There are four main types of insulin, as well as insulin combination medications. The four main types are:

Insulin was once obtained exclusively from pig or cow pancreas. Today, regular and intermediate-acting insulins are referred to as human insulins, because they are manufactured to be identical to the insulin produced by the human pancreas. Rapid- and long-acting insulins are chemically modified forms of human insulin.

Most individuals need to use more than one type of insulin, so they either mix two types of insulin together or buy prepared (premixed) insulin mixtures. The insulin types differ in three ways:

  1. Onset—the length of time it takes for the insulin to reach the bloodstream and begin lowering blood glucose.
  2. Peak activity—the period of time during which insulin has its maximum effect in lowering blood glucose.
  3. Duration—the amount of time the insulin continues to lower blood glucose.

Regular or short-acting insulin

This type of insulin is manufactured to be similar to the insulin produced in the human body. Popular brands have an "R" (for regular) in their names, for example, Humulin R and Novolin R.

Regular insulin is typically injected 30–60 minutes before meals and usually reaches the bloodstream within 30 minutes, in time to cover the rise in blood glucose that begins after food is eaten. Insulin action peaks one and a half to two hours after injection and the effects last about eight to 10 hours.

Rapid-acting insulin

Insulin aspart (Novolog), insulin lispro (Humalog), and insulin glulisine (Apidra) are called insulin analogues, because their chemical structure is a modified form of human insulin that is designed to work more quickly and peak faster than regular insulin. These manufactured insulins are safer to use because they work more closely to how natural insulin functions in the body. Consequently, they are more effective in preventing high blood glucose (hyperglycemia) after meals and are less likely to produce hypoglycemia.

Rapid-acting insulin must be injected immediately before meals because it starts to work within five to 15 minutes. You must eat right away after injecting or your glucose will drop too low. Peak action occurs in 30–60 minutes, with a short duration of action of four to six hours. Novolog, Humalog, and Apidra are sold only by prescription, as their effects in children and pregnant women aren't known.

In June 2014, the U.S. Food and Drug Administration (FDA) approved Afrezza (insulin human) Inhalation Powder—rapid-acting inhaled insulin to treat adults with type 1 diabetes and type 2 diabetes that requires mealtime insulin. Afrezza is administered at the beginning of each meal or within 20 minutes of starting each meal.

In people with type 1 diabetes, the medication is used in combination with long-acting insulin and in people with type 2 diabetes, it may be used with oral anti-diabetes medications. Afrezza is not recommended to treat diabetic ketoacidosis or for people who smoke. The drug carries a Boxed Warning indicating that it should not be used in people with chronic lung conditions, like COPD or asthma, due to an increased risk for acute bronchospasm (narrowing and/or obstruction of the respiratory airway causing cough and wheezing). Side effects include hypoglycemia, cough, and throat irritation. Additional studies are being conducted.

According to our sister publication, Diabetes Focus Winter 2014, people with type 1 or type 2 diabetes who rely on insulin may be able to use Afrezza at the start of each meal. Inhaled insulin is broken down in the body more quickly than injected insulin, so it takes some of the guesswork out of mealtime doses and lessens the risk of post-meal glucose fluctuations. Afrezza isn't a substitute for long-acting insulin and isn't recommended for for people who smoke.

Intermediate-acting insulin

This type of human insulin called NPH insulin contains protamine, which makes the solution cloudy and slows the absorption of insulin. NPH insulins have an "N" in their names, for example, Humulin N and Novolin N.

After injection, intermediate-acting insulins reach the bloodstream within two to four hours and show peak action in four to eight hours. Duration of action is from 12–20 hours. Intermediate-acting insulin is often used in combination with regular or short-acting insulin.

Long-acting insulin

Both insulin glargine (Lantus) and insulin detemir (Levemir) are long-acting insulin analogues. They are often used alone in people with type 2 diabetes, or in combination with a more quick-acting insulin.

Lantus is a clear solution in the vial, but it precipitates in the skin after injection. This precipitation greatly slows the absorption of Lantus, making it very long acting, usually 18–24 hours. Levemir also is absorbed slowly, because it binds to the protein albumin in the skin. Its effects last 14–18 hours.

The FDA approved insulin degludec injection (Tresiba) in September 2015. This long-acting insulin medication can be used to control blood sugar in adults with type 1 and type 2 diabetes. It is administered once daily and the dose is individualized to meet each patient's needs. Tresiba should not be used in patients with diabetic ketoacidosis (increased ketones in the blood or urine). As with other diabetes medications, close medical supervision to monitor for allergic reactions and serious side effects is necessary. Side effects include low blood sugar (hypoglycemia) and injection site reactions.

Insulin combinations

Most individuals with diabetes use a combination of insulin types. Regular or rapid-acting insulin is generally needed before meals to reduce the after-meal increase in blood glucose levels. Intermediate- or long-acting insulin is the usual choice at bedtime to control blood glucose levels overnight.

Regular or rapid-acting insulin can be combined in the same syringe with intermediate-acting NPH insulin but not with the long-acting insulins Lantus and Levemir. Because NPH insulin can modify regular and rapid-acting insulin, it's best to inject the combination within five minutes of mixing the two insulin types.

Combining regular or rapid-acting insulin with intermediate-acting insulin can be simplified with the use of premixed products. Your physician can prescribe a 70/30 mixture, which contains 70 percent NPH and 30 percent regular insulin, or a 50/50 mixture, which contains 50 percent NPH and 50 percent regular insulin. Premixed products containing insulin aspart or insulin lispro with an intermediate-acting insulin also are available. However, the fixed ratio of the two insulin types in premixed products is unsuitable for many people because the quantity of each insulin cannot be adjusted to match the specific foods eaten at each meal.

Insulin degludec/insulin aspart injection (Ryzodeg 70/30) is a combination insulin medication (long-acting and rapid-acting forms of insulin) approved by the FDA in September 2015 to treat type 1 and type 2 diabetes in adults. Patients using this medication should be monitored closely for serious side effects and allergic reactions. In people with type 1 diabetes, Ryzodeg 70/30 is used with mealtime insulin. In people with type 2 diabetes, it is used once or twice daily. Ryzodeg should not be used in patients with diabetic ketoacidosis.

Insulin adjuncts

Symlin (pramlintide) is for people who inject insulin but have not achieved adequate glucose control. It is a synthetic version of a hormone produced by the pancreas called amylin, which blocks the release of glucose from the liver, slows the passage of food from the stomach to intestines, and suppresses appetite. Symlin must be injected before meals. A recent review found that Symlin users lowered their HbA1c levels by up to 0.7 percent and lost 4 lbs, on average.

Updated by Remedy Health Media

Publication Review By: Written by: Christopher D. Saudek, M.D.; Simeon Margolis, M.D., Ph.D.

Published: 20 Apr 2009

Last Modified: 01 Oct 2015