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BASICS

  • Vitamins are essential for normal metabolism and development.
  • Deficiency often seen in elderly, pregnant women, breastfed infants, malnourished, and chronic disease states.
  • Fat-soluble vitamins (A, D, E, K) have risk of toxicity; water-soluble rarely toxic.
  • True incidence of vitamin deficiencies varies by population and geography.

ETIOLOGY AND PATHOPHYSIOLOGY

  • Causes include decreased intake, malabsorption, increased demand (e.g., pregnancy, illness), or increased excretion.
  • Malabsorptive disorders: celiac disease, Crohn's, short bowel syndrome.
  • Drug-induced deficiencies: methotrexate, phenobarbital, metformin, H2 blockers, etc.
  • Bariatric surgery patients at high risk and require lifelong supplementation.
  • Genetic disorders: cystic fibrosis, Hartnup disease, transcobalamin II deficiency.

RISK FACTORS

  • Poverty, malnutrition, chronic alcohol use.
  • Chronic illnesses and malabsorptive states.
  • Dietary restrictions or fad diets.
  • Advanced age.
  • Exclusive breastfeeding without supplementation.

GENERAL PREVENTION

  • Avoid excessive vitamin supplementation to prevent toxicity.
  • Avoid restrictive diets; maintain balanced nutrition.
  • USPSTF recommendations:
  • Against low-dose vitamin D (<400 IU) and calcium (<1000 mg) for fracture prevention in community-dwelling adults.
  • Folic acid supplementation (0.4-0.8 mg daily) for women planning pregnancy to prevent neural tube defects.

COMMONLY ASSOCIATED CONDITIONS

  • Anemia, neuropathies, dermatitis, visual disturbances.
  • Vitamin A deficiency: night blindness.
  • Vitamin B1 deficiency: Wernicke encephalopathy, beriberi.
  • Vitamin B12 deficiency: pernicious anemia, neuropathy.
  • Vitamin C deficiency: scurvy.
  • Vitamin D deficiency: rickets, osteomalacia.

DIAGNOSIS

History

  • Assess dietary intake, supplement use.
  • Symptoms: neuropathy, visual changes, skin changes, bruising, poor wound healing, fractures.
  • Past medical and surgical history, including GI surgery.
  • Medication review for drugs causing deficiency.

Physical Exam

  • Neurologic exam: gait, cognitive impairment, neuropathy.
  • Skin exam: dermatitis, petechiae, ecchymoses.
  • Oral exam: glossitis, stomatitis.

Differential Diagnosis

  • Diabetes, thyroid disorders, multiple sclerosis, hematologic malignancies.

Tests

  • 25-OH vitamin D level.
  • Vitamin B12, folate levels.
  • Homocysteine and methylmalonic acid for B12 deficiency.
  • CBC, liver, kidney function.
  • Parathyroid hormone, calcium, phosphorus, magnesium.
  • No routine screening; test if symptomatic or high risk.

TREATMENT

  • Review all supplements and medications for interactions.
  • Treat deficiencies with appropriate vitamin replacement.
  • Vitamin D supplementation:
  • 600 IU/day for children >12 months and adults up to 70 years.
  • 800 IU/day for adults >71 years.
  • Vitamin B12 deficiency:
  • IM cyanocobalamin 1000 µg daily × 2 weeks, then maintenance dosing.
  • Oral high-dose therapy if no malabsorption.
  • Consider dietary consult for malnourished patients.
  • Bariatric surgery patients require lifelong supplementation.

PEDIATRIC AND PREGNANCY CONSIDERATIONS

  • Vitamin K deficiency common in neonates; prophylaxis with IM vitamin K at birth prevents hemorrhagic disease.
  • Vitamin D supplementation (400 IU/day) recommended for all breastfed infants starting soon after birth.
  • Pregnant women advised multivitamin with folic acid to prevent neural tube defects.

ONGOING CARE

  • Encourage balanced diet; limit unnecessary supplements.
  • Monitor for adverse effects or toxicities from fat-soluble vitamins.
  • Patient education on supplement use and drug interactions.

PROGNOSIS

  • Most vitamin deficiencies improve with supplementation.
  • Complications include toxicity (liver failure, neuropathy, kidney stones, hypercoagulability) if overdosed.
  • Untreated deficiency can cause irreversible neurological and hematological damage.

COMPLICATIONS

  • Vitamin A toxicity: skin desquamation.
  • Vitamin B6 toxicity: neuropathy.
  • Vitamin C and D: kidney stones.
  • Vitamin K: hypercoagulability.
  • Folic acid may mask B12 deficiency.

REFERENCES

  1. Langan RC, Goodbred AJ. Vitamin B12 deficiency: recognition and management. Am Fam Physician. 2017;96(6):384-389.
  2. Bibbins-Domingo K, Grossman DC, Curry SJ, et al; US Preventive Services Task Force. Folic acid supplementation for the prevention of neural tube defects: USPSTF recommendation statement. JAMA. 2017;317(2):183-189.
  3. Giustina A, Adler RA, Binkley N, et al. Controversies in vitamin D: summary statement from an international conference. J Clin Endocrinol Metab. 2019;104(2):234-240.

ICD10

  • E56.9 Vitamin deficiency, unspecified
  • E56.0 Vitamin D deficiency
  • E55.9 Vitamin D deficiency, unspecified

Clinical Pearls

  • Routine screening for vitamin D deficiency is not recommended unless symptoms or risk factors are present.
  • Vitamin D supplementation of 400 IU/day is recommended for all infants.
  • Excessive vitamin supplementation can cause toxicity, especially with fat-soluble vitamins.
  • Pregnant women should take daily folic acid supplementation to reduce neural tube defect risk.