction of the sodium.

Renal Diet

Nutrient	Chronic kidney disease, not on dialysis	On hemodialysis
Protein	Restricted, roughly 0.6 to 0.8 g/kg/day	Increased, roughly 1.2 g/kg/day
Sodium	Restricted, commonly 2 g/day	Restricted
Potassium	Restricted as serum level rises	Usually restricted
Phosphorus	Restricted; phosphate binders taken with meals	Restricted; binders with meals
Fluid	Usually not restricted early	Restricted, often 1000 mL/day plus urine output

High-potassium foods to limit include bananas, oranges and orange juice, potatoes, tomatoes and tomato products, avocado, spinach, dried fruit, melons, and salt substitutes. Lower-potassium alternatives include apples, berries, grapes, cranberry juice, cabbage, green beans, and cauliflower. Potatoes can be leached by peeling, dicing, and soaking or double-boiling.

High-phosphorus foods to limit include dairy, nuts, seeds, legumes, whole grains, chocolate, organ meats, dark cola beverages, and processed foods with phosphate additives.

Nursing application: Phosphate binders such as calcium acetate and sevelamer must be taken with food to bind dietary phosphorus in the gut. Taken between meals, they do nothing.

Diabetic Diet

• The modern standard is consistent carbohydrate intake distributed across meals rather than a rigid "no sugar" diet. Total carbohydrate matters more than the type.
• Carbohydrate counting typically uses 15 g of carbohydrate per exchange.
• Emphasize whole grains, legumes, non-starchy vegetables, and lean protein. Limit sugar-sweetened beverages, which raise glucose fastest.
• Alcohol taken without food can cause delayed hypoglycemia because it suppresses hepatic gluconeogenesis. Patients on insulin or sulfonylureas should eat carbohydrate with alcohol.
• Treat hypoglycemia in a conscious patient with the rule of 15: 15 g of fast-acting carbohydrate (4 ounces of juice or regular soda, glucose tablets, or 1 tablespoon of honey), recheck in 15 minutes, and repeat if still below 70 mg/dL. Follow with a protein and carbohydrate snack if the next meal is more than an hour away.

Nursing application: Sick-day rules matter. Patients must continue insulin during illness even if eating poorly, monitor glucose more often, check ketones, and take carbohydrate-containing liquids.

Gastrointestinal Diets

• Low-residue or low-fiber: for acute diverticulitis, active inflammatory bowel disease flares, bowel prep, and early post-operative bowel recovery. Avoid whole grains, raw fruits and vegetables, nuts, seeds, and legumes.
• High-fiber: for diverticulosis (prevention), constipation, and irritable bowel syndrome with constipation. Do not confuse this with diverticulitis, which requires low fiber during the acute flare and a return to high fiber after resolution.
• Gluten-free (celiac disease): strictly eliminate wheat, rye, and barley. Safe grains include rice, corn, quinoa, buckwheat, millet, amaranth, and certified gluten-free oats. Cross-contamination from shared toasters, fryers, and cutting boards is a real cause of ongoing symptoms.
• Lactose-restricted: lactose-free milk, hard aged cheeses, and yogurt with live cultures are often tolerated. Ensure alternative calcium and vitamin D sources.
• GERD: small frequent meals, avoid eating within 3 hours of lying down, elevate the head of the bed, and limit caffeine, chocolate, peppermint, alcohol, fatty or fried food, citrus, tomato, and carbonated beverages. Weight loss and smoking cessation help most.
• Dumping syndrome (after gastrectomy or bariatric surgery): small frequent meals, high protein, moderate fat, low simple carbohydrate, fluids taken between meals rather than with meals, and lying down or reclining for 20 to 30 minutes after eating.
• Hepatic disease: restrict sodium and often fluid when ascites is present. Provide adequate protein and calories; blanket protein restriction in cirrhosis is no longer standard and worsens muscle wasting. Small frequent meals with a late evening snack reduce catabolism.
• Pancreatitis: nothing by mouth during severe acute episodes, then advance to a low-fat diet. Alcohol is eliminated. Pancreatic enzyme replacement is taken with meals and snacks in chronic pancreatitis.
• Gout: limit high-purine foods such as organ meats, anchovies, sardines, shellfish, red meat, and beer. Encourage generous fluid intake.

Other Modified Diets

• Neutropenic or low-microbial diet: avoid raw or undercooked meat, fish, and eggs, unpasteurized dairy and juice, and often raw fruits and vegetables that cannot be peeled. Practices vary by institution.
• Bland diet: avoids highly seasoned, fried, and gas-forming foods.
• Ketogenic diet: high fat, adequate protein, very low carbohydrate; used for refractory pediatric epilepsy. Monitor for constipation, kidney stones, growth impairment, and hyperlipidemia.

Enteral Nutrition

Enteral nutrition delivers formula directly into the gastrointestinal tract. The governing principle is: if the gut works, use it. Enteral feeding preserves gut mucosal integrity, reduces bacterial translocation, costs less, and carries lower infection risk than parenteral nutrition.

Access Routes

• Nasogastric and orogastric tubes: short-term, generally under 4 to 6 weeks.
• Nasoduodenal and nasojejunal tubes: post-pyloric placement for patients with gastroparesis, high aspiration risk, or pancreatitis.
• Gastrostomy (PEG) and jejunostomy (PEJ) tubes: long-term access placed surgically, endoscopically, or radiologically.

Delivery Methods

• Bolus: a set volume delivered over about 15 minutes by syringe several times daily. Most physiologic and allows mobility, but is least tolerated.
• Intermittent: a set volume over 30 to 60 minutes by gravity or pump.
• Continuous: pump-delivered over 12 to 24 hours. Best tolerated and required for post-pyloric feeding, because the small bowel has no reservoir capacity.
• Cyclic: continuous infusion over a compressed window, often overnight, to allow daytime freedom or to promote appetite.

Nursing Management of Tube Feeding

1. Verify placement. Radiographic confirmation is the gold standard after initial insertion of a blindly placed tube and before the first use. Thereafter, check the exit-site marking on the tube, measure the external tube length, and assess gastric aspirate. Auscultating an air bolus over the epigastrium is not a reliable method and is no longer recommended. Gastric aspirate pH is typically 5.5 or lower, though acid-suppressing medications raise it.
2. Elevate the head of the bed to 30 to 45 degrees during feeding and for at least 30 to 60 minutes afterward. This is the single most important aspiration precaution.
3. Check gastric residual volume per institutional policy, typically every 4 to 6 hours during continuous feeding. Current guidance from professional societies is not to hold feeding for a residual under 500 mL in the absence of other signs of intolerance, but many facilities still use 250 to 500 mL thresholds. Return the aspirate unless policy directs otherwise, since discarding it discards electrolytes.
4. Flush the tube with 30 mL of water before and after each feeding and each medication, every 4 hours during continuous feeding, and any time the feeding is interrupted. Water is the flush of choice. Cranberry juice and cola are not effective and can worsen clogging.
5. Give medications separately. Crush immediate-release tablets finely and dissolve them, or use liquid forms. Never crush enteric-coated, sustained-release, or extended-release formulations. Flush between each medication.
6. Hang time. Discard open ready-to-hang formula per policy, generally within 24 to 48 hours for closed systems and within 4 to 8 hours for decanted or reconstituted formula. Change the administration set every 24 hours.
7. Formula temperature. Administer at room temperature. Cold formula causes cramping and diarrhea.
8. Monitor daily weight, intake and output, glucose, electrolytes, bowel pattern, and abdominal distention.

Complications

Complication	Cause	Nursing action
Aspiration pneumonia	Reflux of formula, flat positioning, impaired gag reflex	Stop the feeding immediately, turn the patient to the side, suction, administer oxygen, assess breath sounds and oxygen saturation, and notify the provider. This is the priority complication.
Diarrhea	Rapid infusion rate, hyperosmolar formula, cold formula, sorbitol-containing or hyperosmolar medications, antibiotic-associated Clostridioides difficile, low fiber	Slow the rate, check medications, obtain stool studies if infection is suspected, consider a fiber-containing formula
Constipation	Inadequate free water or fiber, immobility, opioids	Increase free water flushes, consider fiber formula, mobilize
Tube occlusion	Inadequate flushing, crushed medications, formula residue	Flush with warm water using a gentle push-pull technique with a large syringe. Never force with a small-barrel syringe, which generates high pressure and can rupture the tube.
Dehydration and hypernatremia	Insufficient free water; formula is not all water	Calculate and provide free water; monitor sodium and BUN
Hyperglycemia	High carbohydrate load, stress response, steroids	Monitor glucose, adjust formula or insulin
Nausea and high residuals	Delayed gastric emptying, rapid rate	Reduce rate, consider post-pyloric access or a prokinetic agent
Tube dislodgement	Traction, agitation	For a mature gastrostomy tract, cover and notify the provider promptly, since the stoma can begin to close within hours. Do not blindly reinsert unless trained and authorized.

Parenteral Nutrition

Parenteral nutrition delivers nutrients intravenously, bypassing the gastrointestinal tract entirely. It is indicated when the gut is nonfunctional or inaccessible: short bowel syndrome, bowel obstruction, high-output enterocutaneous fistula, severe malabsorption, prolonged ileus, or intractable vomiting.

TPN Versus PPN

• Total parenteral nutrition is hypertonic, commonly greater than 10 percent dextrose and above roughly 900 mOsm/L, so it requires a central venous access device with the tip in the superior vena cava. Peripheral administration of TPN causes severe phlebitis and vein destruction.
• Peripheral parenteral nutrition uses lower dextrose concentrations and lower osmolarity for short-term partial support through a peripheral line.
• Solutions contain dextrose, crystalline amino acids, electrolytes, vitamins, and trace elements. Lipid emulsions supply essential fatty acids and calorie density and may be piggybacked or included in a three-in-one admixture.

Nursing Management of TPN

1. Confirm central line tip placement by X-ray before the first infusion of a newly placed central catheter.
2. Use a dedicated lumen. Do not infuse other medications, blood products, or draw blood from the TPN lumen unless policy explicitly permits it.
3. Use an infusion pump and an in-line filter (typically 0.22 micron for lipid-free solutions and 1.2 micron for lipid-containing admixtures).
4. Change the bag and tubing every 24 hours using strict aseptic technique. Refrigerate solution until use and remove it about 30 to 60 minutes before hanging.
5. Inspect the bag before hanging. Discard if cloudy, discolored, or containing precipitate, and never add anything to the bag on the unit.
6. Monitor capillary glucose every 4 to 6 hours, at least initially. Hyperglycemia is the most common metabolic complication, and sliding-scale insulin is frequently required.
7. Start slowly and taper off slowly. Initiate at a reduced rate and titrate up over 24 to 48 hours. Never abruptly discontinue TPN, because the sustained endogenous insulin response causes rebound hypoglycemia. Taper the rate down, and if the bag runs out or the line fails, hang 10 percent dextrose in water at the same rate and notify the provider.
8. Never "catch up" a TPN infusion that has fallen behind by increasing the rate, and never slow it abruptly. Both destabilize glucose.
9. Monitor daily weight, strict intake and output, electrolytes, BUN and creatinine, liver function tests, triglycerides, and complete blood count.
10. Assess the insertion site every shift for redness, drainage, tenderness, and swelling. TPN is an excellent bacterial growth medium and catheter-related bloodstream infection is the most common serious complication. A new fever in a patient on TPN is a catheter-related bloodstream infection until proven otherwise.

Key Complications

• Catheter-related bloodstream infection: fever, chills, elevated white blood cell count, site erythema. Obtain blood cultures from the catheter and a peripheral site, and notify the provider.
• Hyperglycemia from excessive dextrose delivery, and rebound hypoglycemia from abrupt cessation.
• Air embolism during tubing or cap changes. Signs are sudden dyspnea, chest pain, hypotension, and tachycardia. Immediately clamp the catheter, place the patient in left lateral Trendelenburg position, administer 100 percent oxygen, and call for help.
• Pneumothorax during subclavian insertion. Assess for sudden dyspnea, chest pain, and diminished unilateral breath sounds.
• Fluid overload from too-rapid infusion, particularly in heart failure and kidney disease.
• Hepatic complications including steatosis and cholestasis with prolonged use.

Refeeding Syndrome

Refeeding syndrome is a potentially fatal shift of fluid and electrolytes when nutrition is reintroduced to a severely malnourished patient. Insulin surges in response to the carbohydrate load and drives phosphate, potassium, and magnesium intracellularly.

• Hallmark finding: hypophosphatemia. Also hypokalemia, hypomagnesemia, thiamine depletion, and sodium and fluid retention.
• Consequences: cardiac dysrhythmias, heart failure, respiratory muscle failure, rhabdomyolysis, seizures, and death.
• At-risk patients: anorexia nervosa, chronic alcohol use disorder, prolonged fasting or nothing-by-mouth status, cancer cachexia, malabsorption, and the older adult with prolonged poor intake.
• Prevention: start feeding at low calorie loads and advance slowly over days, supplement thiamine before feeding begins, correct electrolytes before and during initiation, and monitor phosphorus, potassium, and magnesium closely along with cardiac rhythm and fluid status.

Nutrition Across the Lifespan

Infancy (birth to 12 months)

• Energy needs are roughly 100 to 110 kcal/kg/day in early infancy, far higher per kilogram than at any later stage.
• Breast milk or iron-fortified formula is the sole source of nutrition for about the first 6 months. Exclusively and partially breastfed infants receive 400 IU/day of supplemental vitamin D beginning shortly after birth.
• Introduce iron-fortified single-grain cereal and pureed foods around 6 months, when the infant can sit with support, has good head control, and has lost the extrusion reflex. Introduce one new food at a time and wait 3 to 5 days to identify allergic reactions.
• No honey before 12 months because of the risk of infant botulism.
• No cow's milk before 12 months. It causes occult gastrointestinal blood loss, is low in iron, and presents an excessive renal solute load. Whole milk is given from 12 to 24 months for brain development.
• Avoid choking hazards: whole grapes, nuts, popcorn, hot dog rounds, hard candy, raw carrot pieces, and spoonfuls of peanut butter.
• Never prop a bottle or put the infant to bed with a bottle, because of aspiration risk, otitis media, and early childhood caries.
• Expected growth: birth weight doubles by about 6 months and triples by 12 months.

Toddler and Preschool

• Growth slows and appetite drops. Physiologic anorexia is normal and reassurance is the intervention.
• Food jags, ritualism, and picky eating are developmentally normal. Offer small portions, roughly 1 tablespoon of each food per year of age, allow self-feeding, avoid using food as reward or punishment, and do not short-order cook.
• Limit milk to about 16 to 24 ounces per day to prevent milk anemia from displacing iron-rich foods.
• Screen for iron deficiency anemia and lead exposure. Adequate iron and calcium intake reduce lead absorption.

School Age and Adolescence

• Adolescence brings the second-fastest growth period and the highest calorie, protein, calcium, and iron needs of childhood. Menstruating girls need more iron.
• Peak bone mass is built during adolescence, so calcium and vitamin D intake now determines fracture risk decades later. Sugar-sweetened and carbonated beverages displace milk.
• Screen for eating disorders, disordered eating in athletes, and skipped meals.

Pregnancy and Lactation

• Folic acid 400 mcg/day for all people capable of pregnancy and 600 mcg/day during pregnancy prevents neural tube defects. The neural tube closes by about day 28, often before pregnancy is recognized, so preconception intake is what matters. People with a prior affected pregnancy require a much higher prescribed dose.
• Calorie needs increase by roughly 340 kcal/day in the second trimester and 450 kcal/day in the third, and by about 450 to 500 kcal/day during lactation. There is no meaningful increase in the first trimester.
• Iron demand roughly doubles; supplementation is routine. Take iron with vitamin C and on an empty stomach if tolerated, and expect dark stools and constipation.
• Recommended total gain for a woman with a normal pre-pregnancy BMI is about 25 to 35 pounds.
• Avoid alcohol entirely, high-mercury fish (shark, swordfish, king mackerel, tilefish), raw or undercooked fish, meat, and eggs, unpasteurized milk and soft cheeses, unheated deli meats and hot dogs, and raw sprouts, because of listeriosis and toxoplasmosis risk. Limit caffeine to about 200 mg/day.
• Encourage 8 to 12 ounces per week of low-mercury fish such as salmon, sardines, and canned light tuna for omega-3 fatty acids.
• Manage morning sickness with dry crackers before rising, small frequent meals, and separating fluids from solids.

Older Adults

• Calorie needs fall with reduced lean body mass and activity, but protein, calcium, vitamin D, and vitamin B12 needs stay the same or rise. Nutrient density becomes the priority.
• Thirst sensation is blunted, making dehydration the most common fluid and electrolyte disorder in this population. Offer fluids on a schedule rather than waiting for the patient to ask.
• Atrophic gastritis reduces gastric acid and impairs vitamin B12 absorption from food. Fortified foods or supplements are recommended.
• Barriers to intake include poor dentition and ill-fitting dentures, xerostomia from polypharmacy, diminished taste and smell, dysphagia, depression, social isolation, functional limits on shopping and cooking, and fixed income.
• Sarcopenia responds to adequate protein spread across meals plus resistance activity.
• Nursing application: Rather than adding salt to make food palatable for a patient on a sodium restriction, use herbs, spices, lemon juice, and vinegar.

Nutrition-Related Laboratory Values

Test	Typical adult reference range	Nutritional significance
Albumin	3.5 to 5.0 g/dL	Half-life about 18 to 21 days, so it reflects long-standing status. Falsely low with inflammation, liver disease, nephrotic syndrome, and fluid overload; falsely high with dehydration. It is better understood as an inflammation marker than a pure nutrition marker.
Prealbumin (transthyretin)	15 to 36 mg/dL	Half-life 2 to 3 days, so it responds quickly and is used to track short-term response to nutrition support. Also depressed by inflammation.
Transferrin	200 to 400 mg/dL	Half-life 8 to 10 days; also rises in iron deficiency, which confounds interpretation.
Total lymphocyte count	1500 to 3000 cells/mm³	Falls with protein-energy malnutrition; reflects immune competence.
Hemoglobin	14 to 18 g/dL (male), 12 to 16 g/dL (female)	Low in iron, B12, and folate deficiency
Hematocrit	42 to 52 percent (male), 37 to 47 percent (female)	Elevated with dehydration, low with anemia and overhydration
Serum iron and ferritin	Ferritin 12 to 300 ng/mL (varies by sex and lab)	Ferritin is the best indicator of iron stores but is an acute phase reactant and rises with inflammation
BUN	10 to 20 mg/dL	Rises with high protein intake, dehydration, and gastrointestinal bleeding; falls with low protein intake and liver failure
Creatinine	0.6 to 1.2 mg/dL	Reflects renal function and muscle mass
Serum sodium	135 to 145 mEq/L	Reflects water balance more than salt intake
Serum potassium	3.5 to 5.0 mEq/L	Critical for renal and diuretic-treated patients
Serum phosphorus	3.0 to 4.5 mg/dL	Falls sharply in refeeding syndrome; rises in chronic kidney disease
Serum magnesium	1.3 to 2.1 mEq/L	Falls in refeeding syndrome, alcohol use disorder, and diuretic therapy
Total calcium	9.0 to 10.5 mg/dL	Interpret against albumin; low albumin falsely lowers total calcium while ionized calcium stays normal
Fasting glucose	70 to 99 mg/dL	100 to 125 mg/dL is prediabetes; 126 mg/dL or higher on two occasions is diabetes
Hemoglobin A1C	Below 5.7 percent normal	5.7 to 6.4 percent prediabetes; 6.5 percent or higher diabetes. A common treatment goal is below 7 percent, individualized.
Total cholesterol	Below 200 mg/dL desirable	Screening lipid marker
LDL cholesterol	Below 100 mg/dL optimal	Below 70 mg/dL for very high cardiovascular risk
HDL cholesterol	Above 40 mg/dL (male), above 50 mg/dL (female)	Higher is protective
Triglycerides	Below 150 mg/dL	Responsive to alcohol, simple sugars, and weight; monitored during lipid infusion in parenteral nutrition

Nursing application: Prealbumin, not albumin, is the value to trend when evaluating whether a patient is responding to nutrition support over the course of a week. Both must be interpreted alongside C-reactive protein or clinical inflammation, because acute illness suppresses both independent of intake.

Cultural, Religious, and Ethical Considerations

• Diet is deeply cultural. Assess food preferences and restrictions rather than assuming them from ethnicity or a chart label.
• Common religious patterns include kosher practice (no pork or shellfish, no mixing meat and dairy), halal practice (no pork or alcohol, ritual slaughter), Hindu vegetarianism and avoidance of beef, Seventh-day Adventist vegetarianism, and fasting periods in Islam, Judaism, and Christianity. Illness generally exempts a person from religious fasting obligations, but this is the patient's decision to make.
• Jehovah's Witnesses refuse blood products, which is relevant to nutrition support because albumin infusions and some products are derived from blood.
• Artificial nutrition and hydration are medical treatments that a competent patient or an authorized surrogate may accept or refuse. Advance directives frequently address feeding tubes specifically. The nurse's role is to ensure the patient's documented wishes are known and honored, and to escalate conflicts to the care team and ethics resources.

High-Yield Test-Taking Points

• If a tube-fed patient coughs, chokes, or becomes short of breath, stop the feeding first, then position, suction, oxygenate, and notify.
• Never abruptly stop TPN. Hang 10 percent dextrose in water and notify the provider.
• Head of bed at 30 to 45 degrees is the single best aspiration precaution during and after enteral feeding.
• Refeeding syndrome equals hypophosphatemia. Start low and go slow, and give thiamine.
• Diverticulitis means low fiber during the flare; diverticulosis means high fiber for prevention.
• Warfarin means consistent vitamin K, not zero vitamin K.
• Phosphate binders go with meals.
• Protein is restricted before dialysis and increased once dialysis begins.
• Salt substitutes are potassium and are dangerous in kidney disease and with potassium-sparing agents.
• No honey and no cow's milk before 12 months of age.
• Daily weight is the most reliable indicator of fluid status; 1 kg equals about 1 L.
• Vitamin C with iron increases absorption; calcium, antacids, tea, and coffee decrease it.
• Give thiamine before or with glucose in a patient with alcohol use disorder.

This page is independent study material for nursing licensure exam preparation. NCLEX-RN® and NCLEX-PN® are registered trademarks of the National Council of State Boards of Nursing (NCSBN). This content is not produced, reviewed, or endorsed by NCSBN. Always verify clinical information against current facility policy, drug references, and your nursing program's curriculum before applying it in practice.