Dutch researchers in Maastricht and Drenthe have discovered that metformin, a drug taken by many diabetes patients to reduce the risk of cardiovascular diseases, can cause a vitamin B12 deficiency.

Vitamin B12 deficiency leads to fatigue, anaemia and memory problems. Until now doctors assumed these symptoms were the result of the diabetes or old age and could not be treated.

Vitamin B12 only occurs naturally in animal products like meat and dairy, so vegans have long been advised to take supplements. The Health Council's recommended daily dose of vitamin B12 is 2.8 micrograms.

The researchers, led by Coen Stehouwer, were involved in a study of long-term medication use among people with diabetes type 2. Approximately 800,000 people in the Netherlands have type 2 diabetes and the number is growing fast with the increase in morbid obesity.

The researchers warn that "this shows once again that serious side-effects can be discovered even in a medicine which has been use for years by millions of people."

Around 70 percent of diabetes type 2 patients in the Netherlands take metformin every day. The researchers strongly recommend adding vitamin deficiency to the guidelines for treating diabetes. As long as patients taking metformin receive regular checks, any vitamin deficiency can easily be prevented or corrected.

(Metformin is sold under many commercial names including Glucophage, Riomet, Fortamet, Glumetza, Obimet, Dianben, Diabex and Diaformin)
 

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