Metformin Link to Vitamin B12 Deficiency, Neuropathy in Diabetes

by: Miriam E Tucker
STOCKHOLM — Metformin-related vitamin B12 deficiency might contribute to clinically significant peripheral neuropathy in diabetes patients, new research suggests.
Guidelines from European Association for the Study of Diabetes (EASD) and the American Diabetes Association do mention vitamin B12 deficiency as a risk of metformin treatment for type 2 diabetes, but they don’t make recommendations for screening or supplementation, said Mattijs Out, MD, an internist of vascular medicine at Bethesda Diabetes Research Center, Hoogeveen, the Netherlands, who presented the findings last week at the European Association for the Study of Diabetes 2015 Meeting.
“This is important. The consequences of vitamin B12 deficiency, like neuropathy or mental changes, may be profound. Even more, they may be difficult to diagnose, because they may be ascribed to old age or diabetes itself and may be or become irreversible. On the other hand, vitamin B12 deficiency is relatively easy to diagnose, and treatment is easy, cheap, and effective,” Dr Out commented.
Previous research from Dr Out’s group and others has linked metformin use to vitamin B12 deficiency (<150 pmol/L), raising concern that the drug may be contributing to peripheral neuropathy separate from the effect of the diabetes itself.
In the current study, Dr Out and colleagues examined, for the first time, a very specific biomarker for tissue B12 deficiency, methylmalonic acid (MMA), and examinedthe impact of that on a validated neuropathy score; they found that the overall increase in MMA outweighed the benefit derived from metformin’s glucose-lowering effect.
But during the question-and-answer period, some doctors expressed skepticism, stating that they hadn’t seen very high rates of vitamin B12 deficiency in decades of metformin use.
Session moderator Guntram Schernthaner, MD, professor of medicine at the Medical University of Vienna, Austria, told Medscape Medical News, “I measure only in suspected cases and have almost never found a relationship.…The data aren’t strong enough in my opinion. I recommend a large database study to investigate how often it’s occurring.”
Dr Schernthaner added, “You can measure [vitamin B12] if you suspect [deficiency], but the key question is whether you should have routine screening. But before you recommend this, you have to prove it’s a true effect.”…….
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Source: Medscape