Whether or not it is useful to take insulin after eating needs to be determined by the type of insulin, which is a very effective method of controlling blood sugar in diabetics. There are many types of insulin, according to the different time of action, insulin can be divided into rapid-acting insulin analogs, short-acting insulin, intermediate-acting insulin, long-acting insulin analogs, as well as pre-mixed human insulin, pre-mixed insulin analogs and so on. Insulins that need to be injected before meals are mainly rapid-acting insulin analogs, short-acting insulin, and premixed human insulin and premixed insulin analogs, of which rapid-acting insulin analogs and premixed insulin analogs have a rapid onset of action and a short time to peak, and can be injected subcutaneously before or during meals, as well as subcutaneously immediately after meals. Short-acting insulin and premixed human insulin have an onset of action 20-30 minutes after injection, so these two types of insulin after eating and then playing will appear insulin peak lags behind the peak of the meal glucose, not only can not effectively reduce postprandial glucose, but also the possibility of preprandial hypoglycemia may occur at the next meal, if it is a rapid-acting insulin analog or premixed insulin analog, subcutaneous injection immediately after the meal is useful.