Treatment for Vitamin B12 Deficiency
The recommended treatment for vitamin B12 deficiency 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, followed by maintenance treatment 1
- 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
- Monthly administration of 1000 mcg IM is more effective than 3-monthly injections for maintenance therapy 3
Treatment Based on Cause of Deficiency
- For pernicious anemia: Parenteral vitamin B12 is the recommended treatment and will be required for life 4
- 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: 1000 micrograms intramuscularly every 3 months or 1000 micrograms daily orally 2
Oral Supplementation Option
- High-dose oral vitamin B12 (1000-2000 mcg daily) may be considered after the initial IM loading phase if the patient has no neurological symptoms 3, 5
- Recent research shows oral supplementation with 1000 μg/day of cyanocobalamin can improve vitamin B12 deficiency even in pernicious anemia 6
- Oral administration of high-dose vitamin B12 (1-2 mg daily) has been shown to be as effective as intramuscular administration for correcting anemia and neurologic symptoms in many patients 5
Important Considerations and Monitoring
- Do not 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
- Use either total B12 or active B12 as the initial test, and consider measuring methylmalonic acid as a confirmatory test when initial results are indeterminate 1
- For 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
- For vegans or strict vegetarians: daily oral supplementation with 1000 mcg is recommended 5
- Patients on long-term metformin or proton pump inhibitors should be monitored for B12 deficiency 5
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, so treatment with a combination or hydroxocobalamin is ideal 7