Treatment for Vitamin B12 Deficiency
For vitamin B12 deficiency, the recommended treatment is hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks, followed by maintenance treatment with 1 mg intramuscularly every 2-3 months for life. 1
Initial Treatment Based on Clinical Presentation
- For patients without neurological involvement: hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks, then maintenance with 1 mg intramuscularly every 2-3 months for life 1, 2
- For patients with neurological involvement: hydroxocobalamin 1 mg intramuscularly on alternate days until no further improvement, then transition to maintenance with 1 mg intramuscularly every 2 months 1, 2
- Cyanocobalamin can also be used at a dose of 1000 mcg daily for 6-7 days by intramuscular injection, followed by alternate day dosing for 7 doses, then every 3-4 days for 2-3 weeks, and finally 100 mcg monthly for life 3
Treatment Based on Cause of Deficiency
- For patients with malabsorption (including pernicious anemia): parenteral vitamin B12 is required for life 1, 3
- For patients with ileal resection (>20 cm of distal ileum): prophylactic vitamin B12 injections (1000 μg) monthly for life 1, 2
- For patients after bariatric surgery: vitamin B12 supplementation at 1 mg every 3 months via intramuscular injection or 1 mg daily orally 2
- For patients with normal intestinal absorption: oral supplementation may be sufficient after initial parenteral treatment 3, 4
Oral vs. Parenteral Administration
- Recent evidence suggests that high-dose oral vitamin B12 (1000-2000 mcg daily) may be effective even in pernicious anemia due to passive absorption 5
- A 2024 study showed that oral supplementation with 1000 μg/day of cyanocobalamin improved vitamin B12 deficiency in pernicious anemia patients 5
- However, for patients with severe deficiency, neurological symptoms, or malabsorption issues, parenteral administration remains the preferred initial treatment 1, 2
Important Considerations and Monitoring
- Never administer folic acid before treating vitamin B12 deficiency, as it may mask underlying deficiency and precipitate subacute combined degeneration of the spinal cord 1, 2
- Check both vitamin B12 and folate levels, as folate deficiency may coexist 1
- For monitoring, measure serum B12 and total homocysteine, with a target homocysteine level of <10 μmol/L 2
- In patients with deficiency, monitoring should occur every 3 months until stabilization, then once a year 2
Special Populations
- Elderly patients have a higher risk of B12 deficiency, with metabolic B12 deficiency present in 18.1% of patients over 80 years 1, 2
- For patients with thrombocytopenia requiring vitamin B12, intramuscular administration can be safely performed with platelet count >50 × 10⁹/L 1, 2
- For patients with severe thrombocytopenia (platelet count 25-50 × 10⁹/L), use smaller gauge needles (25-27G) for IM injection and apply prolonged pressure at the injection site 2
Type of Vitamin B12
- Hydroxocobalamin is generally preferred for intramuscular administration 1, 2
- Methylcobalamin or hydroxocobalamin may be preferable to cyanocobalamin in patients with renal dysfunction 2
- Both methylcobalamin and adenosylcobalamin are essential active forms with distinct metabolic functions 6
Remember that treatment should continue until the reason for deficiency is corrected, or indefinitely if the cause cannot be reversed 2. The treatment approach should be tailored based on the cause of deficiency and the presence of neurological symptoms.