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How long does it take for Humalog to work?

Medically reviewed by Sally Chao, MD. Last updated on July 20, 2023.

Official answer


Humalog (insulin lispro) is a rapid-acting insulin prescribed to improve blood sugar control in people with diabetes. In general, Humalog starts to work about 15 minutes after it is injected, and peak effects happen after an hour or two. Humalog's effects usually last 2-4 hours. However, this can be different for everyone, or even vary for the same person from one injection to another.

If you have diabetes, your body does not produce enough insulin or does not respond to insulin appropriately. Insulin is a hormone that enables your body to use the energy from the food you eat. You may have to give yourself insulin injections under the skin (subcutaneously), usually several times a day, to control your blood sugar.

The injections can be given under the skin of the abdomen, thigh, upper arm or buttocks. The exact dose is determined by several factors, including your current blood sugar as well as what (and how much) you are eating.

Factors that can influence the timing of insulin's effects include:

  • The injection site
  • Blood flow to the injection site
  • Body temperature

For example, exercising after giving yourself an insulin injection would increase blood flow and body temperature. Both of these factors could potentially increase the rate of insulin absorption from the injection site, which might shorten the time for initial effects and increase the degree of peak effects of the insulin.

To optimize the effects of insulin, coordinate the timing of your insulin injections with mealtimes and workouts.

  1. Food and Drug Administration (FDA). Drugs@FDA: FDA-Approved Drugs. HUMALOG (insulin lispro injection). November 2019. Available at:,205747s022s025s026lbl.pdf. [Accessed July 7, 2021].
  2. American Diabetes Association (ADA). Insulin basics. Available at: [Accessed July 12, 2021].

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