Short-acting insulin takes effect in 15-60 minutes. Short-acting insulin is a type of human insulin synthesized by recombinant technology, with peak effect time of 2-4 hours and duration of action of 5-8 hours. Short-acting insulin is injected subcutaneously 15-30 minutes before a meal, which is exactly at the peak time of high blood glucose 0.5-1 hours after eating, and can achieve a better effect of reducing postprandial blood glucose. If you forget to inject short-acting insulin before meal, you cannot give supplementary injection after meal, and you need to wait for a period of time before eating after injecting short-acting insulin, which is inconvenient to use and can also cause weight gain. At present, most of the clinical applications of rapid-acting insulin analogues have the advantages of fast onset, low incidence of hypoglycemia, and avoiding weight gain, and can eat immediately after injection, and those who forget to inject can make up for it after meals.