What is the recommended supplementation regimen for patients at risk of Vitamin B12 deficiency?

Vitamin B12 Supplementation Regimen for At-Risk Patients

Patients at risk of Vitamin B12 deficiency should receive 1000 mcg (1 mg) of vitamin B12 intramuscularly monthly for life, with initial loading doses of 1000 mcg every other day for one week in those with confirmed deficiency. 1, 2, 3

Identifying At-Risk Populations

• Patients with more than 20 cm of distal ileum resected require prophylactic vitamin B12 supplementation at 1000 mcg monthly for life 4, 3
• Patients with pernicious anemia require lifelong parenteral B12 supplementation, as oral forms are not dependable 5, 6
• Patients on certain medications such as metformin, proton pump inhibitors, or histamine H2 blockers for extended periods should be monitored for B12 deficiency 7, 8
• Patients with Crohn's disease involving 30-60 cm of ileum are at risk even without resection and should be screened yearly 4, 3
• Elderly patients (>75 years) have higher risk of B12 deficiency, with prevalence reaching 18.1% in those over 80 years 2, 8
• Vegans or strict vegetarians require regular B12 supplementation 7, 8
• Patients who have undergone bariatric surgery require 1000 mcg daily oral supplementation or regular injections 2, 7

Dosing Protocols Based on Clinical Scenario

For Patients with Confirmed B12 Deficiency with Neurological Symptoms:

• Initial treatment: 1000 mcg intramuscularly on alternate days until no further improvement 2
• Maintenance: 1000 mcg intramuscularly every 2 months 2

For Patients with Confirmed B12 Deficiency without Neurological Symptoms:

• Initial treatment: 1000 mcg intramuscularly three times a week for 2 weeks 2, 3
• Maintenance: 1000 mcg intramuscularly every 2-3 months lifelong 2

For Prophylaxis in High-Risk Patients:

• Patients with ileal resection >20 cm: 1000 mcg intramuscularly monthly for life 4, 3
• Post-bariatric surgery: 1000 mcg intramuscularly every 3 months or 1000 mcg daily orally 2
• Patients on medications affecting B12 absorption: 1000-2000 mcg oral supplementation daily 1, 7

Route of Administration Considerations

• Intramuscular (IM) administration is the gold standard for patients with malabsorption issues 2, 3
• High-dose oral supplementation (1000-2000 mcg daily) may be effective for patients with normal intestinal absorption 6, 7
• Oral therapy (1200-2400 mcg daily) may be effective in treating B12 deficiency in some patients, but parenteral supplementation remains the reference standard for those with malabsorption 4, 9

Monitoring Recommendations

• Check serum B12 levels and homocysteine every 3 months until stabilization, then once yearly 2
• Target homocysteine level should be <10 μmol/L for optimal results 2
• CD patients with ileal involvement/resection should be screened yearly for B12 deficiency 4, 3

Important Cautions and Pitfalls

• Never administer folic acid before checking vitamin B12 status, as it can mask B12 deficiency and precipitate neurological complications 1, 2
• Do not discontinue B12 supplementation even if levels normalize in patients with permanent malabsorption issues 2, 9
• Avoid intravenous administration of cyanocobalamin as most of the vitamin will be lost in the urine 5, 6
• For patients with renal dysfunction, methylcobalamin or hydroxocobalamin may be preferable to cyanocobalamin 1, 2

Special Considerations

• Patients treated with sulphasalazine and methotrexate should also receive vitamin B9/folic acid supplementation 4
• For patients with thrombocytopenia requiring B12 supplementation, use smaller gauge needles (25-27G) and apply prolonged pressure at the injection site 2