Insulin is usually administered by subcutaneous injection. Insulin is classified according to the onset and duration of action: 1. Fast-acting insulin: The onset of action is 5-10 minutes, so it can be injected subcutaneously before, during, or after meals. 2. Short-acting insulin: The onset of action of short-acting insulin is half an hour after injection, so you can eat half an hour after injection. 3. Medium-acting insulin: The peak time of medium-acting insulin is 2-4 hours after injection and lasts 6-8 hours. 4.Long-acting insulin: There is no clear peak, and it lasts for 24-36 hours. According to the different ratios of rapid-acting, short-acting and intermediate-acting insulins, premixed insulins are made, such as the common insulins Menthol 30, Novolin 30R/50R, Gansulin 30R/50R, and Eugenol 25, etc. These are made by premixing rapid-acting or short-acting insulins with intermediate-acting insulins, which can be injected daily before breakfast and dinner to effectively control blood sugar in general.