External Insulin Pump

In the past 20 years, a new technology to deliver insulin has become increasingly popular. An external insulin pump frees people with diabetes from daily injections and gives them more flexibility in eating and other aspects of their lives, such as sleeping late in the morning. It allows for closer management and more intensive control of the disease. This, in turn, leads to fewer complications and a healthier life. 

However, it is a mistake to think that a pump takes over the management of diabetes. The person using the pump must determine doses, program the pump to deliver those doses and continue self-monitoring to keep track of blood glucose levels and make dosage adjustments when necessary. A pump does not allow a person to forget that he has diabetes. On the contrary, one of the most important qualifications for a successful pump user is strong motivation to keep control of the disease.

Insulin pumps cost about $5,000. Some health plans will pay for them.

How they work

The insulin pump is housed in a small plastic case, about the size of a pager, that most people wear attached to their belts. Inside the case is a battery-operated pump, a reservoir to hold the insulin and a computer chip that releases a programmed amount of insulin.

The pump is attached to a thin, flexible plastic tubing connected to a very fine needle that is inserted into the skin and held in place with tape. Most people insert the needle into the abdomenal wall. It is recommended that the needle site be moved a couple of inches every three days to prevent infection.

The pump case is waterproof, or has a waterproof covering, so the pump can be left on while showering or bathing. Removal is simple, however, for those who want to take it off during participation in contact sports or other strenuous physical activities.

Dosage decisions

One of the most important things to know about an insulin pump is that it doesn't have a brain. It doesn't think for the user. It does not measure blood glucose levels or determine how much insulin should be delivered. An insulin pump is referred to as an "open loop" system. Perhaps sometime in the future a device will be designed that constantly measures blood glucose and responds to the measurement by triggering the pump to inject the appropriate dose of insulin. However, that type of "closed loop system is not yet a technological reality.

Only rapid-acting regular or lispro insulins are used with a pump. The longer-acting preparations are not necessary because the pump continuously injects insulin 24 hours a day. Dosages through the pump are divided into two categories, basal and bolus, which roughly correspond in action to the intermediate/long-term and quick-acting insulins that are administered through injections. The basal rate provides a maintenance level of insulin throughout the 24 hours. This rate can be changed for certain periods; for example, 1 unit per hour may be needed during the day, but only 0.6 units per hour overnight. Usually the basal dose accounts for about 40 percent of the total daily insulin dose. The size of the bolus doses, given to cover meals and snacks, is determined according to the number of calories in the carbohydrates in the food and beverage that will be consumed. Exercise is also a factor in calculating dosage; the more exercise, the less insulin needed.

Frequent blood glucose monitoring (at least four times a day) is recommended for people using insulin pumps. One reason is that the needle can become dislodged without the user
being aware of it. This could quickly lead to high blood glucose (hyperglycemia) and even ketoacidosis if it remains undetected.

Using a pump is a big step for a person with diabetes. It should only be done in consultation with a doctor who is a diabetes specialist, a dietitian and a nurse-educator. The companies that manufacture pumps also have trainer-consultants who work with new patients; many of these representatives are insulin pump users themselves.

Last Updated: 6/23/2003
The Johns Hopkins University 1996-2003.  All rights reserved.  This information is not intended to provide advice on personal medical matters, nor is it intended to be a substitute for consultation.