Back to Diabetes Basics Humalog (Insulin Lispro)


Humalog Vial Humalog® (lispro insulin) is a rapid-acting human insulin analog (Human analog) sold by Eli Lilly. Humalog starts to work almost immediately, compared to Regular insulin which requires about 30 minutes to begin to work. Thus Humalog can be injected right before a meal, or even immediately after a meal. For parents of children with diabetes who are picky or unpredictable eaters, Humalog might be just the tool to help match the insulin given to the food eaten.

In addition to working faster, Humalog has a shorter duration of action than Regular insulin. This means that people who use Humalog might experience fewer night-time low blood sugars, and need to eat less for their mid-morning and mid-afternoon snacks. It also means that people who use Humalog might need to increase their long-acting insulin (NPH or Ultralente for example) a little to compensate for the absence of the trailing action of Regular insulin.

Humalog is taken in the same amount as Regular insulin. It may be used with Lantus (insulin glargine), but should not be mixed with Lantus.

How Does it Work so Fast?

In Regular insulin, the individual insulin molecules clump together, six at a time, to form a hexamer. Only individual insulin molecules are biologically active, so the body must first break the bonds that hold the six insulin molecules together. Individual insulin molecules become available in about 30 minutes.

To make Lispro insulin, the positions of two amino acids in the insulin molecule, one lysine and one proline, are reversed. This rearrangement results in hexamers that bind together so weakly that they break apart much faster than regular insulin. The individual lispro insulin molecules are biologically active essentially immediately.

The timing of action of Humalog more closely resembles the way the body makes insulin in response to a meal.

Clinical Testing

Humalog has been tested in thousands of patients around the country. Testing conducted by Dr. Stuart Brink, Senior Endocrinologist, New England Diabetes and Endocrinology Center, was typical, showing excellent results in patients who received Humalog before and after meals.1 Patients involved in the tests had no problems switching from Regular to Humalog, experienced no major change in their insulin dosages, had no excessive hypoglycemia and had no need to increase their background NPH or Ultralente insulins. The duration of the test was too short to determine if patients using Humalog experience lower HbA1c readings compared with patients using Regular.

children with DIABETES has received several questions about any possible adverse effect of lispro insulin (Humalog) on the heart. This question was referred to Eli Lilly; we received a reply from from Drs. Anderson and Bastyr which stated that study data showed there was no increased risk of cardiac problems associated with the use of Humalog.2

At this time, Humalog is approved by the United States Food and Drug Administration for use in children over age 3.

Is Humalog for You or Your Child?

Humalog is a very fast acting insulin, nothing more. If your blood sugar control is good, as shown by good HbA1c readings, there is no need to switch to Humalog. The big advantage of Humalog is that it can provide greater flexibility in the timing of injections in relation to meals.

Parents of kids who are very fussy or unpredictable eaters might find Humalog to be a better tool, since they should be able to give an injection of Humalog immediately after eating. The insulin dosage can be matched more closely to the amount of food eaten, lessening the risk of hypoglycemia and hyperglycemia.

If you have a busy schedule that doesn't always permit waiting for 30 or more minutes after injecting Regular before you eat, you will also benefit from Humalog since you will be able to inject right before you eat.

Humalog Use in Pregnancy

There have been several studies looking at Humalog use in pregnancy. None showed any adverse outcomes for the baby beyond what would be expected in diabetes and some demonstrated better glucose control in the mother compared to Regular insulin. Clinical experience and the current literature suggests that Humalog is probably safe for use in pregnancy.

For more information about the use of Humalog in pregnancy, see:


  • Very fast acting -- inject and eat (or eat then inject)
  • Tested with Lilly's Humulin NPH and Ultralente
  • Excellent choice for finicky eaters
  • FDA approval for children 3 years and older
  • In the United States, available by presciption only
  • More expensive than older insulins
  • Major competitors: Regular insulin, NovoLog

For More Information


  1. E-mail from Dr. Stuart Brink, Senior Endocrinologist, New England Diabetes and Endocrinology Center; Director, Pediatric and Adolescent Diabetes and Endocrinology at Newton Wellesley Hospital and Associate Clinical Professor of Pediatrics, Tufts University School of Medicine, to Dr. William Quick, Medical Director of children with DIABETES, 14 August 1996.
  2. E-mail from Eli Lilly, to Dr. Tessa Lebinger, member of the Diabetes Team at children with DIABETES, August 12, 1996.

Updated February 11, 2007

  Home Return to Top

Last Updated: Thursday February 27, 2014 19:28:21
This Internet site provides information of a general nature and is designed for educational purposes only. If you have any concerns about your own health or the health of your child, you should always consult with a physician or other health care professional.

This site is published by T-1 Today, Inc. (d/b/a Children with Diabetes), a 501c3 not-for-profit organization, which is responsible for its contents.
By using this site, you agree to our Terms of Use, Legal Notice, and Privacy Policy.
© Children with Diabetes, Inc. 1995-2015. Comments and Feedback.