Metformin and anaemia: myth or reality?

Metformin is an effective antihyperglycaemic agent used extensively in treating diabetes. It has few side effects but it may inhibit vitamin B12 absorption in the distal ileum which may potentially limit its use. This study set out to determine if there is an association between metformin treatment and anaemia in a large population with diabetes mellitus. A total of 520 consecutive patients with diabetes were studied. Anaemia was defined by World Health Organization criteria of Hb <13g/dl in men, and Hb <12g/dl in women. Serum B12 was measured in the patients with significant anaemia of Hb <11g/dl. Anaemia was present in 24.6% of the study population. There was no difference in the prevalence of anaemia and the haemoglobin levels between patients on metformin and those not on metformin. In patients with significant anaemia, there was also no difference in serum vitamin B12 levels between the two groups. Metformin remains a valuable drug in the management of diabetes. Whilst the clinician must be aware of the potential association between metformin and B12 deficiency, this study in a large population with diabetes shows no significant association between metformin and anaemia, suggesting that metformin associated anaemia is rare. Copyright © 2009 John Wiley & Sons, Ltd.