Treatment of Vitamin B12 (Cobalamin) Deficiency
For vitamin B12 deficiency, treatment should be initiated immediately with hydroxocobalamin 1 mg intramuscularly, with frequency determined by the presence of neurological symptoms. 1, 2
Initial Treatment Protocol
With Neurological Involvement
- Administer hydroxocobalamin 1 mg intramuscularly on alternate days until no further improvement is observed 1, 2
- After improvement plateaus, transition to maintenance therapy with hydroxocobalamin 1 mg intramuscularly every 2 months 1, 2
- Seek urgent specialist advice from a neurologist and haematologist for patients with unexplained sensory, motor, or gait symptoms 1
Without Neurological Involvement
- Administer hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks 1, 2
- Follow with maintenance treatment of 1 mg intramuscularly every 2-3 months for life 1, 2
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, 3
- Vitamin B12 deficiency left untreated for longer than 3 months may produce permanent degenerative lesions of the spinal cord 3, 4
- Patients should be informed that if they have malabsorption issues, they will require lifelong injections 3, 4
Special Considerations
Monitoring
- During initial treatment, monitor serum potassium closely for the first 48 hours and replace if necessary 3
- Obtain hematocrit, reticulocyte count, vitamin B12, folate, and iron levels prior to treatment 3
- Repeat hematocrit and reticulocyte counts daily from the fifth to seventh days of therapy and then frequently until the hematocrit normalizes 3
Specific Patient Populations
- Post-bariatric surgery patients often require regular vitamin B12 injections due to malabsorption 1, 2
- Patients with more than 20 cm of distal ileum resected should receive prophylactic vitamin B12 injections (1000 μg) monthly for life 2
- Elderly patients have a higher risk of B12 deficiency, with metabolic B12 deficiency present in 18.1% of patients over 80 years 2, 5
Choice of Vitamin B12 Form
- Hydroxocobalamin is generally preferred for intramuscular administration 2, 6
- Methylcobalamin or hydroxocobalamin may be preferable to cyanocobalamin in patients with renal dysfunction 2
Long-term Management
- Treatment should continue until the reason for deficiency is corrected, or indefinitely if the cause cannot be reversed 2, 4
- According to recent expert consensus, up to 50% of individuals with malabsorption may require more frequent administration than standard guidelines suggest, ranging from daily or twice weekly to every 2-4 weeks, to remain symptom-free 4, 7
- Clinical symptoms should receive high priority in guiding treatment adjustments 7
Causes of B12 Deficiency to Address
- Dietary deficiency (vegetarians, vegans, malnourished individuals) 5
- Malabsorption (pernicious anemia, gastrointestinal pathology, atrophic gastritis) 3
- Medication-induced (antacids, metformin) 5
- Post-surgical (gastrectomy, bariatric surgery) 1, 3
By promptly diagnosing and treating vitamin B12 deficiency according to these guidelines, irreversible neurological damage can be prevented and optimal patient outcomes achieved.