More evidence that metformin can cause vitamin B12 deficiency

Patients with advanced diabetes whose insulin receptors have sustained years of damaging insult sometimes require the medication metformin. Clinicians and patients alike need to bear in mind that metformin tends to cause a deficiency of the critical nutrient cofactor vitamin B12. Research just published in the British Medical Journal reminds us that this is not in question or a matter of opinion. The authors set out to...

"...study the effects of metformin on the incidence of vitamin B-12 deficiency (<150 pmol/l), low concentrations of vitamin B-12 (150-220 pmol/l), and folate and homocysteine concentrations in patients with type 2 diabetes receiving treatment with insulin."

Incidentally, this reference for vitamin B-12 is extremely low and far from optimal. After following 390 patients with type 2 diabetes who were treated with 850 mg metformin or placebo three times a day for 4.3 years, what did they conclude from their data?

"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."

Do remember that serum B12 is not a reliable indicator. To ascertain that your genetic and circumstantial needs for this critical cofactor are actually being methylmalonic acid, measured in serum or urine, is much more reliable.