Humulin is the brand name for several types of human insulin used to lower your blood sugar level if you have diabetes mellitus. Humulin R is a regular, short-acting insulin. Humulin N is an intermediate-acting insulin, also known as NPH. Humulin 70/30 is a premixed combination of regular and NPH insulin. Each type of Humulin has a different peak activity time.
Like all regular insulins, Humulin R helps to prevent your blood sugar level from rising excessively after meals. The activity of Humulin R typically peaks two to four hours after you inject the medication. To synchronize the peak activity of Humulin R with the blood sugar peak associated with eating, you inject this form of insulin approximately 20 to 30 minutes before meals.
Humulin N contains insulin in a chemical suspension that slows and prolongs its release. The peak activity of Humulin N typically occurs approximately eight hours after your injection. The duration of activity is approximately 12 to 16 hours. The activity profile of Humulin N makes it useful for maintaining a relatively constant level of insulin in your bloodstream if administered twice daily. This helps keep your blood sugar level steady between meals.
Humulin 70/30 is a premixed formulation containing 70 percent Humulin N and 30 percent Humulin R. The premixed drug is convenient if your doctor prescribes both regular and NPH insulin. Two activity peaks occur with this combination medication; one approximately two hours after injection from the regular insulin and a second lower peak approximately 10 hours after injection from the NPH insulin.
Variability in Peak Activity
The reported peak activity times for various types of Humulin are averages; your experience may be different. After using Humulin for several weeks, you and your doctor may discover from your home glucose monitoring that you are experiencing peak activity earlier or later than the reported average. If this occurs, the timing of your injections may need to be adjusted. Do not change the dose or timing of your insulin injections unless you talk with your doctor.
The peak activity of your insulin dose may also change from one day to another. The site of injection affects insulin absorption; injections into your abdomen or arm enter your bloodstream more quickly than injections into your hip or thigh. The depth of the injection also affects the rate of insulin absorption, although this is usually not an issue if you use an injection pen. Finally, your insulin dose affects the rate of absorption and peak activity, with large doses taking longer for complete absorption than smaller doses.