New Research Shows Long Term Metformin Use Lowers B12 Levels

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Drug textbooks and handbooks alike have long documented that Metformin use lowers vitamin B12 levels. Metformin is the most commonly prescribed medication for type II diabetics. It accounts for millions of prescriptions each year. Dr. Jill P. Crandall of the Albert Einstein College of Medicine in New York City analyzed the data of two large studies, the Diabetes Prevention Program and the Diabetes Prevention Program Outcomes Study, for the relationship of Metformin use and B12 levels. B12 values were measured in one group taking Metformin and another group taking a placebo. The author found that B12 levels were lower in the group taking Metformin as compared to the placebo group. The findings were published earlier this year in the Journal of Clinical Endocrinology & Metabolism.

It is of course no reason to discontinue Metformin as the threat of lowered B12 values pales in comparison to the harm diabetes causes. In fact, Metformin has many advantages over most pharmaceutical agents used to control blood sugar. One being that it sensitizes insulin. That means it makes your own insulin function better. Diabetics should however beware of the signs of B12 deficiency.

Vitamin B12 deficiency is known to cause fatigue and a certain type of anemia related to low B12 or folate levels. B12 deficiency is also known to cause neuropathy, a symptom of concern to diabetics. Diabetic neuropathy signifies the damaging effects of high blood sugar on the nerves. Neuropathy in diabetics manifests itself in the following symptoms: burning, tingling, numbness, pain, and pins and needles sensation. It usually affects the hands and feet. The symptom can become extremely painful and debilitating; even requiring medications to stop the nerve pain. We know that B12 can help treat both diabetic and B12 deficiency neuropathy. The issue brings to light a new question, could B12 deficiency be a catalyst for diabetic neuropathy?

Dr. Crandall did not draw that conclusion but did propose that patients undergoing long term Metformin therapy should have their B12 values measured. Since B12 is both innocuous and water soluble, another sensible approach would be to receive monthly or bimonthly injections of vitamin B12 or to take a supplemental B12 by mouth. However, irrespective of B12 status, blood sugar control is most important in preventing diabetic neuropathy.