INTRODUCTION Diabetes mellitus is a group of metabolic disorders characterized by hyperglycemia due to insulin deficiency or resistance or both reasons. (1) According to this, diabetes mellitus can be divided into type I and type II. It is a common phenomenon and its incidence is increasing, 171 million people suffered from diabetes in 2000 and this condition is expected to double in 2030. It is widespread in all countries and has therefore become a serious burden on healthcare facilities . (2)“To manage diabetes, patients must take diabetes treatment. There are two main treatments. They are diet treatments and tablet treatments. Oral antidiabetic drugs sulfonamides (sulfonylureas) and guanidine derivatives (biguanides) are used by 30% of all diabetics. (6) Metformin is a biguanide that is an effective oral anti-hyperglycemia drug widely used to control type II diabetes mellitus and more recently in pregnancy. (7)INSULIN AND GLUCAGONThe pancreas, in addition to the digestive process, has two important hormones, insulin and glucagon, which are important for maintaining the blood glucose level within a narrow range. Not only glucose, but they are also important for protein and lipid metabolism. Glucagon is secreted by the alpha cells of the islet of Langerhans while insulin is secreted by the beta cells of Langerhans. Both are secreted into the portal vein. (8) ACTION OF INSULIN Immediately after a meal rich in carbohydrates, insulin is secreted rapidly due to the absorption of glucose into the blood. The action of insulin on many tissues of the body and its turnover causes rapid absorption, storage and use of glucose in almost all tissues of the body, but especially by muscles, adipose tissue and the liver. (8) ACTION OF GLUCAGON The hormone glucagon has several functions t...... half of the article ...... not only used in type II diabetes, but also in gestational diabetes mellitus. It is an effective and safe treatment for pregnant mothers suffering from diabetes. It also helps normalize the menstrual cycle and increases the rate of spontaneous ovulation and can improve hirsutism. (7) (5) (4)CONCLUSION Diabetes mellitus is a syndrome causing a relative or absolute deficiency of insulin and characterized by hyperglycemia. The most common type is type II diabetes mellitus. Metformin, a drug from the biguanide group, is the first-line treatment for diabetes mellitus. Hypoglycemia does not usually occur with metformin, and other advantages are the lower incidence of weight gain. It is absorbed mainly in the intestine, inhibits epetia gluconeogenesis and increases insulin sensitivity. Metformin is contraindicated in patients with hepatic, renal, cardiac and respiratory insufficiency.