What is the recommended treatment for Vitamin B12 deficiency?

Treatment of Vitamin B12 Deficiency

For vitamin B12 deficiency, the recommended treatment is 1,000-2,000 mcg of vitamin B12 daily, with the route of administration (oral vs. intramuscular) determined by the underlying cause and severity of the deficiency. 1

Diagnostic Approach

• Initial testing should include either total B12 (serum cobalamin) or active B12 (serum holotranscobalamin)
  • 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
  • Unlikely deficiency: Total B12 >350 ng/L or active B12 >70 pmol/L 1
• For indeterminate results, measure serum methylmalonic acid (MMA) to confirm deficiency
• A comprehensive evaluation should include MMA, homocysteine levels, complete blood count, and folate levels 1

Treatment Algorithm

1. Pernicious Anemia

• Intramuscular (IM) administration is the recommended treatment:
  • Initial dosing: 100 mcg daily for 6-7 days by IM injection
  • If clinical improvement occurs: 100 mcg on alternate days for 7 doses, then every 3-4 days for 2-3 weeks
  • Maintenance: 100 mcg monthly for life 2
• Alternative: Recent evidence suggests oral supplementation at 1,000 mcg daily can be effective even in pernicious anemia 3, though this contradicts traditional FDA guidance

2. Normal Intestinal Absorption (Dietary Deficiency)

• Oral vitamin B12 at 1,500-2,000 mcg daily for 3 months 1
• After correction, maintenance with oral supplements or dietary adjustment

3. Malabsorption (Non-Pernicious Causes)

• Oral administration of high-dose vitamin B12 (1,500 mcg daily) is as effective as IM administration for most patients, with 1-2% absorption via passive diffusion even in malabsorption 1
• For severe malabsorption or neurological symptoms, consider IM route initially

4. Severe Deficiency with Neurological Symptoms

• IM administration is preferred for rapid correction: 1,000 mcg daily for days 1-10
• Maintenance: 1,000 mcg IM monthly 1

Monitoring Response

• Assess response after 3 months by measuring serum B12 levels 1
• Monitor platelet count until normalization
• For neurological symptoms, clinical improvement may take 3-6 months

Special Considerations

High-Risk Populations Requiring Screening and Early Intervention

• Elderly patients (>75 years)
• Patients on metformin (>4 months)
• Patients on proton pump inhibitors (>12 months)
• Vegans or strict vegetarians
• Patients with malabsorption disorders
• Patients with gastric or small intestine resections 1

Route of Administration Considerations

• Sublingual B12 offers comparable efficacy to IM with better compliance and cost-effectiveness 1
• IM therapy leads to more rapid improvement and should be used in severe deficiency 4
• Oral therapy (1,000-2,000 mcg daily) is effective for most patients, even those with malabsorption 1

Maintenance Therapy

• For reversible causes: May not require long-term supplementation if the cause is addressed
• For irreversible causes (pernicious anemia, ileal resection): Lifelong supplementation required 1
• Post-bariatric surgery patients: 1 mg oral vitamin B12 daily indefinitely 4

Common Pitfalls to Avoid

1. Relying solely on serum B12 testing - This has limitations and should be combined with clinical assessment and additional markers like MMA 1
2. Inadequate treatment duration - Neurological damage may become permanent if treatment is delayed or inadequate 1
3. Using intravenous route - This will result in almost all vitamin being lost in urine 2
4. Failure to identify underlying cause - Treatment approach differs based on etiology
5. Inadequate monitoring - Some patients require individualized injection regimens with more frequent administration to remain symptom-free 5