In type II diabetes treated with metformin (Glucophage) lactic acidosis is a rare adverse reaction, fatal in approximately 50 per cent of cases. Metformin is implicated by plasma and intra-erythrocyte levels. An analysis is carried out on available information about this risk for healthcare professionals and for patients. A comparison is made of approved labelling information on Glucophage and its patient leaflets in France and in the USA and an analysis made of the differences. In France, Information given to physicians, pharmacists and patients on the risk of lactic acidosis where Glucophage is implicated must be improved, and on the interest of the metformin plasma level in this case. These are primary points because the issue for the few patients concerned may be fatal. Advice on self-medication may be introduced. The evolution of information provided on these risks depends on the pharmaceutical laboratory, government authorities and healthcare professionals.