What is the treatment for vitamin B12 deficiency?

Treatment for Vitamin B12 Deficiency

The standard treatment for vitamin B12 deficiency is 1000 μg vitamin B12 intramuscular injection every other day for one week, followed by 1000 μg monthly for life, though oral supplementation at 1000-2000 μg daily is equally effective for most patients. 1

Diagnosis Confirmation

Before initiating treatment, confirm the diagnosis with:

• Serum cobalamin levels (<148 pM)
• Functional biomarkers:
  • Homocysteine (>15 μM)
  • Methylmalonic acid (>270 μM) 1

Treatment Options

Intramuscular (IM) Administration

• Initial: 1000 μg every other day for one week
• Maintenance: 1000 μg monthly for life 1, 2
• Preferred for:
  • Severe deficiency
  • Severe neurological symptoms
  • Pernicious anemia
  • Malabsorption conditions 2

Oral Administration

• Dosage: 1000-2000 μg daily 1
• Equally effective as IM administration for most patients with confirmed B12 deficiency 1, 3
• More cost-effective than IM administration 3
• Appropriate for:
  • Most patients without severe malabsorption
  • Patients who prefer oral administration
  • Maintenance therapy 4

Special Populations

Specific Patient Groups Requiring Supplementation

1. Patients with ileal resection >20 cm:

   • Require lifelong supplementation
   • 1000 μg monthly 1

2. Vegans and vegetarians:

   • Daily: 250-350 μg OR
   • Weekly: 1000 μg 1

3. Post-bariatric surgery patients:

   • 1000 μg oral B12 daily indefinitely 1

4. Crohn's disease with ileal involvement/resection:

   • 1000 μg monthly if >20 cm of distal ileum is resected
   • Yearly screening for B12 deficiency 1

5. Elderly patients (>75 years):

   • Should consume fortified foods or supplements 4

Risk Factors to Consider

Common risk factors for B12 deficiency include:

• Vegan/vegetarian diet
• Gastric or ileal resection
• Medications (metformin, proton pump inhibitors, colchicine)
• Malabsorption disorders
• Age >75 years
• Pernicious anemia
• Gastrointestinal pathology or surgery 1, 5, 4

Monitoring and Follow-up

• Re-examine clinical symptoms 2-3 months after initiating treatment
• Repeat vitamin B12 levels at 3 months to verify normalization
• Monitor hematocrit and reticulocyte counts daily from days 5-7 of therapy until hematocrit normalizes
• Continue yearly screening for patients with ongoing risk factors 1, 2

Important Cautions

1. Avoid folic acid before treating B12 deficiency:

   • Folic acid may mask B12 deficiency while allowing neurological damage to progress
   • Keep total daily folate consumption below 1 mg unless specifically treating folate deficiency 1, 2

2. Urgency of treatment:

   • Vitamin B12 deficiency that progresses for longer than 3 months may produce permanent degenerative lesions of the spinal cord 2

3. Potassium monitoring:

   • During initial treatment of pernicious anemia, serum potassium must be closely observed for the first 48 hours and replaced if necessary 2

Treatment Algorithm

1. Confirm diagnosis with serum B12, homocysteine, and methylmalonic acid levels
2. Assess severity:
   • If severe neurological symptoms or severe deficiency: Begin with IM administration
   • If mild to moderate deficiency without severe symptoms: Oral or IM are both appropriate
3. Initiate treatment based on route selected:
   • IM: 1000 μg every other day for one week, then monthly
   • Oral: 1000-2000 μg daily
4. Monitor response at 3 months with repeat B12 levels
5. Continue maintenance therapy based on underlying cause