Metformin works by lowering the amount of Glucose added by our Livers. It is also said to improve Insulin resistance a little, and is generally thought to help the cardio vascular system. When i got my numbers down to non diabetic, my gp suggested sticking with the minimum dose, purely for the benefits to my Peripheral Artery disease. I'm also now on a low dose of Dapaglaflozin. Not for diabetic reasons, but to aid my kidneys, which could be said to be due to diabetes. The half life of Metformin is 72 to 96 hours, so 3 to 4 days to reach the dosed for level, and the same to clear the system when stopping.