Types of Insulin and How They Work

Insulin is a hormone the body makes to control the level of glucose (sugar) in the blood. It lowers blood sugar by allowing glucose to leave the bloodstream and enter body cells. Without enough insulin, the level of glucose in the bloodstream can become too high.

Everyone needs insulin to use food properly. People without diabetes make enough of their own insulin to keep their blood sugar at healthy levels all the time.

People with type 1 diabetes no longer make insulin of their own. Instead, they need to take shots of one or more types of insulin to keep their blood sugars close to normal. Between 75 and 90 percent of people with type 2 diabetes need to take insulin shots to help them get the best control of their blood sugar levels.

Deciding How Much Insulin to Take

The amount of insulin a person needs depends on:

When you first start taking insulin shots, your doctor might ask you to change the amount you take or the time you take it several times. You and your doctor will base these changes on the results of your blood sugar tests. You'll need to make adjustments until you find the dose and schedule that work best for you.

Each person's need for insulin is different:

If you take several insulin shots a day or use more than one type of insulin, it doesn't mean your diabetes isn't in good control. Your blood sugar, not the amount or type of insulin you take, is the best way to judge how well you are doing.

If you take three shots a day and your blood sugar is near normal, that's good. If you take diabetes pills or one shot a day, but your blood sugar is high, you probably need to change your diabetes care plan.

Types of Insulin

There is a large letter or number on the label of your insulin. The letter stands for the generic name of the insulin. The types of insulin are listed below. The first word is the generic name and the second word is a brand name under which the insulin is sold.

LP = lispro (Humalog)
A = aspart (NovoLog)
GL = glulisine (Apidra)
R = regular (Novolin R)
N = NPH (Novolin N)
G = glargine (Lantus)
D = detemir (Levemir)

Lispro, aspart, and glargine are all analog insulin, which means they've been genetically modified to work more quickly or slowly in the body.

Basal (Background) Insulin

Some types of insulin work continuously, up to 24 hours, which is similar to how a normal pancreas produces insulin. Continuously acting insulin is called background or basal insulin. Basal insulin is slowly absorbed and is long lasting, which means active from 10 to 24 hours, depending on which kind of basal insulin you use.

Background or basal insulin includes:

Mealtime Insulin

These types of insulin are designed to quickly take care of the sugar a person eats. These types of insulin are fast acting and don't last very long.

Mealtime insulin includes:

Combination Insulin

These are mixtures of long-lasting and fast-acting insulin. Manufacturers claim that the combination gives the benefit of both actions. However, the most likely effect is later action with a stronger peak.

Combination insulin includes (not to be confused with 75/25 insulin-Lispro protamine and Lispro insulin combined):

Other combinations of insulin are available on the market, such as NPH and Novolog mixtures and NPH and Lispro mixtures. These are designed for convenience because fewer shots are needed. Combinations must be carefully tailored to the individual, if used at all.

Preparing and Injecting Insulin

Learning how to prepare and take insulin is a very important part of treatment and self-management. Make sure you know how to give yourself the right kind and amount of insulin at the right time. If you're not sure, ask a member of your health care team to show you how to do it correctly.


Clinical review by David McCulloch, MD
Group Health
Reviewed 03/01/2014