Treatment for Low Vitamin B Levels
For vitamin B12 deficiency, the recommended treatment is 1000-2000 μg oral vitamin B12 daily, which is equally effective as intramuscular administration for most patients, with better cost-effectiveness and patient acceptability. 1, 2
Diagnosis and Assessment
- Check vitamin B12 levels with either:
- Total B12 (serum cobalamin)
- Active B12 (serum holotranscobalamin)
- Interpretation of results 1:
- Confirmed deficiency: Total B12 <180 ng/L or active B12 <25 pmol/L
- Indeterminate: Total B12 180-350 ng/L or active B12 25-70 pmol/L
- Deficiency unlikely: Total B12 >350 ng/L or active B12 >70 pmol/L
- For indeterminate results, consider methylmalonic acid (MMA) testing
Treatment Protocol for Vitamin B12 Deficiency
Oral Supplementation (First-line for most patients)
- Dosage: 1000-2000 μg daily 1, 2, 3
- Duration: Continue until levels normalize (typically within 3 months), then maintenance therapy
- Maintenance: 250-350 μg daily or 1000 μg weekly 1
Intramuscular (IM) Supplementation (For specific cases)
- Indications:
- Pernicious anemia
- Severe malabsorption
- Neurological symptoms
- Compliance concerns
- Swallowing difficulties
- Initial dosage: 1000 μg IM daily for 6-7 days 4, 5
- Followed by: 1000 μg IM every other day for 7 doses, then every 3-4 days for 2-3 weeks
- Maintenance: 1000 μg IM monthly for life 4, 5
Special Populations and Considerations
Risk Factors Requiring Screening and Treatment 1
- Vegan/vegetarian diet
- Gastric or ileal resection
- Medications (metformin, proton pump inhibitors, colchicine)
- Malabsorption disorders
- Age >75 years
- Post-bariatric surgery
Post-Bariatric Surgery Patients
- Require 1000 μg oral B12 daily indefinitely 1
- For those with malabsorption: Consider IM route
Patients with Crohn's Disease
- Screen yearly for B12 deficiency
- If >20 cm of distal ileum is resected, administer 1000 μg of vitamin B12 monthly 1
Important Cautions
- Never administer folic acid before treating B12 deficiency, as this may mask hematologic manifestations while allowing neurological damage to progress 1
- For patients with pernicious anemia, parenteral vitamin B12 is required for life 4, 5
- High-quality evidence shows oral vitamin B12 is as effective as IM administration in normalizing serum levels, even in many malabsorption cases 2, 3
Monitoring and Follow-up
- Re-examine clinical symptoms and repeat vitamin B12 levels at 3 months to verify normalization 1
- For patients with ongoing risk factors, monitor vitamin B12 levels every 6-12 months 1
- If other vitamin deficiencies are present, they should be treated concurrently 4, 5
The evidence strongly supports that oral vitamin B12 supplementation is equally effective as IM administration for most patients, with better cost-effectiveness and fewer adverse events 2, 3. However, for patients with severe malabsorption or pernicious anemia, IM administration remains the standard of care 4, 5.