Should I continue monthly B12 (Vitamin B12) injections in a patient with schizophrenia whose B12 levels only increased to 500 pg/mL after a month of weekly injections?

Management of Vitamin B12 Supplementation in Schizophrenia with Borderline B12 Levels

Yes, you should continue monthly B12 injections for this patient with schizophrenia whose levels only increased to 500 pg/mL after weekly injections, as ongoing supplementation is necessary to maintain symptom improvement and prevent relapse.

Assessment of Current Situation

• Your patient has demonstrated clinical improvement in schizophrenia symptoms (resolution of hallucinations) after weekly B12 injections for one month
• The B12 level has increased but only to 500 pg/mL, which is adequate but not optimal
• You are awaiting intrinsic factor antibody results which will help determine if pernicious anemia is the underlying cause

Rationale for Continued Supplementation

• Vitamin B12 deficiency has been associated with psychiatric symptoms including psychosis 1
• The FDA label for cyanocobalamin indicates that patients with B12 deficiency require ongoing supplementation to prevent recurrence of symptoms and potential irreversible neurological damage 2
• Patients with pernicious anemia specifically require monthly injections for life 2

Recommended Treatment Plan

1. Continue B12 supplementation with monthly intramuscular injections of 1000 μg

   • This is the standard maintenance dose after initial loading 3, 4
   • Monthly administration is appropriate for maintenance therapy 3

2. Monitor B12 levels and clinical response

   • Check B12 levels at 3 months and then periodically (every 6-12 months)
   • Continue to assess psychiatric symptoms
   • Consider checking methylmalonic acid (MMA) and homocysteine levels if there's concern about functional B12 deficiency despite normal serum levels 3

3. Adjust treatment based on intrinsic factor antibody results

   • If positive: Continue lifelong monthly B12 injections as this indicates pernicious anemia 2
   • If negative: Continue monthly injections but consider investigating other causes of B12 malabsorption

Evidence Supporting B12 in Schizophrenia

• Research has demonstrated that vitamin B12 deficiency can present with psychiatric symptoms including psychosis without anemia 1
• A randomized controlled trial showed that folate plus vitamin B12 supplementation improved negative symptoms of schizophrenia 5
• Elevated homocysteine levels (which can result from B12 deficiency) have been associated with schizophrenia in male patients 6

Important Considerations

• Duration of treatment: For patients with documented B12 deficiency causing neuropsychiatric symptoms, long-term supplementation is typically required 3, 2
• Potential risks of discontinuation: Stopping B12 supplementation prematurely could lead to symptom recurrence and potentially irreversible neurological damage 2
• Monitoring: Regular assessment of both B12 levels and psychiatric symptoms is essential 3

Potential Pitfalls to Avoid

• Don't rely solely on serum B12 levels: Some patients may have functional B12 deficiency despite normal serum levels 3
• Don't discontinue treatment prematurely: The FDA label warns that failure to continue B12 supplementation can result in return of symptoms and potentially irreversible neurological damage 2
• Don't overlook the need for individualized dosing: According to recent research, up to 50% of individuals with B12 deficiency require individualized injection regimens with more frequent administration to remain symptom-free 7

The clinical improvement in your patient's hallucinations strongly suggests a relationship between B12 supplementation and symptom control, making continued monthly injections a prudent approach to maintain this improvement.