Insulin

What Is Insulin?

Julie Lynn Marks
By Medically Reviewed by 
Reviewed:
Medically Reviewed

People with either type 1 or type 2 diabetes may need to receive injections of insulin to help their bodies regulate their blood sugar.

Insulin is a hormone that allows your body to regulate sugar in the blood.

It helps to keep your blood sugar levels from getting too high (hyperglycemia) or too low (hypoglycemia).

Insulin was discovered as a treatment for diabetes in the 1920s, and soon Eli Lily began producing the extract in great quantities.

Prior to this discovery, diabetes was considered untreatable and likely to result in death.

Special cells called beta cells in the pancreas make insulin. With each meal, the beta cells release insulin to help the body use sugar in the blood or store it.

People with type 1 diabetes cannot make insulin because their beta cells are damaged or destroyed.

Those with type 2 diabetes don't make enough insulin or the body can't use it properly.

People with either type 1 or type 2 diabetes may need to receive injections of synthetic or animal insulin to help their bodies regulate their blood sugar.

Types of Insulin

Doctors prescribe different types of injectable insulin to treat diabetes. These are:

Rapid-acting insulin: This insulin starts working about 15 minutes after you inject it into the tissue just beneath the skin.

It peaks in about one hour but keeps working for two to four hours.

It's typically taken before a meal along with a long-acting insulin.

There's also a type of rapid-acting insulin, Afrezza, that can be inhaled through the mouth, which may be more convenient for some people.

Short-acting insulin: This insulin starts working about 30 minutes after you inject it.

It peaks in about two to three hours but keeps working for three to six hours.

It's typically given before a meal along with a long-acting insulin.

Intermediate-acting insulin: This insulin starts working about two to four hours after you inject it.

It peaks in about four to 12 hours but keeps working for 12-18 hours.

It's typically taken twice a day along with a rapid- or short-acting form of insulin.

Long-acting insulin: This insulin starts working several hours after you inject it.

It keeps working for about 24 hours, and can be used with a rapid-acting or short-acting insulin.

Your doctor will help you decide what type of insulin and which form of delivery — an injection pen (such as Toujeo), a syringe, or a pump — is best for your medical condition and lifestyle.

Insulin Pump

An insulin pump is a device that can deliver rapid-acting or short-acting insulin 24 hours a day through a tiny catheter placed just under your skin.

Insulin pumps are more commonly used by people with type 1 diabetes, but those with type 2 diabetes can use them as well.

Insulin Side Effects

Insulin may cause side effects, such as:

In rare cases, insulin can cause an allergic reaction at the injection site.

Insulin Overdose

Overdosing on insulin can cause serious side effects and death.

If you suspect an overdose, contact a poison control center or go to an emergency room immediately.

You can get in touch with a poison control center at 800-222-1222.

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