the recommended dose to take is 500 mg of metformin, two or three times per day for patients over 40 who do not have kidney or liver problems, or a history of congestive heart failure, as aging causes insulin resistance.Metformin increases hypothalamo-pituitary sensitivity that declines with age.As we get older, there is a loss of sensitivity of the hypothalamus and the peripheral tissues to the effects of insulin, which causes elevated blood insulin levels (hyperinsulinemia).