Insulin for Type 1 and Type 2 Diabetes


The different types of insulin are categorized according to how fast they start to work (onset) and how long they continue to work (duration). The types now available include rapid-, short-, intermediate-, and long-acting insulin.


Generic NameBrand Name
insulin aspart NovoRapid
insulin glulisine Apidra
insulin lispro Humalog


Generic NameBrand Name
insulin regular Humulin R, Novolin ge Toronto


Generic NameBrand Name
insulin NPH Humulin N, Novolin ge NPH


Generic NameBrand Name
insulin detemir Levemir
insulin glargine Lantus


Generic NameBrand Name
insulin regular/insulin NPH Humulin 30/70, Novolin ge 30/70, Novolin ge 40/60, Novolin ge 50/50
insulin lispro/lispro protamine Humalog Mix25, Humalog Mix50
insulin aspart/aspart protamine Novomix 30


Injectable insulin is packaged in small glass vials (bottles) and cartridges that hold more than one dose and are sealed with rubber lids. The cartridges are used in pen-shaped devices called insulin pens.

How insulin is taken

Insulin usually is given as an injection into the tissues under the skin (subcutaneous). It can also be given through an insulin pump, an insulin pen, or jet injector, a device that sprays the medicine into the skin. Some insulins can be given through a vein (only in a hospital).

Research is ongoing to develop not only new forms of insulin but also insulin that can be taken in other ways, such as by mouth.

How It Works

Insulin lets sugar (glucose) in the blood enter cells, where it is used for energy. Without insulin, the blood sugar level rises above what is safe for the body. If the cells don't get sugar to use for energy, they try to use other nutrients in the body. When this happens, acids can build up. Too much acid production (ketoacidosis) can be serious or even life-threatening.

Your body uses insulin in different ways. Sometimes you need insulin to work quickly to reduce blood sugar. Your body also needs insulin on a regular basis to keep your blood sugar in a target range.

  • Rapid-acting and short-acting insulins reduce blood sugar levels quickly and then wear off.
  • When you use intermediate- or long-acting insulin with rapid- or short-acting insulins, the longer acting insulin starts taking effect when the shorter acting insulin begins to wear off.
  • Usually people who take insulin use a combination of a rapid- or short-acting and an intermediate- or long-acting insulin. This can help keep blood sugar levels within a range that is safe for the body throughout the day.

Why It Is Used

Insulin is used to treat:

  • People who have type 1 diabetes.
  • People with type 2 diabetes whose pancreas produces little or no insulin or whose other diabetes medicines do not control their blood sugar. These people may take insulin either by itself or along with other diabetes medicine.
  • People with type 2 diabetes whose blood sugar levels are high because of a severe illness or major surgery. After blood sugar levels return to a target range, these people may be able to stop taking insulin.
  • Women with type 2 diabetes who are pregnant and cannot keep their blood sugar levels in a target range with diet and exercise.
  • Women with type 2 diabetes who are breastfeeding and cannot keep their blood sugar levels in a target range with diet and exercise. Sometimes other medicine for type 2 diabetes, such as metformin or glyburide, is used during pregnancy.

How Well It Works

Insulin is effective in reducing blood sugar levels by helping sugar (glucose) enter the cells to be used for energy.

Some things that affect how fast and how well an insulin dose works are:

  • Where the dose is given. If you give insulin into your abdomen (especially above and to the side of your belly button), the medicine will get into your system more consistently from day to day. If the medicine is given into a muscle or a small blood vessel instead of fatty tissue, the medicine will get into your system faster.
  • How much insulin is given. Higher doses of insulin reduce the blood sugar level more than lower doses.
  • Whether you have exercised before or just after taking insulin. If you have just exercised the muscles in the area where you give your insulin injection, the medicine will get into your system faster.
  • If you apply heat to the area. The medicine will get into your system faster if you take a hot bath or shower, put on a heat pack, or massage the area where you have just given your insulin injection.
  • If you do not have enough fluid in your body (you are dehydrated). You will not have as much blood flow to your skin, so insulin will not be absorbed as well.

Know how to give an insulin injection.

Diabetes: Giving Yourself an Insulin Shot
Diabetes in Children: Giving Insulin Shots to a Child

Side Effects

All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.

Here are some important things to think about:

  • Usually the benefits of the medicine are more important than any minor side effects.
  • Side effects may go away after you take the medicine for a while.
  • If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.

Call 911 or other emergency services right away if you have:

  • Trouble breathing.
  • Swelling of your face, lips, tongue, or throat.
  • Passed out (lost consciousness), or you suddenly become very sleepy or confused. You may have low blood sugar, called hypoglycemia.

Call your doctor if you have:

  • Hives.
  • Problems with frequent high or low blood sugar levels.

Common side effects of this medicine include:

  • Low blood sugar.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

The insulin pump provides a way to give insulin with less frequent injections, and it is as effective as multiple daily injections at keeping blood sugar levels in a target range.

Don't share insulin pens with anyone else who uses insulin. Even when the needle is changed, an insulin pen can carry bacteria or blood that can make another person sick.

The long-acting insulin glargine (Lantus) may help prevent some people from having frequent nighttime low blood sugar levels. It may also help people who have had trouble keeping their blood sugar levels in their target range with intermediate-acting insulin.

Giving short-acting insulin at the evening meal and NPH at bedtime instead of giving them together at the evening meal may reduce the risk of nocturnal hypoglycemia and hypoglycemia unawareness.

Things to check

Label each insulin bottle when you use it for the first time.

Store insulin properly so that its effectiveness is protected.

When you buy insulin, check the generic or brand names to make sure you are buying the correct type. For example, if you have been using Humulin R (insulin regular), make sure you buy Humulin R instead of Humulin N (insulin NPH).

Know when your prescribed types of insulin start working (onset), when they work most (peak), and how long they work (duration).

Taking medicine

Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.

There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.

Advice for women

If you are pregnant, breastfeeding, or planning to get pregnant, do not use any medicines unless your doctor tells you to. Some medicines can harm your baby. This includes prescription and over-the-counter medicines and natural health products. And make sure that all your doctors know that you are pregnant, breastfeeding, or planning to get pregnant.


Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

Complete the new medication information form (PDF) ( What is a PDF document? ) to help you understand this medication.


ByHealthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Anne C. Poinier, MD - Internal Medicine
Kathleen Romito, MD - Family Medicine
Adam Husney, MD - Family Medicine
Specialist Medical Reviewer David C.W. Lau, MD, PhD, FRCPC - Endocrinology
Rhonda O'Brien, MS, RD, CDE - Certified Diabetes Educator

Current as ofDecember 7, 2017

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