FRIDAY, May 21 (HealthDay News) -- Patients being treated with metformin to control their diabetes may have a higher risk of decreased levels of vitamin B-12 and increased homocysteine levels, according to research published in the May 20 online edition of the BMJ.
Jolien de Jager, M.D., of the Academic Medical Center in Amsterdam, the Netherlands, and colleagues randomized 390 patients with type 2 diabetes receiving insulin to either 850 mg metformin or placebo three times daily over 4.3 years.
The researchers found that metformin was significantly associated with a mean decrease of 19 percent in B-12 concentration and 5 percent in folate concentration, compared to placebo. However, after adjustment for body mass index and smoking, they found no significant effect of metformin on folate concentrations. The absolute risk of B-12 deficiency was 7.2 percentage points higher in the metformin group, the absolute risk of low B-12 was 11.2 percentage points higher in the metformin group, and the mean levels of homocysteine were inversely correlated with B-12 levels.
"Long-term treatment with metformin increases the risk of vitamin B-12 deficiency, which results in raised homocysteine concentrations. Vitamin B-12 deficiency is preventable; therefore, our findings suggest that regular measurement of vitamin B-12 concentrations during long-term metformin treatment should be strongly considered," the authors write.
The study was part of the Hyperinsulinaemia: the Outcome of its Metabolic Effects trial, which received grants from Altana, Lifescan, Merck Sante, Merck Sharp & Dohme and Novo Nordisk.
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