What You Should Know about Metformin and B12

Metformin is one of the most commonly prescribed oral medications for type 2 diabetes. In fact, since Metformin is considered a first-line intervention, it is often the first medication prescribed for type 2 diabetes.

Several studies, however, have concluded that Metformin is associated with a higher prevalence of vitamin B12 deficiency. Read on to see what this might mean for you.

About Vitamin B12

Vitamin B12 is a water-soluble vitamin whose molecules happen to be attached, or bound, to proteins in foods. This means that B12 in our diet comes from those foods that contain protein: meat, fish, poultry, eggs, and milk and milk products. The Recommended Dietary Allowance (RDA) for vitamin B12 is 2.4 micrograms (mcg, or millionths of a gram), and food manufacturers add vitamin B12 to some foods, including fortified breakfast cereals. According to data from the U.S. government's NHANES (National Health and Nutrition Examination Survey), most Americans actually get more than the RDA for B12 from their diet. Vegetarians who eat no animal foods may need to take supplemental vitamin B12.

How do you know if you are B12 deficient?

The general symptoms of vitamin B12 deficiency include

  • anemia
  • fatigue
  • weakness
  • constipation
  • weight loss
  • loss of appetite
  • sores on the mouth or tongue

Neurological symptoms include

  • numbness or tingling in the hands and feet
  • problems with balance
  • depression
  • confusion
  • memory problems

Metformin and B12

Now a recent study published in Diabetes Care by researchers from Emory University has found that the people who took Metformin for the longest time had the highest prevalence of B12 deficiency. In those who took Metformin for more than 10 years, 8 percent were vitamin-B12 deficient.

And a shocker!

What is most striking about this study from Emory, however, is that when the people with type 2 diabetes took B12 supplements (up to 6 mcg of vitamin B12 per day), they were not protected from B12 deficiency; that is, their deficiency was not corrrected by a normal supplement and they remained deficient in this crucial vitamin. As expected, the supplemental B12 did reduce the prevalence of a deficiency among people without diabetes.

What does this mean for you?

Just be aware that Metformin use is associated with B12 deficiency, and that you also might need to take a higher-dose supplement to correct your deficiency. If you are concerned about the possibility of B12 deficiency, or if you have some of the symptoms above, please talk with your health care provider. Blood tests can be done to determine if you have a B12 deficiency.

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Health Highlights: Dec. 26, 2013