Treatment of Vitamin B12 Deficiency with Injections
For patients with confirmed vitamin B12 deficiency, the recommended treatment is 1000 μg of vitamin B12 administered intramuscularly, with an initial loading phase of three times weekly for 2 weeks, followed by monthly maintenance injections for life. 1, 2
Initial Treatment Protocol
- For patients with neurological symptoms: Administer 1000 μg of vitamin B12 intramuscularly on alternate days until symptoms improve, then transition to maintenance therapy 1, 2
- For patients without neurological symptoms: Administer 1000 μg intramuscularly three times weekly for 2 weeks as loading dose 1, 2
- The preferred formulations are methylcobalamin or hydroxycobalamin rather than cyanocobalamin, especially in patients with renal dysfunction 3, 1
Maintenance Therapy
- After the loading phase, continue with 1000 μg intramuscularly every month indefinitely 1, 2
- Monthly administration is more effective than the previously recommended 3-monthly injections in preventing clinical manifestations of deficiency 3, 1
- For patients with ileal resection of more than 20 cm, monthly prophylactic injections of 1000 μg are mandatory for life 3, 2
Special Considerations
- Patients with ileal Crohn's disease involving more than 30-60 cm are at risk for B12 deficiency even without resection and should be monitored closely 3
- Elderly patients have a higher prevalence of vitamin B12 deficiency, with metabolic B12 deficiency reaching 18.1% in patients over 80 years 3, 1
- Diagnosis of biochemical B12 deficiency is based on low serum cobalamin levels (<148 pM) along with elevated homocysteine (>15 mM) or methylmalonic acid (>270 mM) 3
Alternative Oral Supplementation
- High-dose oral vitamin B12 (1000-2000 μg daily) may be considered as an alternative to injections in selected patients without malabsorption issues 1, 4
- However, studies indicate that the effective oral dose needed to normalize B12 deficiency is 647-1032 μg daily, which is more than 200 times the recommended dietary allowance 5
- Parenteral administration remains the standard of care, particularly for patients with malabsorption conditions 3, 6
Administration Technique
- Standard injection kits include 1000 μg/mL cyanocobalamin, syringes, and needles for proper administration 7
- Use a 22G needle for drawing up the medication and a finer 30G needle for administration to minimize discomfort 7
Monitoring
- All patients with vitamin B12 deficiency should be monitored for clinical response 6
- Patients with ileal involvement or resection should be screened yearly for B12 deficiency 3
- Titration of injection frequency based solely on serum B12 levels is not recommended; clinical response should guide treatment 6