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Diabetes Health Center

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Metformin Linked to B12 Deficiency

Peripheral Neuropathy Patients Who Take Diabetes Drug May Have Vitamin B12 Deficiency
WebMD Health News
Reviewed by Louise Chang, MD

June 8, 2009 -- The popular diabetes drug metformin may contribute to vitamin B12 deficiency, according to a new study.

Researchers found that 40% of type 2 diabetes patients using metformin had vitamin B12 deficiency or were in the low-normal range for the essential vitamin. And 77% of metformin users with vitamin B12 deficiency also had peripheral neuropathy, a common form of nerve damage associated with type 2 diabetes.

Peripheral neuropathy is a type of nerve damage most often characterized by pain, tingling, and numbness in the hands and feet.

Because peripheral neuropathy is such a major complication of diabetes, researchers say the results suggest that people using metformin be screened for vitamin B12 deficiency or supplemented with vitamin B12. Also, anyone already diagnosed with peripheral neuropathy who uses metformin should be screened for vitamin B12 deficiency.

Vitamin B12 is primarily found in meat and dairy products. In the body, it plays a critical role in making red blood cells and keeping the nervous system functioning properly. Symptoms of vitamin B12 deficiency include anemia (low red blood cell count), depression, or dementia; but often there are no symptoms if the vitamin levels are just a little low. B12 deficiency can lead to nerve symptoms similar to that of diabetic peripheral neuropathy, although the researchers note that they cannot be certain that B12 deficiency contributed to the peripheral neuropathy seen in their study.

Vitamin B12 Screening Urged for Metformin Users

The study, presented this week at the American Diabetes Association’s 69th Annual Scientific Sessions, looked at the prevalence of vitamin B12 deficiency in 76 people with type 2 diabetes who had been taking metformin for at least one year.

The results showed that more than three-fourths of metformin users who had low vitamin B12 levels also had evidence of peripheral neuropathy.

Researcher Mariejane Braza, of the University of Texas Health Science Center, and colleagues say that the number of people with peripheral neuropathy in the vitamin B12 deficiency group was surprising.

They say it’s not clear whether vitamin B12 deficiency may contribute to or cause peripheral neuropathy. But they recommend screening metformin users for vitamin B12 deficiency and supplementing the vitamin, when necessary, to reduce the risk of nerve damage.

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