Vitamin deficiencies

• Vitamin deficiency is common in emergency and hospital medicine even in well-nourished countries, because alcohol use, poor diet, malabsorption, chronic disease and critical illness all deplete stores.
• The vitamins you will actually see deficient are thiamine (beriberi and Wernicke-Korsakoff), folate and vitamin B12 (megaloblastic anaemia and neuropathy), vitamin C (scurvy), niacin (pellagra), vitamin D (rickets and osteomalacia) and vitamin A (night blindness and xerophthalmia); zinc, iodine and iron are the common minerals.
• Many deficiencies look like something else: scurvy mimics vasculitis, pellagra mimics alcohol withdrawal, and B12 deficiency can present with neuropsychiatric disease without anaemia.
• When in doubt, treat empirically with the relevant vitamin before confirming the diagnosis; thiamine in particular must be given before glucose and before refeeding.
• Prevention rests on food fortification (salt iodisation, vitamin A supplementation programmes), adequate diet, bariatric follow-up and multivitamin support in malabsorption.

By the end of this page you should be able to:

1. Recognise the clinical syndromes produced by deficiency of the major vitamins and minerals.
2. Explain the risk groups and mechanisms, including malabsorption and bariatric surgery.
3. Diagnose deficiency using the appropriate first test, without over-testing.
4. Start safe replacement and name the doses used for thiamine, niacin, folate, B12, vitamins A, C and D.
5. Prevent and manage refeeding syndrome during nutritional repletion.
6. Outline the global burden of vitamin deficiency and the prevention programmes that reduce it.

This page is written for the first-time reader meeting micronutrient deficiency as a clinical topic. It covers deficiencies of the vitamins and minerals that matter in acute and general medicine, organised by presentation rather than by pathway: how the patient looks, who is at risk, how to confirm the diagnosis, what to give, and what not to miss. Deficiency of a single vitamin is often the tip of wider malnutrition, so always think about the diet, the gut, the liver and the alcohol history together.

Vitamin deficiency should be considered in four overlapping groups.

1. Poor intake. Alcohol use disorder, food insecurity, fad or exclusion diets, anorexia and institutional or isolated living. In these patients thiamine, vitamin C, niacin and folate are the usual culprits. ^[8]
2. Malabsorption and maldigestion. Coeliac disease, Crohn's disease, chronic pancreatitis, cholestasis, ileal resection and short bowel. Fat-soluble vitamins (A, D, E, K) and B12 are most affected. ^[3]
3. Increased requirement or loss. Pregnancy, lactation, childhood growth, haemodialysis, diuretics, large burns, critical illness and sepsis. ^[8]
4. Iatrogenic and post-surgical. Bariatric surgery, gastrectomy, ileal resection, prolonged proton pump inhibitor or metformin use, isoniazid, methotrexate and other drugs. ^[2][9]

High-priority, potentially dangerous situations are Wernicke-Korsakoff syndrome, refeeding syndrome, megaloblastic anaemia with neurological signs, severe or bleeding scurvy, and deficiency after bariatric surgery.

• Confusion, ataxia or abnormal eye movements in a malnourished or alcoholic patient: treat for thiamine deficiency before glucose. ^[6]
• A photosensitive rash with confusion and diarrhoea after heavy alcohol use or malnutrition: pellagra, not alcohol withdrawal. ^[7]
• Macrocytic anaemia with numbness, ataxia or cognitive change: B12 deficiency may be present without anaemia; do not give folate alone. ^[2][6]
• Bleeding with a normal platelet count and normal coagulation ratios in a malnourished patient: consider vitamin K (and vitamin C) deficiency. ^[3]
• A post-bariatric patient with vomiting and confusion: thiamine deficiency until proven otherwise. ^[9]
• Rapidly falling phosphate, potassium or magnesium after refeeding: refeeding syndrome. ^[1]
• Night blindness, xerophthalmia or keratomalacia: vitamin A deficiency, which worsens with concurrent zinc deficiency. ^[4]

A good dietary and risk history is the diagnostic test for most vitamin deficiencies. Ask about the diet (vegan or vegetarian, alcohol, energy drinks and "beige" shelf-stable foods), weight change, gastrointestinal surgery, chronic diarrhoea or vomiting, drug use (metformin, proton pump inhibitors, H2 blockers, isoniazid, methotrexate, anticonvulsants), and social circumstances (food insecurity, isolation, institutional care). ^[2][8] Ask about herbal or over-the-counter supplements, which can both cause and mask deficiency. In pregnancy and breastfeeding, requirements rise sharply and stored vitamin A in particular becomes risky in excess.

Dietary clues are followed by syndromic signs.

• Vitamin A: reduced night vision, xerophthalmia, Bitot spots, keratomalacia, dry scaly skin (phrynoderma), and recurrent infection. ^[3][4]
• B1 (thiamine): high-output or dilated cardiomyopathy (wet beriberi) or painful peripheral neuropathy, ataxia and confusion (dry beriberi, Wernicke). ^[6][8]
• B2 (riboflavin): angular stomatitis, cheilitis, glossitis and dermatitis. ^[6]
• B3 (niacin): pellagra, the four Ds - dermatitis (photosensitive, Casal necklace), diarrhoea, dementia and, if untreated, death. ^[6][7]
• B6 (pyridoxine): microcytic anaemia, peripheral neuropathy and, in infants, irritability and seizures. ^[6]
• B7 (biotin): alopecia and a scaly periorificial rash, rarely. ^[6]
• B9/B12 (folate/cobalamin): megaloblastic anaemia, glossitis, and B12-related subacute combined degeneration (ataxia, peripheral neuropathy, cognitive change). ^[2][6]
• Vitamin C: perifollicular haemorrhage, corkscrew hairs, gingival bleeding and poor wound healing; anaemia that does not respond to iron. ^[5][8]
• Vitamin D: bone pain, proximal myopathy, rickets in children, osteomalacia and fractures in adults. ^[3]
• Vitamin E: posterior column and spinocerebellar degeneration and night blindness. ^[3]
• Vitamin K: mucocutaneous or visceral bleeding and osteopenia. ^[3]
• Zinc: acrodermatitis (perioral and perianal crusting), poor healing, alopecia; iodine: goitre and hypothyroidism; iron: pallor, koilonychia and dyspnoea; selenium: cardiomyopathy (Keshan disease) and myopathy. ^[8][10][11]

Investigate deficiency without delaying treatment in a sick patient.

• General: full blood count, blood film (macrocytosis, hypersegmented neutrophils, microcytosis), renal and liver function, albumin, phosphate, potassium and magnesium, and a C-reactive protein. ^[11]
• Thiamine: plasma or whole-blood thiamine and erythrocyte transketolase activity (most reliable); lactate may be raised. Do not wait for results before treating. ^[8]
• Vitamin B12: total cobalamin or active B12 (holotranscobalamin) first. Values under 180 ng per litre (133 pmol per litre) or active B12 under 25 pmol per litre confirm deficiency; 180 to 350 ng per litre (133 to 258 pmol per litre) or active B12 25 to 70 pmol per litre are indeterminate, in which case check methylmalonic acid. More than 350 ng per litre (258 pmol per litre) makes deficiency unlikely. Take the sample before repletion. ^[2]
• Folate: serum folate under 2 ng per millilitre indicates deficiency; 2 to 4 ng per millilitre is borderline. Use red cell folate where possible. ^[6]
• Vitamin C: fasting plasma ascorbate (under 11 micromol per litre suggests scurvy; 11 to 28 micromol per litre is marginal). Whole blood is preferred by some. ^[5][8]
• Vitamin A: serum retinol under 20 micrograms per decilitre supports deficiency; xerophthalmia is almost diagnostic. Serum can be normal when liver stores are low. ^[4]
• Vitamin D: serum 25-hydroxyvitamin D; values under 20 ng per millilitre (50 nmol per litre) are generally considered deficient and 20 to 30 ng per millilitre insufficient. Check calcium and parathyroid hormone for osteomalacia or rickets. ^[3]
• Iron: ferritin is the single best marker. Under 15 micrograms per litre means depleted stores and under 30 micrograms per litre low stores; ferritin is an acute-phase protein, so in inflammation use a cut-off of 100 micrograms per litre or check transferrin saturation (under 20 per cent). ^[11]
• Zinc: plasma zinc with compatible signs. Lower if inflamed but accurate with clinical findings. ^[8]
• Iodine: population median urinary iodine concentration; clinically, thyroid function tests and goitre assessment. ^[10]

The figure below is a teaching outline for adults; adapt it to your patient and follow local guidance.

This summary table covers the nutrients requested in the brief. Deficiency syndromes and doses come from the references above; use local formularies for exact products.

• Vitamin deficiency in adults is usually multifactorial: suspect it whenever the diet, gut, liver, drug history or social circumstances point that way. ^[8]
• Thiamine must be given before glucose and before refeeding; oral thiamine is not enough for Wernicke. ^[6]
• Pellagra is the great mimic of alcohol withdrawal and can present as delirium alone. ^[7]
• B12 deficiency can damage the nervous system without anaemia, so do not give folate until B12 has been checked. ^[2][6]
• Vitamin C deficiency (scurvy) presents with bleeding and anaemia and improves dramatically within 24 to 48 hours of replacement. ^[5]
• Vitamin A deficiency affects vision and immunity and is worsened by zinc deficiency. ^[4]
• Malabsorption, including bariatric surgery, requires lifelong multivitamin and mineral supplementation and monitoring. ^[9]
• Refeeding syndrome is prevented by "start low, go slow" and is treated by correcting electrolytes before increasing nutrition. ^[1]

Start replacement and correct the cause together.

• Thiamine (Wernicke-Korsakoff, beriberi). Give thiamine 500 mg intravenously three times daily for 3 days, then 250 mg intravenously or intramuscularly once daily for 5 days or until improvement stops; then oral thiamine 100 to 200 mg daily. Give before any carbohydrate. Prophylaxis in severe alcohol withdrawal, poor diet or malnutrition: 100 mg intravenously or intramuscularly once daily for 3 to 5 days. ^[6] An alternative evidence-based description uses 200 mg intravenously three times daily until improvement stops. ^[6]
• Niacin (pellagra). Give nicotinamide 100 mg orally every 6 hours until the rash and other acute symptoms resolve, then 50 mg every 8 to 12 hours until all skin lesions have healed; avoid sun and alcohol. A World Health Organization regimen gives 300 mg nicotinamide daily orally in divided doses, or 100 mg daily parenterally, for 3 to 4 weeks. ^[6][7]
• Vitamin C (scurvy). Adults: 300 to 1000 mg daily by mouth for one month; severe or bleeding cases 1000 mg intravenous ascorbic acid daily for 3 days, then 250 to 500 mg twice daily until recovery. Children: 100 mg three times daily for one week, then once daily for several weeks. ^[5] An alternative modern regimen uses 200 mg intravenous ascorbic acid for 7 days, with 50 to 100 mg by mouth in mild disease. ^[8]
• Folate. 1 to 5 mg orally daily until the anaemia improves, then 400 mcg daily if the cause persists; check and replete B12 first. In pregnancy use 400 to 800 mcg daily, and 4 mg daily when there is a high risk of neural tube defects. ^[6][8]
• Vitamin B12. 1000 micrograms intramuscularly three times weekly for 2 weeks, then weekly for one month, then monthly; or 1000 to 2000 micrograms orally daily when the gut is intact and symptoms mild. If pernicious anaemia, gastrectomy or complete ileal resection is present, use lifelong intramuscular or, when oral replacement is used in malabsorption, at least 1 mg daily. ^[2][6]
• Vitamin A. Use the World Health Organization age-specific dosing: 50,000 IU under 6 months, 100,000 IU at 6 to 12 months, and 200,000 IU over 12 months on days 1, 2 and 14 for xerophthalmia. For adults with deficiency, 100,000 IU daily for 3 days then 50,000 IU daily for 2 weeks is a commonly used curative regimen. Pregnant women at risk should receive no more than 10,000 IU daily or 25,000 IU weekly for 12 weeks because of fetotoxicity. Post-bariatric patients usually need around 10,000 IU daily, sometimes up to 100,000 IU daily, with monitoring. ^[3][4]
• Vitamin D. Curative cholecalciferol 3000 to 10,000 IU daily (average 5000 IU daily) for 1 to 2 months, or a single dose of 60,000 to 150,000 IU followed by 2000 IU daily maintenance. Prevention: about 400 IU daily between 51 and 70 years, and 600 to 1000 IU daily in older adults or with insufficient sun. ^[3]
• Vitamin E. 50 to 2000 IU daily. ^[3]
• Vitamin K. Replacement is largely limited to newborns and to overdose with anticoagulants; bleeding emergencies are treated with phytonadione. ^[3]
• Zinc. 30 to 45 mg daily is sufficient for deficiency, given 2 hours apart from iron; very high doses risk copper deficiency. ^[8]
• Iron. One tablet daily of ferrous sulphate, fumarate or gluconate; if not tolerated, one tablet every other day, alternative preparations, or intravenous iron. Continue for about 3 months after haemoglobin normalises, up to 6 months to replenish stores. After bariatric surgery, ferrous sulphate 200 mg daily (or ferrous fumarate 210 mg), twice daily in menstruating women. ^[9][11]

Refeeding syndrome is a potentially fatal condition that can complicate any re-introduction of nutrition to a malnourished patient, by the oral, enteral or parenteral route. It is driven by insulin surging as carbohydrate is given: phosphate, potassium, magnesium and thiamine move into cells, serum levels fall, and fluid and sodium are retained. ^[1]

Risk factors (UK National Institute for Health and Care Excellence criteria quoted in the review) are:

• Major (one of): body mass index under 16 kg per square metre; unintentional weight loss more than 15 per cent over 3 to 6 months; little or no nutritional intake for more than 10 days; low phosphate, potassium or magnesium before feeding. ^[1]
• Moderate (two of): body mass index under 18.5 kg per square metre; weight loss more than 10 per cent over 3 to 6 months; little or no intake for more than 5 days; a history of alcohol abuse, or drugs including insulin, chemotherapy, antacids or diuretics. ^[1]

Prevention and management:

1. Begin at 10 to 20 kcal per kilogram per day, given as roughly half carbohydrate and half fat (lipid). ^[1]
2. Correct thiamine first (200 to 300 mg daily by mouth) and give a balanced multivitamin. ^[1]
3. Check and replace phosphate, potassium and magnesium before and during feeding, and monitor every 12 hours for the first 3 days in high-risk patients. ^[1]
4. Replace fluids cautiously; watch for oedema, tachycardia and heart failure. Give phosphate intravenously when levels are under 0.6 mmol per litre. ^[1]
5. Increase the feeding rate at least daily, aiming to reach full needs within 5 to 7 days. ^[1]
6. If severe or life-threatening falls occur, reduce or pause calories and correct electrolytes, and consider escalation to intensive care. ^[1]

Malabsorption of fat-soluble vitamins follows any disturbance of fat digestion or absorption: coeliac or Crohn's disease, chronic pancreatitis, cholestasis, and ileal disease or resection (including short bowel). Fat-soluble vitamins (A, D, E, K) are affected first, and water-soluble losses add B1, B12, folate, copper and zinc. ^[3][9]

After bariatric surgery (especially Roux-en-Y gastric bypass and biliopancreatic diversion), deficiency is common and can be early and severe:

• Thiamine: 100 mg daily when intake is poor or there is vomiting; 200 to 300 mg daily, and urgent parenteral treatment, if deficiency is critical. Routine multivitamins should include 12 to 50 mg twice daily. ^[9]
• B12: intramuscular 1 mg every 3 months (more often if neurological symptoms are present). ^[9]
• Iron: 200 mg ferrous sulphate daily, or ferrous fumarate 210 mg, twice daily in menstruating women. ^[9]
• Vitamin A: 10,000 IU daily, and up to 50,000 IU daily in hypoabsorptive procedures, with monitoring; some patients need up to 100,000 IU daily. ^[9]
• Vitamin D and calcium: 800 mg calcium with 20 micrograms (800 IU) vitamin D (for example as Adcal D3), often requiring more. ^[9]
• Zinc and copper: maintain a zinc to copper ratio of 8 to 15 to 1; give 15 to 30 mg zinc and 2 mg copper daily. ^[9]
• Vitamin K: about 300 micrograms daily in biliopancreatic diversion. ^[9]
• Vitamin E: about 60 IU daily in some recommendations. ^[9]
• Selenium: replacement is recommended in all bariatric patients, with monitoring. ^[9]

Monitoring after bariatric surgery is performed at 1, 3, 6 and 12 months and then twice yearly, with parenteral replacement for severe deficiencies. Gastric surgery patients with prolonged vomiting or neurological symptoms require immediate high-dose parenteral thiamine (500 mg intravenously three times daily) together with other B vitamins and vitamin C. ^[9]

Vitamin deficiency remains a large global problem that modern diets alone do not solve.

• Around 250 million children worldwide are vitamin A deficient, leaving them vulnerable to night blindness, infection and death. ^[3]
• Iron deficiency is one of the most common causes of anaemia and of years lived with disability worldwide. ^[11]
• Iodine deficiency was historically the commonest preventable cause of brain damage. Universal salt iodisation now reaches about 88 per cent of the global population, 124 countries have mandatory salt iodisation laws, and the number of iodine-deficient countries fell from 113 in 1993 to 19 in 2019. Iodised salt is considered adequately fortified at 15 to 40 parts per million of iodine. ^[10]
• In 2019 there were roughly 180 million prevalent cases of iodine deficiency worldwide, concentrated in low- and middle-income regions. ^[10]
• Vitamin D deficiency is common even in industrialised countries in people with little sun exposure, older adults, dark-skinned or obese patients and those with malabsorption. ^[3]

Prevention programmes that have shown benefit:

• Vitamin A supplementation: 100,000 IU for infants aged 6 to 11 months and 200,000 IU every 4 to 6 months up to 5 years of age in communities where deficiency is a public health problem (prevalence of low serum retinol at least 20 per cent); plus access to vitamin A-rich foods, fortification and measles dosing. ^[4]
• Iodine: universal salt iodisation programmes (national or voluntary), which are regarded as one of public health's most cost-effective interventions. ^[10]
• Folate: folic acid fortification of staple foods has sharply reduced neural tube defects; women of childbearing age should take at least 0.4 mg daily, and those at high risk 4 mg daily. ^[6]
• Refeeding and malnutrition in emergencies: World Health Organization guidelines for inpatient treatment of severe malnutrition, with careful electrolyte replacement. ^[1]
• Bariatric and gastrointestinal follow-up: routine multivitamin and mineral supplementation with scheduled monitoring. ^[9]

• Children. Rickets (vitamin D), xerophthalmia (vitamin A), iron-deficiency anaemia and iodine-deficiency disorders still occur, particularly in resource-poor settings. ^[4][10]
• Pregnancy and breastfeeding. Folate 400 to 800 micrograms daily, with 4 mg in high-risk pregnancies; iron-deficiency is fought throughout pregnancy; iodine requirement rises. High-dose vitamin A is teratogenic, so pregnancy dosing must be restricted. ^[4][6][11]
• Older adults. Up to 30 per cent may be B12 deficient; malnutrition in isolation and dementia is frequent. ^[6][8]
• Renal failure and dialysis. Water-soluble vitamins (B1, B6, C, folate, zinc) are lost; replacement is often prescribed, although the evidence base varies. ^[8]
• Alcohol use disorder. Thiamine is frequently deficient and vitamin C deficiency is reported in about 80 per cent of patients; give both, plus magnesium and phosphate. ^[6][8]
• Critical illness. Thiamine and vitamin C depletion occur; trials of high-dose vitamin C in sepsis have not shown clear benefit. ^[8]

Refer or admit when there is:

• coma, confusion or ataxia suggesting Wernicke-Korsakoff syndrome;
• severe or bleeding scurvy;
• refeeding syndrome with life-threatening electrolyte falls;
• post-bariatric vomiting and neurological symptoms;
• megaloblastic anaemia with neurological signs, or very low B12 with poor response to oral treatment;
• xerophthalmia, keratomalacia or corneal ulceration;
• iron-deficiency anaemia with suspected gastrointestinal malignancy (fast-track referral);
• any suspected deficiency that does not improve after appropriate repletion.

• Thiamine, folate, iron and vitamin A are all inexpensive and available as oral or injectable preparations; avoid expensive proprietary combinations where simpler ones exist.
• Clinical diagnosis (diet plus a compatible syndrome plus response to treatment) is usually enough and spares testing costs; therapeutic trials are legitimate when the presentation is typical. ^[4][7]
• Universal salt iodisation and routine vitamin A supplementation campaigns reach the poorest households; support these programmes.
• In the absence of cardiopulmonary bypass and advanced imaging, the diagnostic work-up is clinical history, examination and a basic blood count plus, where available, ferritin or retinol.
• Start thiamine parenterally before giving intravenous glucose in any malnourished patient.

Deficiency topics that this page links to conceptually: anaemia (anaemia approach and iron deficiency), megaloblastic anaemia, Wernicke-Korsakoff syndrome, beriberi, pellagra, scurvy, rickets, osteomalacia, malnutrition, obesity and bariatric surgery, alcohol use disorder, refeeding syndrome. These are listed as plain text because links are added once the target topics are verified.

References are listed in the front matter of this page and are cited in the text with Ref n markers; there is no separate reference list in the body.