A group of drugs, of which METFORMIN is the only one available for treatment, used to treat non-insulin-dependent diabetics who are overweight, when strict dieting and treatment with SULPHONYLUREAS have failed. Metformin acts mainly by reducing GLUCONEOGENESIS and by increasing the rate at which the body uses up glucose. Hypoglycaemia (low blood sugar) is unusual, unless taken in overdose. Side-effects such as anorexia, nausea, vomiting and transient diarrhoea are common initially and may persist, particularly if large doses are taken. Metformin is not given to patients with renal failure, in whom there is a danger of inducing lactic acidosis. (See also DIABETES MELLITUS.)