The normal reference range of fasting blood sugar is 3.9-6.1mmol/L. Insulin plays a very important role in controlling blood sugar to within the normal range. If fasting blood glucose is 6.6mmol/L, it is a state of high fasting blood glucose. Although it is a state of high blood glucose, it already indicates an early deficiency of insulin secretion or the existence of early insulin resistance. For this group of patients, it is recommended to do standard glucose tolerance test and measure insulin level at the same time. If insulin secretion is indeed problematic or insulin resistance exists, early intervention treatment with metformin can be given. Early intervention treatment will bring blood glucose levels down to the normal range and prevent progression to diabetes.