Using Insulin to Treat Type 2 Diabetes

Bottle of insulin and syringe against white background,close-up
Insulin. Leland Bobbe / Getty Images

If you have type 2 diabetes, you probably already know that a healthy lifestyle — including diet, exercise and weight control — is a very important part of your treatment. You also may need to take oral medications, either a single drug or a combination of drugs. If your type 2 diabetes is not well-controlled on oral medications, you may need to take insulin.

How Does Insulin Work?

Insulin helps keep your blood sugar levels within a normal range by moving glucose from your blood into your body’s cells. Your cells then use the glucose for energy. People who do not have diabetes make the correct amount of insulin on their own.

If you have type 2 diabetes, you may be able to control your levels of insulin and blood sugar with oral medication. However, some people with type 2 diabetes can't control their blood sugar with oral medications alone and need to add insulin injections to their treatment.

How Do I Take Insulin?

You will need to learn how to inject yourself with insulin, which you may need to take one or more times each day. Your doctor or a diabetes nurse can help you decide which method of taking insulin is best for you and will teach you how to inject yourself.

Taking injections. You will give yourself shots using a needle and syringe. Your doctor or nurse will show you how to get the correct amount of insulin into the syringe and how to inject it under your skin. Some people use an insulin pen, which looks like a pen but has a needle for its point and is prefilled with the correct amount of insulin.

Using an insulin jet injector. This device, which looks like a large pen, sends a fine spray of insulin through your skin with high-pressure air instead of a needle.

Using an insulin pump. An insulin pump is a small machine that you can wear on the outside of your body on a belt or in a pocket. The pump connects to a small plastic tube and a small needle that is inserted under your skin and stays in for several days. The machine pumps insulin through the tube into your body.

When Should I Take Insulin?

Your doctor will recommend a schedule for you that tells you when and how much insulin to take. Your schedule will depend on what type of insulin you are using and your daily routine, including when you eat your meals and how and when you exercise.

Some people with type 2 diabetes who are taking oral medications may only need a single shot of insulin each day. Others may need insulin injections two, three, or four times a day to reach their blood glucose targets.

What Types of Insulin Are Available?

Each type of insulin works at a different speed. The different types of insulin vary in how long they are active in your body.

For example, rapid-acting insulin starts to work within 15 minutes after you take it and works for about three to five hours. Long-acting insulin starts to work within one hour after you take it and works about 24 hours. Some people with type 2 diabetes need two or more types of insulin to reach their blood glucose targets.

Each type of insulin has an onset, a peak, and a duration time.

  • The onset is how soon the insulin starts to work to lower your blood sugar after you inject it.
  • The peak is the time the insulin is working the hardest to lower your blood sugar.
  • The duration is how long the insulin lasts in your body — the amount of time it keeps lowering your blood sugar.

Because each person with type 2 diabetes is different, the onset, peak, and duration times may be different. Your diabetes health care team will work with you to come up with an insulin plan that works best for you.

The following are some of the commonly prescribed types of insulin:

Rapid-acting insulin
Onset: 5 to 15 minutes
Peak: 30 to 90 minutes
Duration: 3 to 5 hours


  • Apidra (insulin glulisine)
  • Humalog (insulin lispro)
  • NovoLog (insulin aspart)

Short-acting insulin
Onset: 30 to 60 minutes
Peak: 2 to 4 hours
Duration: 5 to 8 hours


  • Humulin R (regular insulin)
  • Novolin R (regular insulin)

Intermediate-acting insulin
Onset: 1 to 3 hours
Peak: 8 hours
Duration: 12 to 16 hours, but can last as long as 24 hours


  • Humulin N (NPH insulin)
  • Novolin N (NPH insulin)

Long-acting insulin
Onset: 1 hour
Peak: no peak
Duration: 20 to 26 hours


  • Lantus (insulin glargine)
  • Levemir (insulin detemir) (this medication is dose dependent so it may last for as little as 6 hours)

Pre-mixed insulin
Since some people with diabetes need to take two different types of insulin to control their blood sugar, mixtures of intermediate-acting insulin and either rapid-acting insulin or short-acting insulin are available.

Onset: 5 to 60 minutes
Peak: varies
Duration: 10 to 16 hours


  • Humalog 50/50 (50% intermediate-acting + 50% rapid-acting)
  • Humalog 75/25 (75% intermediate-acting + 25% rapid-acting)
  • Humulin 50/50 (50% intermediate-acting + 50% short-acting)
  • Humulin 70/30 (70% intermediate-acting + 30% short-acting)
  • Novolin 70/30 (70% intermediate-acting + 30% short-acting)
  • NovoLog 70/30 (70% intermediate-acting + 30% rapid-acting)

What Are the Side Effects of Insulin?

Possible side effects of insulin include:

  • low blood glucose (hypoglycemia)
  • weight gain

The combination of insulin with oral medications used to treat type 2 diabetes increases your risk of low blood sugar especially if you exercise more than usual or if you have skipped, delayed, or eaten too little.

A member of your diabetes team will review the signs of low blood sugar with you and will instruct you about the things you should do when your blood sugar is too low.

On a final note, if you're taking insulin for diabetes, you may want to consider using a new technology called continuous glucose monitoring (CGM). Typically, people who take insulin for type 2 (or type 1) diabetes need to perform several uncomfortable finger pricks a day to test for blood glucose levels. CGM is an implantable device that continuously monitors levels of blood glucose without the need for numerous daily finger sticks. However, between three and four finger pricks are still required to calibrate the machine.

The use of CGM will help keep track of your blood glucose levels during times that you would normally not be able to check your blood glucose levels, such as while asleep or while exercising. Using this information, your physician can adjust your insulin dosages to better reflect your needs and provide better glycemic control. CGM is recommended by various diabetes associations and is sometimes covered by insurance. If interested, please ask your physician about CGM.

Type 2 Diabetes Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

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