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Rapid-acting Insulins


Updated June 27, 2014

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Rapid-acting Insulins

Rapid-acting insulin can be injected using insulin pens

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Rapid-acting Insulins:

A rapid-acting insulin is one whose chemical structure has been change so that the insulin is more quickly absorbed into the bloodstream. This change to the chemical structure of the insulin does not affect its ability to lower blood sugar (glucose) but it does affect the rate at which the insulin is absorbed. Rapid-acting insulin is absorbed into the bloodstream within minutes and has many potential benefits for people with diabetes.

Types of rapid-acting insulins

There are currently three rapid or fast-acting insulins. The first is generically referred to as lispro but is marketed under the name Humalog and manufactured by Eli Lilly. Humalog is the oldest of the three rapid-acting insulins and has been commercially available since 1966.

A second rapid-acting insulin was approved by the U.S. Food and Drug Administration in 2000. This insulin carries the generic name of aspart but is marketed under the brand name NovoLog and is produced by Novo Nordisk.

The most recent addition to the rapid-acting insulins is called insulin glulisine and became available in 2006. It is best known by its brand name Apidra and is marketed by Sanofi-Aventis.

How rapid-acting insulin works

All three of these rapid-acting insulins are quickly absorbed into the bloodstream and begin working within about 15 minutes. Each insulin reaches their peak potency in about one hour and continues to lower blood sugar for up to five hours. This quick absorption of the insulin allows a person to inject a rapid-acting insulin just before eating to “cover” the rise in blood sugar that occurs when food is eaten. The peak potency at one hour coincides with the time that glucose is typically peaking, offsetting the rise in blood sugar.

Rapid-acting insulin in pumps

Rapid-acting insulin is also used in insulin pumps to provide a continuous but low level of insulin. This continuous flow of insulin is often referred to as basal insulin and is the ongoing insulin that is needed to manage normal fluctuations in blood sugar between meals and during sleep. Additional units of rapid-acting insulin are given at meal times (called bolus insulin) to offset the effects of rising glucose from the food you are eating.


Insulin. American Diabetes Association. " Consumer’s Guide 2011. " Diabetes Forecast, January 2011, Vol, 64, No. 1.

Hieronymus, L. M.S.Ed., A.P.R.N., B.C.-A.D.M., C.D.E., Geil, P. M.S., R.D., C.D.E. "Types of Insulin. " Diabetes Self-Management, 2009.

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