Overview of the Types of Insulin

How each type works in the body to help manage diabetes

Vials of insulin

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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 vital for controlling type 1 diabetes (diabetes mellitus). It's also the first-line treatment for gestational diabetes, a temporary form of the disease that can develop during pregnancy. Insulin also may be necessary to help manage type 2 diabetes in people for whom 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 doctors, this means there are lots of options for tailoring treatment to patients' specific needs. It also means that the prospect of taking insulin may feel overwhelming—and even scary, as insulin must be injected directly into the body. If you're prescribed insulin to treat diabetes, it can help to understand the important role the hormone plays health as well as some basic differences between types of insulin.

The Importance of Insulin

Insulin, which is produced by specific cells in the pancreas called beta cells. Its job is to help the body use or store the glucose that's derived 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 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, which can result in a number of serious, and even life-threatening, consequences.

The pancreas produces two types of insulin:

  • 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 in direct response to the ingestion of food in order to manage the rise in blood glucose that immediately follows.

Types of Replacement Insulin

The various types of supplemental insulin are designed to replace both bolus and basal insulin, they actually are differentiated based on three characteristics:

  • Onset: How much time lapses between when the insulin is injected and when it starts to affect blood sugar levels amount of time between your injection and when the insulin starts to lower your blood sugar.
  • 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, intermediate-acting (sometimes referred to as regular), 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 as well. 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, as detailed here, there may be more than one brand.

Characteristics of Different Insulin Types
Type of insulin Onset (time it takes to reach the bloodstream) Duration Peak Brand and generic names
Rapid-acting 15 minutes 2 to 4 hours After 1 hour Apidra (insulin glulisine)
Admelog, Humalong (insulin lispro), Fiasp, NovoLog (insulin aspart)
Short-acting 30 minutes 3 to 6 hours Between 2 and 3 hours Humulin R, Novolin R, Velosulin R (human regular)
Intermediate-acting 2 to 4 hours 12 to 18 hours At 4 to 12 hours Humulin N, Novolin N, ReliOn (NPH)
Long-acting Reaches bloodstream several hours after injection 24 hours or longer N/A Tresiba (degludec), Levemir (detemir), Basaglar, Lantus (glargine)
Ultra long-acting 6 hours 36 hours N/A Toujeo (glargine u-300)
Note: Because long-acting and ultra long-acting insulins are designed to stay in the system for extended periods of time, they do not have peak action points.

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

Premixed Insulins

Premixed insulins, which combine varying amounts of intermediate-acting insulin with rapid-action or short-acting insulin, are 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 also is one form of insulin that can be inhaled called Afrezza (technosphere insulin-inhalation system). Approved by the U.S. Food and Drug Administration in 2015, 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

Learning you need to take insulin in order to manage diabetes may be daunting, but you can trust your doctor will work closely with you to make sure both your dose and the type of insulin you're prescribed align with your lifestyle. He or she also will provide all the support you need to become comfortable with injecting your insulin or using a pump if that turns out to be the best option for you.

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