There are several different types of insulin available for the treatment of diabetes. Primarily insulin is of three types. They are: Rapid-acting insulin: This type of insulin is designed to work quickly, typically within 15 minutes after injection. It reaches its peak effectiveness level within one hour but has a short duration of action, typically lasting for three to five hours. Rapid-acting insulin is typically used to control blood sugar levels after meals. Short-acting insulin: This type of insulin takes longer to begin working than the rapid-acting insulin, typically starting to work within 30 minutes to one hour after injection. It reaches its peak level of effectiveness within two to four hours, and it has a longer duration of action, typically lasting for six to eight hours. Short-acting insulin is typically used to control blood sugar levels before meals. Intermediate-acting insulin: This type of insulin takes even longer to begin working than short-acting insulin, typically starting to work within two to four hours after injection. It reaches its peak level of effectiveness within four to 12 hours, and it has a longer duration of action than short-acting insulin, typically lasting for 12 to 18 hours. Intermediate-acting insulin is typically used to provide a steady background level of insulin throughout the day.