Recommended Dosage of Injectable Vitamin B12 (Cobalamin)
For vitamin B12 deficiency, the standard treatment is 1000 mcg administered intramuscularly every other day for one week, followed by monthly injections for maintenance therapy. 1
Initial Treatment Protocol for B12 Deficiency
- For severe deficiency or patients with neurological symptoms: 1000 mcg intramuscularly three times a week for 2 weeks 2
- Alternative loading regimen: 1000 mcg intramuscularly 5-6 times biweekly 3
- For neurological involvement specifically: 1000 mcg intramuscularly on alternate days until symptoms improve 2
Maintenance Therapy
- Standard maintenance: 1000 mcg intramuscularly once monthly 1, 3
- For patients with ongoing neurological symptoms: 1000 mcg every 2 months after improvement 2
- For patients with more than 20 cm of distal ileum resected: 1000 mcg monthly indefinitely 2, 1
Special Considerations
- Pregnant women after bariatric surgery should receive 1000 mcg every 3 months via intramuscular injection 2
- Pediatric dosing: For preterm and term infants up to 12 months on parenteral nutrition, 0.3 μg/kg/day; for older children, 1 μg/day 4
- Recent evidence suggests that up to 50% of patients may require individualized injection regimens with more frequent administration (ranging from daily or twice weekly to every 2-4 weeks) to remain symptom-free 5
Important Clinical Cautions
- Vitamin B12 deficiency left untreated for longer than 3 months may produce permanent degenerative lesions of the spinal cord 6
- Folic acid supplementation can mask vitamin B12 deficiency and should not be given before checking vitamin B12 status, as it may prevent anemia but allow progression of neurological damage 2, 6
- Monitoring during initial treatment should include serum potassium (first 48 hours), hematocrit, and reticulocyte counts 6
Alternative Administration Routes
- While intramuscular administration is traditionally preferred, especially for severe deficiency or neurological manifestations, high-dose oral supplementation (1000-2000 mcg daily) may be effective in many cases 1, 7, 8
- For patients without malabsorption issues, oral vitamin B12 at doses of 1000 μg daily has shown comparable effectiveness to intramuscular administration in normalizing serum B12 levels 8, 9
The choice between oral and intramuscular administration should consider the severity of deficiency, presence of neurological symptoms, and underlying cause of deficiency, with intramuscular administration being preferred for severe cases or those with malabsorption issues.