Diabetes: Why You Need Insulin 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. This deprives you of an important source of energy.

Why do I need to take 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 diabetes means your body doesn't make any insulin. Type 2 diabetes means your body either doesn’t make enough insulin or doesn’t use it properly.

The goal of taking insulin is to keep your blood sugar level in a normal range as much as possible so you’ll stay healthy. Over time, high blood sugar levels can cause serious health problems such as blindness and kidney failure.

Insulin can't be taken by mouth. It's usually taken as shots. It can also be taken by pump. It may become available as a nasal spray or in other forms.

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 need 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 you will take your insulin. Each person’s treatment is different. 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 (brand name: Humalog) take it just before they eat.

Types of insulin

Rapid-acting (such as insulin lispro, insulin aspart and insulin glulisine) begins to work in 5 to 15 minutes and lasts 2 to 5 hours.

Short-acting (such as regular (R) insulin) starts working in 30 to 60 minutes and lasts about 3 to 8 hours.

Intermediate-acting (such as insulin NPH (N) human) starts working in 1 to 4 hours and lasts 12 to 18 hours.

Long-acting, (such as insulin glargine and insulin detemir), starts working within 1 to 10 hours and lasts up to 24 hours.

Pre-mixed insulin is a combination of two types of insulin (usually an intermediate-acting insulin and a rapid- or short-acting insulin).

Where should I inject the insulin?

Pull back on the plunger to draw insulin into the syringe.

Picture 1. Pull back on the plunger to draw insulin into the syringe. The usual places to inject insulin are the upper arm, the front and side of the thighs, and the abdomen (tummy area). 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:

Clean the injection area using cotton and alcohol (top). Pinch an area of skin and inject insulin (bottom).

Picture 2. Clean the injection area using cotton and alcohol (top). Pinch an area of skin and inject insulin (bottom).

  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 that you have dipped in alcohol.
  3. 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.
  4. 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 (PICTURE 1).
  5. 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.
  6. Clean your skin with cotton dipped in alcohol (PICTURE 2, top). Grab a fold of skin and inject the insulin at a 90-degree angle (PICTURE 2, bottom). (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 you may 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 (not diet) soda, to treat hypoglycemia.

How can I learn more?

For more information, talk to your family doctor.

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Written by familydoctor.org editorial staff.

American Academy of Family Physicians

Reviewed/Updated: 01/09
Created: 09/00