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MetabolicICD-10: E53.8Affects an estimated 6% of people under 60 and nearly 20% of those over 60 in the U.S.

Vitamin B12 Deficiency

Vitamin B12 deficiency occurs when the body lacks adequate cobalamin, a vitamin essential for red blood cell formation, neurological function, and DNA synthesis. The deficiency can result from insufficient dietary intake, malabsorption conditions, or autoimmune destruction of intrinsic factor (pernicious anemia). If left untreated, vitamin B12 deficiency can cause irreversible neurological damage and severe megaloblastic anemia.

Symptoms

Fatigue, weakness, and lightheadedness
Pale or jaundiced (yellowish) skin
Numbness and tingling in the hands and feet (peripheral neuropathy)
Difficulty walking and balance problems
Cognitive difficulties including memory loss and confusion
Glossitis (swollen, inflamed tongue) and mouth ulcers
Mood changes including depression and irritability
Shortness of breath and heart palpitations

Causes

  • Pernicious anemia (autoimmune destruction of intrinsic factor needed for B12 absorption)
  • Dietary insufficiency, particularly in strict vegans and vegetarians
  • Malabsorption from conditions like celiac disease, Crohn's disease, or atrophic gastritis
  • Chronic use of medications that reduce B12 absorption (metformin, proton pump inhibitors, H2 blockers)
  • Surgical removal of parts of the stomach or small intestine (gastric bypass, ileal resection)

Risk Factors

  • Strict vegan or vegetarian diet without supplementation
  • Age over 60 (decreased stomach acid and intrinsic factor production)
  • History of gastrointestinal surgery or disorders
  • Long-term use of metformin or acid-suppressing medications
  • Autoimmune conditions (type 1 diabetes, thyroid disease, vitiligo)
  • Heavy alcohol consumption

Diagnosis

  • Serum vitamin B12 level (low levels confirm deficiency)
  • Methylmalonic acid (MMA) and homocysteine levels (elevated in B12 deficiency)
  • Complete blood count (CBC) showing macrocytic anemia (large red blood cells)
  • Intrinsic factor antibodies and parietal cell antibodies to diagnose pernicious anemia
  • Peripheral blood smear showing hypersegmented neutrophils

Treatment

  • Intramuscular B12 (cyanocobalamin or hydroxocobalamin) injections for severe deficiency or malabsorption
  • High-dose oral B12 supplementation (1,000-2,000 mcg daily) for mild to moderate cases
  • Sublingual B12 tablets or nasal spray as alternative delivery methods
  • Dietary counseling to increase B12-rich food intake (meat, fish, eggs, dairy)
  • Treatment of underlying conditions causing malabsorption
  • Lifelong supplementation for pernicious anemia or permanent malabsorption

Prevention

  • Ensure adequate dietary intake of B12 through animal products or fortified foods
  • Take a B12 supplement if following a vegan or vegetarian diet
  • Have B12 levels checked regularly if over 60 or taking metformin or PPIs
  • Address gastrointestinal conditions that impair nutrient absorption

When to See a Doctor

  • You experience persistent fatigue with numbness or tingling in extremities
  • You notice difficulty walking, balance problems, or cognitive changes
  • You follow a vegan diet and have not been supplementing with B12

Frequently Asked Questions

Related Conditions

Anemia

Metabolic

Hypothyroidism

Endocrine

Depression

Mental Health

Type 2 Diabetes

Endocrine

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Medical Disclaimer: This content is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.

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