Treatment of Vitamin B12 Deficiency
For vitamin B12 deficiency, the recommended treatment is intramuscular hydroxocobalamin 1 mg administered three times a week for 2 weeks for patients without neurological involvement, followed by lifelong maintenance therapy of 1 mg intramuscularly every 2-3 months. 1
Initial Treatment Algorithm Based on Clinical Presentation
For patients WITH neurological involvement:
- Administer hydroxocobalamin 1 mg intramuscularly on alternate days until no further improvement is seen
- Seek urgent specialist advice from a neurologist and haematologist
- Continue with maintenance dose of hydroxocobalamin 1 mg intramuscularly every 2 months 1
- Do NOT give folic acid first as it may mask B12 deficiency and precipitate subacute combined degeneration of the spinal cord
For patients WITHOUT neurological involvement:
- Administer hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks
- Follow with maintenance treatment of 1 mg intramuscularly every 2-3 months for life 1
Special Considerations
For patients with ileal resection:
- Patients with more than 20 cm of distal ileum resected require prophylactic vitamin B12 supplementation of 1000 mg intramuscularly every month indefinitely 1
For patients with pernicious anemia:
- Parenteral vitamin B12 is the recommended treatment and will be required for the remainder of the patient's life
- The oral form is not dependable in these patients 2, 3
Dosage Considerations
While the British guidelines recommend hydroxocobalamin 1 mg, some evidence suggests that higher doses (1000-2000 mcg) may be more effective for retention 4. The most recent evidence indicates that treatment should be individualized based on symptom response rather than serum levels alone 5.
Oral vs. Intramuscular Administration
Although some research suggests oral high-dose vitamin B12 (1000-2000 mcg daily) may be as effective as intramuscular administration 6, 7, the most authoritative guidelines still recommend the intramuscular route, particularly for:
- Patients with malabsorption issues
- Pernicious anemia
- Severe deficiency
- Neurological symptoms
Common Pitfalls to Avoid
- Never give folic acid before correcting B12 deficiency - this can mask B12 deficiency while neurological damage progresses
- Don't rely on oral therapy for patients with malabsorption or pernicious anemia
- Don't discontinue maintenance therapy - B12 deficiency treatment is typically lifelong, especially in cases of malabsorption or pernicious anemia
- Don't wait for complete neurological symptoms before initiating treatment - early intervention prevents irreversible neurological damage
- Don't use serum B12 or methylmalonic acid levels to titrate injection frequency - treatment should be based on clinical response 5
Monitoring
- Monitor clinical response to therapy
- For patients with neurological symptoms, continue treatment until no further improvement is seen
- Regular follow-up is essential to ensure adequate maintenance therapy