Insulin Replacement Therapy

Insulin replacement therapy and type 1 and 2 diabetes

Type 1 diabetes is an autoimmune disease. The body's immune system attacks the cells that make insulin. As a result, the body makes very little insulin, or no insulin. Type 1 diabetes is also called insulin-dependent diabetes. It often happens at a younger age. It often starts before age 30. Treatment for type 1 diabetes includes getting daily multiple injections of insulin or using an insulin pen or pump. An inhaled insulin is available but isn't used as often. A pill form of insulin is being developed and may be available in the near future.

Type 2 diabetes typically means the body can't use insulin correctly. This is called insulin resistance. Treatment often begins with making changes in your lifestyle to help lower your blood sugar levels. This includes diet, exercise, and weight loss. But if this treatment plan doesn't work, you may need medicine. Medicines for diabetes may include insulin pills or injections, or other medicines.

What is insulin?

Insulin is a hormone made by the pancreas. It helps lower the level of sugar (glucose) in your blood. It does this by moving sugar from the blood into the body's cells. Once inside the cells, blood sugar becomes the body's main source of energy.

What are the different types of insulin?

Insulin varies based on the onset, peak, and duration. Each works in certain ways.


How quickly the insulin starts to work after it's injected

Peak time

The period of time when the insulin helps most to lower blood sugar levels


How long the insulin keeps working in the body

Insulin may act differently when given to different people. So the times of onset, peak time, and duration may be different. There are four main types of insulin:

Insulin type

Onset (approximate)

Peak time (approximate)

Duration (approximate)

Rapid-acting, lispro, aspart, glulisine insulin, inhaled

15 minutes

1 to 2 hours

2 to 4 hours

Short-acting, regular (R) insulin

30 minutes

2 to 3 hours

3 to 6 hours

Intermediate-acting, NPH (N) insulin

2 to 4 hours

4 to 12 hours

12 to 18 hours

Long-acting, glargine, detemir insulin, degludec

several hours


24 hours

Ultra long-acting, glargine U-300

6 hours


36 hours or longer

Source: American Diabetes Association

Some people with diabetes may need to take two different types of insulin to control their blood sugar levels. Some insulin can be bought already mixed together. This includes regular and NPH insulin. This lets you inject both types of insulin in one injection. Other types of insulin can't be mixed together. They may need two separate injections.

Insulin is made at different strengths. U-100 insulin (100 units of insulin per milliliter of fluid) is the most common strength. The syringes for giving insulin are different for each different strength. This means a U-100 syringe can be used only with U-100 insulin.

Recently, an inhaled form of insulin has become available. This is a form of rapid-acting insulin. An ultra-long-acting insulin has also been developed. This insulin begins to work in 30 to 90 minutes, does not peak, and lasts for over 40 hours.

The type of insulin chosen may reflect your choice and how well you are able to follow any given treatment. Other factors include:

  • If you have type 1 or type 2 diabetes

  • Your daily schedule of meals, work, and activity

  • How willing you are to check your blood sugar levels regularly

  • How much exercise you get each day

  • How well you understand diabetes

  • How stable your blood sugar levels are

  • Your diet

How is insulin given?

Insulin has to enter the body's bloodstream to work. Currently, insulin must be given by injection. It can't be taken by mouth because it is broken down in the stomach during digestion. An oral form that can make it through the stomach is also being developed. But for now, to get it into the blood, it must be injected into the fat layer under the skin. This is often done in the arm, thigh, or belly. Different sites on the body allow the insulin to enter the blood at different rates. Insulin injected into the belly wall works the fastest. Injecting it into the thigh works the slowest.

The timing of insulin injections is very important.

  • Rapid-acting and short-acting insulin. This usually needs to be given before meals. Or before sugar from a meal starts to enter the bloodstream.

  • Intermediate-acting insulin or mixed insulin. This needs to be taken at the same time every day along with a fixed eating schedule.

  • Long-acting insulin. This should be taken at the same time every day. But your mealtimes can be flexible.

Always talk with your healthcare provider about your own insulin treatment. They can tell you where to inject the insulin, how much to inject, and how often. Your provider can tell you the times of day you should take it. Bring your glucose testing results to your appointment. Your provider can help you make the adjustments needed in your insulin schedule and dosing.

What are the different types of insulin injection devices?

Many types of insulin injection devices are available. Some examples of devices include:




The syringe is one of the most common devices used to give insulin. The needle of the syringe is used to draw insulin out of a bottle and then to inject it under the skin.

Insulin pen

An insulin pen is like a preloaded syringe that can be used multiple times. It is often used for multiple, daily doses of insulin. The insulin pen holds a cartridge with insulin. The pen looks like a writing pen. It has a small needle that can be screwed on at the tip. A dial on the pen lets you set the right dose. A plunger on the other end of the pen is used to actually deliver or inject the insulin.

Smart pens, now called connected insulin pens, are also available. These pens can be programmed to calculate insulin doses. They can also send data to your smartphone.

Insulin jet injector

An insulin jet injector looks like a large pen. The injector makes high-pressure air to "spray" the insulin through the skin.

External insulin pump

An insulin pump is a device that pumps insulin continuously through plastic tubing. The tubing is attached to a needle under the skin near the belly. It can also be used to inject a single, large dose (bolus) of insulin as needed. The pump is small enough to be worn on a belt or in a pocket.

Pancreas transplant

In type 1 diabetes, the pancreas makes too little insulin, or no insulin at all. Replacing a pancreas with part or all of a healthy transplanted pancreas would seem to be a cure for type 1 diabetes.

The first pancreas transplants were tried in the late 1960s. But it was not until the surgery methods improved and new medicines were developed years later that pancreas transplants became a realistic treatment for type 1 diabetes. Pancreas transplants are still studied at many centers in the U.S. and around the world. It is the standard treatment in certain cases.

When successful, a pancreas transplant cures diabetes. Or it at least reduces the number of severe episodes of low and high blood glucose. Blood sugar levels become normal because the new pancreas makes insulin. But as with most types of solid organ transplants, complications may happen. The most common complications include rejection of the new organ, infection, and harmful effects from antirejection medicines. These medicines must be taken for life after the transplant.

Pancreas transplants can be done in 3 ways:

  • Simultaneous pancreas and kidney transplant (SPK). Most people with type 1 diabetes who meet the criteria for pancreas transplant also have kidney disease. So surgeons often transplant both a pancreas and a kidney at the same time. This type of transplant has had the best success rates.

  • Pancreas after kidney transplant. A pancreas is transplanted into a person who has already been given a kidney transplant. This procedure generally has a success rate near that of SPK procedures.

  • Pancreas transplant alone. Only the pancreas is transplanted. This type of procedure is done less often. It generally has a lower success rate than the other procedures.

Pancreas islet cell transplantation

The islet cells in the pancreas make insulin. Only about 1 or 2 out of 100 of the cells in the pancreas are islet cells.

In the 1970s, research into islet cell transplants in mice was very successful. But transplants in people were not as successful. Researchers at the University of Alberta in Edmonton, Alberta, Canada, developed a special way of transplanting the islet cells that shows great promise. But research continues.

Islet cell transplants are considered a minor surgery. No cut (incision) is needed. Islet cells are taken from a donor pancreas and then injected into the recipient's liver through a long, thin tube (catheter). Once the islet cells have been implanted in the donor, they begin to make and release insulin. But the failure rates are high after the first year or two. Islet cell transplants can also be done from a person's own pancreas (autotransplant). A person may be a candidate for this procedure if they are having their pancreas removed because they have severe chronic pancreatitis (inflammation of the pancreas) and some of the insulin-producing cells are still active. People with type 1 diabetes are not eligible for an autotransplant since their pancreas contains few if any healthy insulin-producing cells.

People who get an islet cell transplant from a donor must take antirejection medicine. This protects the transplanted islets from being rejected and destroyed by the body’s normal immune system. Considerable progress has been made in obtaining insulin-producing cells from stem cells. These could make more cells than are usually available through islet cell transplant procedures.

Insurance and insulin pumps

Check with your insurance company to find out if blood glucose monitoring equipment and insulin pumps are covered under your plan. Medicare Part B covers the cost of insulin pumps and supplies if you meet certain requirements.

Online Medical Reviewer: Raymond Kent Turley BSN MSN RN
Online Medical Reviewer: Robert Hurd MD
Online Medical Reviewer: Ronald Karlin MD
Date Last Reviewed: 8/1/2023
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