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Insulin: Why You Need It and How to Use It

What is insulin?

Insulin is a hormone that controls the level of blood sugar (also called glucose) in your body. People with diabetes may not have enough insulin or may not be able to use it properly. The sugar then builds up in the blood and overflows into the urine, passing out of your body unused and depriving you of an important source of energy.

Why do I need insulin?

All people with type 1 diabetes, and some people with type 2, need to take insulin to help control their blood sugar levels. Type 1 means your body doesn't make any insulin. Type 2 means your body either doesn't make enough or doesn't use it properly.

The goal is to keep your blood sugar level in a normal range as much as possible to keep you healthy. Over time, high blood sugar levels can cause serious health problems.

How often will I need to take insulin?

Your doctor will work with you to develop a schedule that works for you. Most people with diabetes who take insulin need at least 2 insulin shots a day for good blood sugar control. Some people take 3 or 4 shots a day.

Do I need to monitor my blood sugar level?

Yes. If you don't already monitor your blood sugar level, you will need to learn how. Your doctor will teach you.

When should I take insulin?

You and your doctor should discuss when and how to take your insulin. Each person's treatment is individualized. Some people who use Regular insulin or a longer-acting insulin take it 15 to 30 minutes before a meal. Some people who use insulin lispro (Humalog), take it just before they eat.

Types of insulin

Quick acting, such as insulin lispro (Humalog), begins to work very quickly (5 to 15 minutes) and lasts 3 to 4 hours.

Short acting, such as Regular (R) insulin, starts working within 30 minutes and lasts about 5 to 8 hours.

Intermediate acting, such as NPH (N) or Lente (L) insulin, starts working in 1 to 3 hours and lasts 16 to 24 hours.

Long acting, such as Ultralente (U) insulin, doesn't start to work for 4 to 6 hours, but lasts 24 to 28 hours.

NPH and Regular insulin mixture, two types of insulin mixed together in one bottle, starts working in 30 minutes and lasts 16 to 24 hours.

Source: Medicine for People with Diabetes. National Diabetes Information Clearinghouse, NIH Publication No. 98-4222, November 1997.

Where should I inject the insulin?

Ask your doctor which place you should use. Insulin injected near the stomach works fastest, while insulin injected into the thigh works slowest. Insulin injected into the arm works at medium speed.

How do I take insulin?

Insulin is normally injected under the skin with a very small needle. It can also be taken with an insulin pen. Your doctor will teach you how to inject insulin. Follow your doctor's advice. Here are some general tips on using insulin:

  1. Wash your hands.

  2. Take the plastic cover off of the insulin bottle and wipe the top of the bottle with a cotton swab dipped in alcohol.

  1. Pull back the plunger of the syringe, drawing air into the syringe equal to the dose of insulin that you are taking (measured in units). Put the syringe needle through the rubber top of the insulin bottle. Inject air into the bottle by pushing the syringe plunger forward. Turn the bottle upside down.

  1. Make sure that the tip of the needle is in the insulin. Pull back on the syringe plunger to draw the correct dose of insulin into the syringe.

  2. Make sure there are no air bubbles in the syringe before you take the needle out of the insulin bottle. If there are air bubbles, hold the syringe and the bottle straight up, tap the syringe with your finger and let the air bubbles float to the top. Push on the plunger of the syringe to move the air bubbles back into the insulin bottle. Then withdraw the correct insulin dose by pulling back on the plunger.

  1. Clean your skin with cotton dipped in alcohol. Grab a fold of skin and inject the insulin under the skin at a 90-degree angle. (If you're thin, you may need to pinch the skin and inject the insulin at a 45-degree angle.)

What happens if I take too much insulin?

If you take too much insulin it will lower your blood sugar level too much, and you may get hypoglycemia (also called an insulin reaction). When you have hypoglycemia, you may feel cranky, more tired than usual, confused and shaky and sweat more. In serious cases, you can pass out or have a seizure. Talk to your doctor about how to treat hypoglycemia. Your doctor may suggest that you always carry a snack with you, such as candy, fruit juice or regular soda to treat hypoglycemia.

How can I learn more?

For more information, talk to your doctor. You can also learn more by visiting the web site of the American Diabetes Association at

This is a general overview on this topic and may not apply to everyone. To find out if this handout applies to you and to get more information, talk to your doctor.

Visit for more useful information on this and many other health-related topics.

Copyright 1999 by the Medisoft

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