One of the most commonly prescribed drugs for type 2 diabetes may lead to the development of vitamin B12 deficiency over time. Symptoms of the deficiency include fatigue, tingling or numbness in the feet or hands, mental confusion or forgetfulness and anemia. Some of these may be difficult to distinguish from possible consequences of the diabetes itself. The study was conducted in the Netherlands with nearly 400 patients. Half were given metformin three times daily for four years; the other half were treated with a placebo. Those taking metformin had vitamin B12 levels drop by about one-fifth. The patients on placebo had no significant change in levels of the vitamin. There is no medical consensus about regular screening for vitamin B12 levels in patients on metformin, so these patients may need to be pro-active and ask their doctors for a blood test. This might especially important for people also taking acid suppressing drugs like Aciphex, Nexium, Prevacid or Prilosec. Such medications may also make it harder to absorb vitamin B12. The combination could be a double whammy.
[British Medical Journal, May 19, 2010]