Supplemental insulin—a manufactured version of the hormone naturally produced by cells in the pancreas to regulate levels of glucose (sugar) in the blood—is used to control blood sugar in type 1 diabetes (diabetes mellitus).

It’s also a treatment for gestational diabetes, a temporary form of diabetes that can develop during pregnancy.

Insulin also may be necessary to help manage type 2 diabetes when lifestyle changes and oral medications aren’t enough to keep blood sugar levels stable.

According to the American Diabetes Association (ADA), there are more than 20 types of insulin sold in the United States. For healthcare providers, this means there are lots of options for tailoring treatment to patients’ specific needs.

If you’re prescribed insulin to treat diabetes, it can help to understand the important role the hormone plays in your health as well as some basic differences between types of insulin.

The Importance of Insulin

Insulin is produced by specific cells in the pancreas called beta cells. Its job is to help the body use or store the glucose that comes from carbohydrates in the diet. Glucose is necessary for every bodily function; it circulates in the bloodstream and is taken up by cells for energy.

When the body doesn’t produce enough insulin (as in the case of type 1 diabetes) or when it becomes resistant to using insulin properly (as happens with gestational and type 2 diabetes), cells are no longer able to access the energy they need, and glucose builds up in the blood.

This can result in a number of serious, and even life-threatening, consequences.

The pancreas produces insulin in two different ways:

  • Basal insulin (sometimes called background insulin) regulates glucose levels between meals and is released 24 hours a day, whether or not a person eats.Bolus insulin is released by the pancreas to manage the rise in blood glucose that immediately follows eating food.

Types of Replacement Insulin

Supplemental insulin comes in different types, and some are designed to replace bolus insulin, while others replace basal insulin.

The different types of insulin are differentiated based on three characteristics:

  • Onset: The time between the insulin injection and when it starts to affect blood sugar levels.Duration: How long insulin continues to work after taking effect.Peak: The point at which insulin is working at maximum capacity.

The ADA lists five types of supplemental insulin: rapid-acting, short-acting (sometimes referred to as regular), intermediate-acting, long-acting, and ultra long-acting.

Rapid and Short-Acting Insulins

Both types are used to replace the natural bolus insulin produced by the pancreas. Because they begin to work quickly, they’re used just before meals or snacks to offset the immediate rise in glucose levels that will occur from eating.

Intermediate-Acting Insulin

There is only one type of intermediate-acting insulin on the market—neutral protamine Hagedorn (NPH). The duration of NPH can vary significantly, so it’s not uncommon for people who use it to also take a dose of regular or rapid-acting insulin to cover meals.

NPH looks different from other types of insulin. Unlike the clear fluid that characterizes short- and rapid-acting insulins, NPH has a cloudy consistency caused by crystals of insulin in the solution.

Long-Acting and Ultra-Long-Acting Insulin

Intermediate, long-acting, and ultra-long-acting insulins are used to replace basal insulin with the goal of keeping blood glucose levels consistent throughout the day and night.

They begin working about two hours after injection and are released slowly, peaking at four to eight hours after injection, and lasting for at least 24 hours.

Within each type of insulin, there may be more than one brand.

Besides these standard types of insulin, there are a couple of other options.

Premixed Insulins

Premixed insulins combine varying amounts of intermediate-acting insulin with rapid-action or short-acting insulin. They can be a convenient way to obtain the benefits of both types of insulin in one injection.

They have an onset of between 15 minutes and one hour, depending on the mix. The peak time varies and each can last up to 24 hours.

Inhaled Insulin

There is one form of insulin that can be inhaled called Afrezza (technosphere insulin-inhalation system). Approved by the Food and Drug Administration in 2014, it’s a rapid-acting insulin that begins working within 12 to 15 minutes, peaks at around 30 minutes, and is cleared from the system in three hours.

A Word From Verywell

You might feel intimidated by the idea of taking insulin. Your healthcare provider will work closely with you to make sure that your dose and the type of insulin you’re prescribed align with your lifestyle. Your medical team will provide the support you need to become comfortable with injecting your insulin or using a pump.

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By Gary Gilles

Gary Gilles is a licensed clinical professional counselor (LCPC) who has written about type 1 diabetes and served as a diabetes counselor. He began writing about diabetes after his son’s diagnosis as an infant.