An insulin pump is a computerized device that delivers insulin to patients throughout the day and night. Growing numbers of people with diabetes use insulin pumps, especially patients with type 1 diabetes. They also benefit some people with type 2 diabetes or other forms of diabetes who need insulin.

Pumps have been used with schoolchildren, teenagers and adults. They have also been used with diabetic infants and toddlers, with pumps that parents can operate by remote control.

Insulin pumps offer flexibility because they pump insulin slowly and continuously in an imitation of the human pancreas. However, unlike the pancreas they do not make automatic adjustments based on the body's needs. As with other forms of insulin administration, patients must be vigilant in monitoring their glucose (blood sugar) levels and, when necessary, adjusting their insulin dosage according to their physician-approved treatment plan.

Insulin pumps are about the size of a cell phone and generally weigh about 3 ounces (85 grams), though some models weigh little more than 1 ounce. The pump and its delivery system are composed of the following parts:

• Pump reservoir or insulin cartridge.
  
  
• Battery-operated pump. The type of battery used varies according to the model. Some batteries last only a few weeks, others two or three months.
  
  
• Computer chip that controls how much insulin is delivered to the patient. The number of insulin rates and insulin profiles offered depends on the model. The basal range and the smallest bolus amount also vary according to model.
  
  
• Thin plastic tube. The tube from the pump has a needle-like plastic or metal tip (cannula) that is inserted under the skin, or the tube is connected to another small, soft tube (catheter) that has been inserted into the skin. A cannula is changed every few days. The junction between the tube and the cannula is called an infusion set, but often that term is used to describe the cannula or catheter. Some insulin pumps have an integrated cannula and do not require tubing.

The various models also offer extra features. These may include a glucose meter, food database, bolus calculator or data storage. Recent innovations include a unit combining an insulin pump with a continuous glucose monitor. One alternative system has a replaceable self-adhesive insulin-filled pod that is attached to the skin for several days and controlled by a wireless handheld gadget.

Some infusion sets include automatic insertion devices, and some do not need insertion devices. The insertion site is the same used when insulin is injected, usually the fatty tissue of the abdomen but possibly the thigh or arm. Insertion of the needle causes no more discomfort than injection by syringe. Use of pumps may require needle insertion only every few days rather than several times a day.

The infusion set is taped into place on the patient's body. When this is done properly, the patient does not feel it throughout the day or night. The tube and pump can be temporarily removed from the infusion set for activities such as contact sports.

Insulin pumps can be kept in a pocket or attached to a belt, shirt, underwear or other garments. The pump reservoir or cartridge holds two to three days’ worth of short-acting insulin. The small battery-powered pump pushes a plunger to force the gradual delivery of medication out of the pump, through plastic tubing and into the cannula. Insulin empties out of the cannula and is absorbed into the body. This method of delivering insulin is known as continuous subcutaneous insulin infusion.

Insulin pumps deliver the medication in three ways:

• Basal rate. This is a continuous trickle of insulin that keeps blood glucose levels stable overnight and between meals. Many pumps allow patients to set different basal rates throughout the day. Thus, a patient can program basal rates appropriate to levels of activity such as sleep or exercise.
  
  
• Bolus dose. This is a surge of insulin that occurs shortly before a person eats and prepares the body to break down the glucose in the food about to be ingested. Patients who use rapid-acting insulin can make their pump provide a burst of insulin around mealtime. Those who use regular insulin may be instructed to take a bolus dose about half an hour before eating.
  
  
• Corrective or supplemental doses

Insulin pumps are worn 24 hours a day, including overnight while the patient sleeps. This does not cause discomfort. Occasionally, patients may remove the pumps for an hour or two to engage in activities such as athletics, showering or intimacy. Some pumps are described by the manufacturer as waterproof and submersible but not recommended for use in a sauna or steam room. However, most are merely water-resistant, and they should be removed for bathing and swimming, according to the American Diabetes Association (ADA).

Infusion sets need to be replaced every one to three days. Individuals are advised to rotate the insertion site according to their physician's recommendation.

Patients who use insulin pumps must make a serious commitment to the treatment. Training may take a day or longer. Patients are required to perform glucose monitoring on the schedule recommended by their physician (generally every three or four hours, according to the ADA), and to keep a close watch on consumption of carbohydrates. When pumps quit delivering insulin for whatever reason, dangerously elevated glucose levels can quickly result. This hyperglycemia requires immediate attention.

Pumps come with built-in warning systems that alert patients when insulin flow has been halted, batteries are low or other conditions have arisen that require the patient's attention. Patients who use insulin pumps may discover hyperglycemia during periodic testing. This can be the result of many factors, including:

• Clogged or kinked tubing that prevents insulin from reaching the patient
  
• Infection or inflammation at the insertion site
  
• Expired or damaged insulin
  
• Empty insulin cartridge
  
• Problems with the infusion set, such as dislodged needle or cannula
  
• Worn-out batteries

In addition, hypoglycemia can result from problems such as an incorrect supplemental dosage by the patient.

Pumps can be temporarily removed during certain activities. However, patients generally should not keep their pump detached for more than one or two hours. Some activities that tend to lower glucose levels may allow the patient to stay detached from the pump for longer periods of time. However, individuals should discuss this beforehand with their physician.

Surgically implantable insulin pumps are being developed as an alternative to external devices.

There are also other ways of delivering insulin besides pumps and traditional syringe injections. These include:

• Insulin pen. A device resembling a fountain pen that is used to inject cartridges of insulin.
  
  

• Insulin jet injector. A pen-like device that uses high pressure to propel insulin through the skin and into the body.

In addition, some people who use insulin may be candidates for a pancreas transplant or an islet cell transplant.