What is the recommended treatment for Vitamin B12 deficiency?

Treatment of Vitamin B12 Deficiency

For confirmed vitamin B12 deficiency, the recommended treatment is 1000 μg cyanocobalamin monthly via intramuscular injection, or 1000-2000 μg daily oral supplementation for those without malabsorption issues. 1

Diagnosis Approach

• Screening should include at least two biomarkers:
  • Serum B12 levels plus either holotranscobalamin (holo-TC) or methylmalonic acid (MMA) 1
  • Test for anti-intrinsic factor antibodies in patients with autoimmune diseases, glossitis, anemia, and neuropathy 1

Treatment Algorithm

1. Pernicious Anemia (with malabsorption)

• Intramuscular injection is mandatory 2
  • Initial loading: 100 mcg daily for 6-7 days via intramuscular injection 2
  • If clinical improvement occurs: 100 mcg on alternate days for 7 doses, then every 3-4 days for 2-3 weeks 2
  • Maintenance: 100 mcg monthly for life 2
  • Note: Many guidelines now recommend higher doses of 1000 μg for more effective treatment 1, 3

2. B12 Deficiency without Malabsorption

• Oral supplementation is effective 1, 4
  • 1000-2000 μg daily oral supplementation 1, 5
  • High-dose oral B12 (1000-2000 μg) achieves similar results to injections 4

3. Special Populations

• Vegans/vegetarians: 250-350 μg daily or 1000 μg weekly oral B12 1
• Post-bariatric surgery: 1000 μg oral B12 daily indefinitely 1
• Crohn's disease with ileal involvement: 1000 μg monthly if >20 cm of distal ileum is resected 1
• Breastfeeding mothers: at least 2.8 mg cyanocobalamin daily 1

Monitoring Protocol

• Check B12 levels at 3,6, and 12 months in the first year after starting supplementation 1
• Once levels stabilize, annual monitoring is sufficient for patients requiring lifelong supplementation 1
• More frequent monitoring for patients with ongoing risk factors (malabsorption disorders, bariatric surgery, etc.) 1

Important Clinical Considerations

Form of B12

• For neurological symptoms, methylcobalamin or hydroxocobalamin may be preferred over cyanocobalamin 1
• Avoid intravenous administration as most of the vitamin will be lost in urine 2

Medication Interactions

• Review medications that may impair B12 absorption:
  • Proton pump inhibitors (PPIs)
  • H2 receptor antagonists
  • Metformin (monitor B12 levels after 4+ years of use)
  • Colchicine, phenobarbital, pregabalin, primidone 1

Treatment Response

• Expect 35-51% decrease in homocysteine and 28-48% decrease in methylmalonic acid with appropriate treatment 1
• Complete resolution occurs in only about 14% of patients 1
• Better outcomes associated with:
  • Absence of sensory dermatomal deficit, Romberg sign, and Babinski sign
  • MRI lesions in ≤7 spinal segments
  • Age less than 50 years
  • Early diagnosis and treatment 1

Recent Evidence on Oral Treatment for Pernicious Anemia

• Recent research (2024) suggests that oral supplementation with 1000 μg/day of cyanocobalamin can effectively treat vitamin B12 deficiency even in pernicious anemia patients 6
• After one month of treatment, 88.5% of patients were no longer deficient, with improvements persisting throughout 12-month follow-up 6

Common Pitfalls to Avoid

• Don't rely on serum B12 levels alone for diagnosis; include methylmalonic acid or holotranscobalamin 1
• Don't stop treatment prematurely - many patients require lifelong supplementation 1, 2
• Don't use intravenous route for B12 administration (results in urinary loss) 2
• Don't overlook potential causes of B12 deficiency (medications, dietary restrictions, malabsorption) 1, 7
• Don't use inadequate dosing - research shows effective doses are 200+ times the recommended dietary allowance 1