Lantus (insulin glargine) and Metformin can be taken together and is commonly used to treat Type 2 diabetics. According the a recent study in Germany, the incidence of hypoglycemia is
lower when taking these in combination. Metformin is used to increase the bodies sensitivity to insulin which helps people with Type 2 diabetes since they have built up a tolerance to insulin. Lantus will then supplement Metformin for any deficiency in insulin. In type 1 diabetics Metformin is prescribed with Lantus for various reasons including weight control and polycystic ovary disease. In summary, the only thing to worry about is the possibility of hypoglycemia. Otherwise, there seems to be no reported drug interaction between the two.