Short-acting (Regular) and rapid-acting insulins (Aspart, Lispro, Glulisine) are recommended for patients with type 1, type 2, or gestational diabetes. They may also be used in other types of diabetes.


Injections are given under the skin. Also suitable for insulin pumps.

Rapid-acting insulins can be injected with a traditional syringe and needle, or with a disposable pen that has been prefilled with up to 300 U of insulin. Most patients tend to prefer pens though while convenient, may be expensive. Pens are not available for regular insulin.

Three common rapid-acting insulins are:

Regular insulin is marketed by a few different companies:

These medicines are injected into the soft tissues under the skin. They act quickly and for a short period of time to help the body digest carbohydrates from meals. These insulins allow glucose from the bloodstream to enter the cells in the body so that glucose can be used as energy. They also reduce glucose release into the bloodstream.
  • Rapid-acting insulins are injected up to 15 minutes before each meal because they are absorbed by the body almost immediately and begin working within 15 minutes. They are most effective 1-2 hours after injection, and stop working in 4-6 hours.
  • Regular insulin is not absorbed as quickly, so it is usually injected 30 minutes before each meal. It begins working in 30 minutes to an hour, and is most effective 2-4 hours after injection. The effect wears off after 5-8 hours.
  • Aspart, Lispro, and Regular insulin are generally safe to use during pregnancy but always check with your doctor first.
  • Patients with kidney or liver problems can take these insulins under careful supervision by their health care providers. Smaller doses may be needed.
  • Rapid-acting insulins can be used in pumps.
  • Rapid-acting insulins are newer than insulin regular and act with a faster onset but can be more expensive.
  • These insulins can cause low blood glucose if they are injected before a meal and the patient doesn’t eat as much as expected. Low blood glucose can also result if too much insulin is injected in a short period of time. Always give the medication time to start working before injecting any additional insulin.
  • Combining insulin regular or rapid-acting insulin with oral medicines to treat type 2 diabetes may increase the risk of low blood glucose. Doses of oral and other non-insulin injectable medicines for diabetes may need to be adjusted.






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