How does an insulin pump work?

Insulin pumps are small, usually battery-operated, devices that contain a cartridge filled with rapid-acting insulin. They have a built-in computer and a sensitive motor that turns very gradually to push insulin from the cartridge through a tube and into your body.  All pumps have multiple safety features that ensure against accidental insulin delivery – even under the most severe or unusual conditions.tandem_t-slim - insulin pump therapyaccu chek combo - insulin pump services with battery operated device omnipod 2010 - benefits of insulin pump therapy

The tubing that connects the pump to your body comes in various lengths and is very strong.  Some pumps are tubeless – they attach directly to the skin and are programmed with a remote control.  To get the insulin under your skin, an infusion set is worn. Most infusion sets use a needle (about the size of an insulin syringe needle) to insert a small, flexible plastic tube just under the skin, usually on the abdomen, buttocks or hip. The needle is then removed and the infusion set is taped securely in place. A new infusion set is inserted every 2 to 3 days, depending on individual usage. Many infusion sets feature a “disconnect” mechanism that allows the user to temporarily unhook the pump and tubing for situations like bathing, contact sports and intimacy.

How does an insulin pump mimic a pancreas?

The human body stores sugar in the liver. Throughout the day and night, the liver releases small amounts of sugar into the bloodstream so that we always have fuel available to burn for energy. To help shuttle this sugar into the body’s cells (and maintain the blood sugar at a steady level), the pancreas releases insulin into the bloodstream every few minutes. When we eat food that contains carbohydrates (sugar or starch), the blood sugar level rises quickly and the pancreas releases a large amount of insulin to prevent the blood sugar level from rising too high.

The insulin pump copies the human pancreas by automatically releasing small amounts of rapid-acting insulin (in tenths or hundredths of a unit) every few minutes. This is called basal insulin. The basal insulin is designed to keep the blood sugar level steady between meals and during sleep. Temporary adjustments can be made to basal insulin levels for situations such as illness, stress and exercise.

When food is eaten, the pump is programmed by the user to deliver a larger quantity of insulin very quickly. This is called bolus insulin. The bolus is designed to match the amount of carbohydrate in the food.  Boluses can also be used to lower high blood sugar levels.  Modern pumps come equipped with built-in bolus calculators that make dosing easy and accurate.  Boluses can also be extended (delivered over a period of several hours) to better match the blood sugar rise from slowly-digesting foods.

With a pump, you get large amounts of insulin when you need it, and small amounts when you don’t need as much. This type of system cannot be duplicated with multiple injections of insulin because long-acting insulins (Lantus, Levemir) do not provide the basal “peak” and “valley” that is required by most people, and NPH insulin produces an uneven and often unpredictable flow of insulin.  Only insulin pump therapy permits a careful match of both basal and bolus insulin delivery to each person’s unique needs.  And that, in turn, allows for almost unlimited schedule flexibility and a much more normal life.

Benefits of Insulin Pump Therapy

Insulin pump therapy offers a number of unique and important benefits over traditional insulin injection therapy. Here are just a few benefits of insulin pump therapy:

  1. Better blood sugar control – Statistically, people who use insulin pumps have lower HbA1c’s than people who take shots. But forget about statistics. What’s more important is that pump users see fewer highs and fewer lows, and more readings that are within their “target range.”
  2. Less trouble with lows – By eliminating long-acting insulin from the diabetes regimen and replacing it with true “basal” insulin delivery, the need to eat meals on schedule is eliminated. Meals can be delayed or skipped without worrying about hypoglycemia.  Pump bolus calculators can deduct “insulin-on-board” (insulin still working from previous boluses), thus preventing “stacking” of insulin and over-correction for high readings.  Blood sugar levels also tend to drop more gradually with pump use – resulting in earlier detection of hypoglycemic symptoms and fewer lows requiring the assistance of others.
  3. A flexible lifestyle – There are not many people who can keep the same schedule day after day. With an insulin pump, you choose when to have your meals and snacks, when to exercise, and when to sleep. Shift work and travel across time zones is much easier with an insulin pump.
  4. Precise dosing – Imagine being able to take exactly 1.85 units of insulin! The insulin pump is capable of delivering doses to the nearest tenth or hundredth of a unit with pinpoint precision. With an on-board dosing calculator and the ability to deliver in small, precise increments, the pump can be an excellent choice for those who are sensitive to small insulin doses, such as children, athletes and lean adults.
  5. Convenience – Forget about the hassle and social stigma of drawing up syringes or changing pen needles every time you need to take a shot. With the insulin pump, taking insulin is easy and discreet, anytime and anywhere. Simply press a few buttons, and your insulin is automatically delivered.
  6. No Shots – Multiple daily insulin injections can be uncomfortable and damaging to the skin.The pump’s infusion set requires a single needle stick every 2-3 days.
  7. Easy adjustments – The one constant in life is change. From childhood growth and seasonal sports to pregnancy, menses and acute illnesses, insulin needs can change from day-to-day and year-to-year. The insulin pump makes it easy to adjust your overall insulin intake to best match your needs.
  8. Weight Control – Whether your interest is in gaining or losing weight, the insulin pump gives you the power to adjust your insulin to match desired levels of food intake and physical activity.
  9. Better control with exercise – Without long-acting insulin to cause untimely blood sugar drops during exercise, hypoglycemia is less common with pump use. Pre-meal bolus adjustments make after-meal exercise easy, and temporary basal rate reductions make blood sugars more manageable during and after prolonged/intense activities.
  10. Novelty – We all like things that are new and exciting (and traditional injections are anything but). The insulin pump may be just the ticket to renew your interest and enthusiasm in your diabetes care.
  11. Historical Data – All pumps are downloadable to either web or pc-based programs for review of information such as basal/bolus history, carbohydrate entries, and blood sugar logs.  The pumps themselves also permit recall of recent diabetes-management activities.

Drawbacks to Insulin Pump Therapy

Making an educated decision about pump therapy means that you should be aware of the potential drawbacks as well.

  1. Cost – Insulin pumps and disposable pump supplies (infusion sets, cartridges, batteries) cost far more than conventional pens and syringes. However, insurance companies have come to realize that insulin pump use can result in fewer health problems. As a result, most private and public health plans cover most or all of the cost of pumps and supplies.
  2. Adjustment Period – Just as it took some time to get your blood sugars regulated when you first started on insulin injections, it will take some time to get regulated on the pump. Expect at least a few weeks of “ups and downs” as you and your health team work together to establish proper basal rates and bolus formulas.
  3. Inconvenience – While insulin pump therapy does allow greater lifestyle flexibility, wearing the pump around the clock can be inconvenient at times. The pump must be worn while you sleep, work and play in order to provide a continuous flow of insulin. However, the “beeper-like” size of the pump, availability of convenient clips and carry-cases, extra strong/durable tubing (difficult to damage or pull out), and “quick disconnect” mechanism make wearing the pump easier than it might seem.
  4. Technical Difficulties – As with any mechanical device, there are bound to be technical problems from time to time. Although today’s pumps are extremely safe, there remains the possibility of occasional infusion set clogs, computer chip glitches and damage due to typical wear and tear. Luckily, new durable materials, warning alarms and safety features minimize these types of problems.  Pump company help lines offer 24/7 assistance and quick replacement as needed.
  5. Skin Problems – One of the most common problems associated with insulin pump use involves skin irritation. Today’s infusion sets feature hypo-allergenic adhesives that truly minimize skin irritation, but those with very sensitive skin may still experience itching, rashes or inflammation. A variety of alternative tapes are available for those who need them. Skin infections are another potential problem, particularly for those with a history of staph infections.  As is the case with injection therapy, overuse of particular areas of skin can cause a breakdown of the fatty layer and problems with insulin absorption.
  6. Ketosis – Ketones are acids produced in large amounts when our body’s cells are not able to burn sugar for energy, usually due to an insufficiency of insulin. If not treated quickly, mild ketosis can become DKA (diabetic ketoacidosis), a life-threatening condition that requires emergency treatment at a hospital. Because there is no long-acting insulin with pump use, any interruption in insulin delivery (due to an infusion set problem, for example) for more than a few hours can lead to ketosis. For this reason, pump users must check their blood sugar level several times a day, and should check for ketones with any abnormally high blood glucose readings. The presence of ketones in the blood or urine usually means that the pump is not delivering insulin properly. All insulin pump users should be trained on how to respond to ketosis in order to prevent DKA.
  7. Sports & Intimacy – Wearing an insulin pump during daily recreational activities can present a challenge. Some people feel uncomfortable or inhibited while wearing the pump and choose to simply disconnect for short intervals. Some even feel uncomfortable about having the small infusion set attached to their skin. The ability to quickly disconnect and re-connect has made pump use much more convenient, but issues of vanity and personal appearance may still be a consideration.

Ingredients for Success With The Insulin Pump

It takes skilled, educated and motivated users and healthcare professionals to produce success with insulin pumps.  Insulin pumps are specialized tools that require specialists to help you use them well. Your healthcare team should include at least one person who is experienced and well versed in pump therapy and blood sugar management.

Before considering pump therapy, you should understand the role of carbohydrates in blood glucose control and be proficient at carbohydrate gram counting. Much can be learned simply by looking up carbohydrate information in books and on food labels, but a registered dietitian (RD) and/or certified diabetes educator (CDE) can help you to fine-tune your carb-counting skills. You should also learn how to properly adjust your insulin doses based on variations in carbohydrates eaten at meals/snacks, anticipated physical activity, and high/low blood sugar levels.  Finally, your pre-pump routine should include checking blood sugars at least four times daily and keeping detailed records of carbs, activity, insulin doses and blood sugars on a daily basis.
During your pump training, practice calculating bolus doses for a variety of situations. Obtain written instructions on when/how to perform infusion set changes and ask about strategies for safely disconnecting from the pump. Be sure that you are comfortable with all pump features before ending your training session. Find out how to prevent infections and diabetic ketoacidosis (DKA), and learn techniques for troubleshooting common pump problems.

Once you are “up and pumping,” make plans to communicate with your healthcare team on a daily basis.  It will be necessary to fine-tune the initial basal rates and bolus doses that were set by your physician. Testing and adjusting the basal rates will ensure that your blood sugars are holding steady between meals and while you sleep. Basal tests should be performed at all times of day (overnight, morning, afternoon and evening). Once the basal rates are confirmed, the bolus formulas (insulin-to-carb ratios and correction doses) can be adjusted properly. Make arrangements for post-pump education to cover topics such as the use of temporary basal rates, strategies for wearing the pump and controlling blood sugars during various physical activities, and the use of extended boluses.

Additional Insulin Pump Therapy Resources

The 4-1-1 on IOB (understanding insulin on board calculations):, 2010
Basal Insulin: The Foundation of Good Control: Going Forward, 2010
Type 2s: Time For Insulin? Voice of the Diabetic, 2010
Injection Aids To the Rescue! Diabetes Learning Center, 2007
Insulin-To-Carb Ratios Made Easy:, 2007
Fight the Phobia! Fear of Needles Can Be Conquered: Diabetes Learning Center, 2007
Insulin & Weight Gain: Does Tighter Control Make You Loosen Your Belt? Diabetes Learning Center, 2006
A Consumer’s Guide to Selecting an Insulin Program: Diabetes Self-Management, 2003

For assistance with technical training, preparing for or managing on an insulin pump, please give us a call!