Insulin Replacement Therapy

March 21, 2017

Insulin Replacement Therapy

Insulin replacement therapy and type 1 and 2 diabetes

Type 1 diabetes is an autoimmune disease in which the body's immune system attacks the cells that make insulin. This results in no or very little insulin. Type 1 diabetes is also called insulin-dependent diabetes. It usually 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 pump.

Type 2 diabetes typically means the body cannot make enough insulin for the amount of insulin resistance. Insulin resistance means the body cannot use insulin the way it should. Treatment often begins with an exercise program and a healthy diet to help lower the blood sugar levels. But if this treatment plan doesn't work, you may need medicine. Medicines for diabetes may be pills or injections.

What is insulin?

Insulin is a hormone made by the pancreas. It helps lower the blood sugar by moving sugar from the bloodstream into the cells of the body. Once inside the cells, blood sugar becomes the main source of energy for the body.

What are the different types of insulin?

There are 4 types of insulin. Each works in specific ways.


How quickly the insulin starts to work after it is 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 vary. The 4 types of insulin are:

Insulin type


Peak time


Rapid acting, Lispro, Aspart, Glulisine insulin

15 minutes

1 hour

2 to 4 hours

Short acting, Regular (R) insulin

30 minutes

2 to 3 hours

3 to 6 hours

Intermediate acting, NPH (N) or Lente (L) insulin

2 to 4 hours

4 to 12 hours

12 to 18 hours

Long acting, Glargine, Detemir insulin

1 to several hours


24 hours

Source: American Diabetes Association

Some people with diabetes may need to take 2 different types of insulin to control their blood sugar levels. Some insulin can be bought already mixed together, such as Regular and NPH insulin. This lets you inject both types of insulin at the same time. Other types of insulin cannot be mixed together and may need 2 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.

Most recently, an inhaled form of insulin has become available. This is a form of rapid-acting insulin. 

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

  • Your type of diabetes--whether you have type 1 or type 2 diabetes

  • Your daily schedule of meals, work, and activity

  • How willing you are to monitor 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. It gets into the bloodstream by injecting it into the fat layer, usually 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 abdominal wall works the fastest. Injecting it into the thigh works the slowest. Insulin must be given by injection. It cannot be taken by mouth because it is destroyed in the stomach during digestion.

The timing of insulin injections is very important. Rapid or short-acting insulin usually needs to be given before mealtimes, or before sugar from a meal starts to enter the bloodstream. Always talk with your healthcare provider about your own insulin treatment. He or she 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. Long-acting insulin should be taken at the same time every day, but your meal times can be flexible. Intermediate-acting insulin or mixed insulin needs to be taken at the same time every day along with a fixed eating schedule.

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 the most common device used to give insulin. The needle of the syringe is placed under the skin, and the insulin is injected.

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.

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 inject a “bolus” of insulin as needed. The pump is small enough to be worn on a belt or in a pocket.

Insulin by mouth

Because insulin is quickly broken down during digestion, it has always been given by injection, usually just under the skin. But new medicines and techniques may protect insulin from being broken down in the digestive tract.

The first trials of oral insulin in people were reported in 2006. Phase I clinical trials have shown that insulin given in a gel capsule may be safe and work well. Clinical trials will continue over the next several years as the medicine moves through the federal approval process.

Pancreas transplant

In type 1 diabetes, the pancreas makes too little insulin or none at all. Replacing a pancreas with a healthy transplanted pancreas would seem to be a cure for type 1 diabetes.

In the 1960s, pancreas transplants were first attempted. But it was not until the surgical techniques improved and new medicines were developed years later that pancreas transplants became a realistic treatment for type 1 diabetes. Pancreas transplants continue to be 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 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 the antirejection medicines that 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. The best success rates have been achieved with this type of procedure. 

  • Pancreas after kidney transplant (PAK). In this procedure, a pancreas is transplanted into a person who has already received a kidney transplant. This procedure generally has a success rate near that of SPK procedures.

  • Pancreas transplant alone (PTA). In this procedure, only the pancreas is transplanted. This type of procedure is done less often. It generally has a lower success rate than the other procedure types.

Pancreas islet cell transplantation

The islet cells in the pancreas make insulin. Only about 1% to 2% 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. Research continues on the Edmonton Protocol, in a multicenter trial being done by the Immune Tolerance Network. Sponsors for the Immune Tolerance Network are the National Institute of Allergy and Infectious Disease, the National Institute of Diabetes and Digestive and Kidney Diseases, and the Juvenile Diabetes Research Foundation.

Islet cell transplants are a noninvasive procedure. This means no 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.

People who get an islet cell transplant must take antirejection medicine to protect the transplanted islets from being rejected and destroyed by the body’s normal immune system.

Insurance and insulin pumps

Be sure to check with your insurance company to find out if blood glucose monitoring equipment and insulin pumps are covered under your plan. Medicare has covered the cost of insulin pumps since 1999.


March 21, 2017


General Principles of Insulin Therapy in Diabetes Mellitus. UpToDate

Reviewed By:  

Hurd, Robert, MD,Sather, Rita, RN