Skip to content
My WebMD Sign In, Sign Up

Insulin is a hormone that treats diabetes by controlling the amount of sugar in the blood.

There are many types of insulin used to treat diabetes. They are classified by:

  • How fast they start to work
  • When they reach their "peak" (the concentration of insulin in your blood is highest)
  • How long their effects last

The types of insulin include:

Rapid-acting insulin. This starts working within a few minutes and lasts for a couple of hours.

Regular- or short-acting insulin. It takes about 30 minutes to work fully and lasts for 3 to 6 hours.

Intermediate-acting insulin. This takes 2 to 4 hours to work fully. Its effects can last for up to 18 hours.

Long-acting insulin.  There are no peak levels in the bloodstream, and it can keep working for an entire day.

It's possible that you may need more than one type of insulin or multiple shots a day. You may also need to space your insulin doses throughout the day to keep your blood sugar levels stable throughout the day.

There are other medications that can be used along with insulin therapy. If you can't control your blood sugar with insulin therapy alone, your doctor may prescribe an additional drug that acts like the hormone amylin. People with diabetes often don't have enough amylin, which enhances the action of insulin.

How Is Insulin Given for Diabetes?

Insulin for diabetes can be injected under the skin. It can be injected using a needle and syringe, a cartridge system, or prefilled pen systems. Insulin pumps are also available.

A rapid-acting inhaled insulin device is also available. 

Where on the Body Should Insulin Be Injected?

The place on the body where you inject your insulin may affect the timing of its benefit to you. Insulin is absorbed the fastest and the most consistently when it is injected into the abdomen. The next best places to inject your insulin are the arms, thighs, and buttocks.

You should try to consistently inject insulin at the same general site on your body. This helps keep the absorption of insulin constant. But you should alternate the location of the exact injection spot within that general area. This helps prevent the breakdown and scarring of fat tissue under the skin.

What Are the Side Effects of Insulin?

The major side effects of insulin taken for diabetes include:

  • Low blood sugar
  • Lumps or scarring of the area of the body that has received too many insulin injections
  • Rash at the site of injection or over the entire body (rare)
  • Weight gain at the start of therapy

How Should I Store My Insulin?

Always keep two bottles of each type of your insulin on hand. The bottle that you are using may be stored at room temperature (not higher than 80 F) for 30 days. Store it where it will not get too hot or too cold and keep it out of direct sunlight.