Therapeutic Range for Vitamin B12 Injections
The standard therapeutic dosing for vitamin B12 injections is 1000 micrograms (1 mg) administered intramuscularly, with frequency ranging from every other day during initial loading to monthly for maintenance therapy in most cases of B12 deficiency. 1, 2
Initial Loading Dose Protocols
- For vitamin B12 deficiency with neurological involvement: Administer hydroxocobalamin 1 mg intramuscularly on alternate days until no further improvement is observed, then transition to maintenance therapy 1
- For vitamin B12 deficiency without neurological involvement: Initial treatment is hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks 1
- Standard treatment protocol: 1000 mcg of vitamin B12 administered intramuscularly every other day for one week 2
Maintenance Dose Protocols
- After initial loading, maintenance therapy consists of 1 mg intramuscularly every 2-3 months lifelong for patients without neurological involvement 1
- For patients with neurological involvement, maintenance consists of hydroxocobalamin 1 mg intramuscularly every 2 months 1, 3
- Monthly administration of 1000 mcg IM is more effective than 3-monthly injections for maintenance therapy 3
- For patients with more than 20 cm of distal ileum resected, prophylactic vitamin B12 injections (1000 μg) should be administered monthly for life 1, 2
Special Populations and Considerations
- For patients after bariatric surgery: Vitamin B12 supplementation at 1 mg every 3 months via intramuscular injection or 1 mg daily orally 1
- For pregnant women after bariatric surgery: Continue vitamin B12 supplementation at 1000 micrograms every 3 months via intramuscular injection or 1000 micrograms daily orally 3
- For preterm and term infants up to 12 months on parenteral nutrition: 0.3 μg/kg/day, and for older children, 1 μg/day 3
Individualized Treatment Needs
- Clinical experience suggests that up to 50% of individuals may require more frequent administration than standard protocols, ranging from daily or twice weekly to every 2-4 weeks, to remain symptom-free 4
- The British National Formulary guidelines suggest many individuals with B12 deficiency due to malabsorption can be managed with 1000 µg intramuscular hydroxocobalamin once every two months after the initial loading 4
Monitoring Recommendations
- Serum B12 and total homocysteine should be measured to assess vitamin B12 status, with a target homocysteine level of <10 μmol/L for optimal results 1
- In patients with deficiency, monitoring should occur every 3 months until stabilization, then once a year 1
- "Titration" of injection frequency based on measuring biomarkers such as serum B12 or methylmalonic acid is not recommended; instead, treatment should be based on clinical response 4
Important Cautions
- Never administer folic acid before treating vitamin B12 deficiency, as it may mask underlying B12 deficiency and precipitate subacute combined degeneration of the spinal cord 1
- For patients with thrombocytopenia requiring vitamin B12 supplementation, special precautions may be needed depending on platelet count severity 1
- Methylcobalamin or hydroxocobalamin may be preferable to cyanocobalamin in patients with renal dysfunction 1, 3