An insulin pump is a small, computerized device that delivers a continuous, regulated stream of rapid-acting insulin, replacing the need for multiple daily injections. The device delivers insulin through a tiny tube and cannula inserted under the skin, which significantly improves glucose control and flexibility for people managing diabetes. It is programmed to provide two types of doses: a constant background rate (basal) and active doses (bolus) for meals or high blood sugar. Operating the pump involves understanding the pre-programmed settings and mastering the physical application to ensure consistent and safe insulin delivery.
Initial Setup and Programming
The first step in using an insulin pump involves programming the internal ‘software’ that dictates how insulin is calculated and delivered. This begins with setting the Basal Insulin, the continuous background dose that keeps blood sugar stable between meals and overnight. This rate is measured in units per hour and can be programmed with different values throughout the 24-hour cycle to match the body’s varying insulin needs, which is a major advantage over long-acting injections.
The pump’s ability to recommend meal and correction doses relies on two personalized factors determined with a healthcare provider. The Insulin-to-Carbohydrate Ratio (ICR) defines the number of carbohydrate grams one unit of insulin will cover; for example, a 1:10 ratio means one unit covers 10 grams of carbohydrates. The Correction Factor, also known as the Insulin Sensitivity Factor (ISF), indicates how much one unit of insulin is expected to lower the blood sugar level. These programmed settings are the foundation for all subsequent insulin delivery and must be regularly reviewed and adjusted.
Physical Application and Site Management
Connecting the pump requires careful preparation and proper insertion of the infusion set, which includes a cannula placed under the skin. Before insertion, a new reservoir must be loaded with insulin and connected to the tubing. The tubing then needs to be “primed” to push out any air bubbles, which could otherwise prevent accurate insulin delivery. Air bubbles can reduce the intended dose, leading to unexpected high blood sugar levels.
The infusion set is inserted into the subcutaneous fat layer using an automatic or manual insertion device after the skin has been cleaned and dried. The set must be changed every two to three days to minimize infection risk and ensure consistent insulin absorption. Rotating the insertion site is extremely important and should involve moving between approved areas.
Approved Insertion Sites
- Abdomen
- Upper buttocks
- Arms
- Thighs
Repeatedly inserting the cannula into the same area can lead to lipohypertrophy, which are firm, fatty lumps that develop under the skin and cause erratic insulin absorption. Insulin delivered into these areas is absorbed slowly and unpredictably, often resulting in unexplained high blood sugar levels and increased insulin requirements. Avoiding these affected areas for several months allows the tissue to heal and restores consistent insulin action.
Day-to-Day Operation (Bolusing)
The most frequent interaction with the pump is “bolusing,” the on-demand delivery of insulin needed to cover carbohydrate intake or lower an elevated blood sugar level. To calculate the necessary dose, the user checks their blood sugar or continuous glucose monitor (CGM) reading and inputs the estimated carbohydrate count for the upcoming meal into the pump’s calculator. The pump then uses the pre-programmed ICR and Correction Factor to suggest a precise dose, which the user confirms for delivery.
Timing the bolus is known as “pre-bolusing,” which involves delivering the insulin 15 to 20 minutes before starting a meal. This slight delay allows the rapid-acting insulin to begin working before the carbohydrates are fully digested, helping to prevent a sharp spike in blood glucose immediately after eating. For most standard meals consisting mainly of carbohydrates, a Normal Bolus is used, where the entire calculated dose is delivered immediately over a few minutes.
Meals high in fat, protein, or low-glycemic carbohydrates are digested more slowly, which a standard bolus may not effectively cover. For these situations, the pump offers specialized bolus types. An Extended or Square-Wave Bolus spreads the insulin delivery evenly over a set period, such as two to four hours. A Combination or Dual-Wave Bolus delivers a portion of the insulin immediately and extends the remainder over time, better matching the slower digestion and absorption of complex or heavy meals.
Troubleshooting Alarms and Supply Changes
Insulin pumps are equipped with alarms designed to alert the user to an interruption in insulin delivery or a mechanical issue. The occlusion alarm is one of the most common alerts, signaling a blockage preventing the pump from pushing insulin through the tubing or cannula. An occlusion can be caused by a kinked cannula at the insertion site, a blockage within the tubing, or a problem with the insulin cartridge.
If an occlusion alarm sounds, the immediate response is to check the infusion set for visible kinks, tubing, and the cartridge. Since an undelivered dose can quickly lead to high blood sugar and the risk of ketones, the most reliable fix is often to insert a completely new infusion set in a different location. Other alerts include low reservoir warnings, indicating low insulin, and low battery alerts, both requiring straightforward replacement of the empty component.
When the pump must be removed, such as for swimming or certain medical scans, it is important to manually disconnect the infusion set. Users must always keep backup supplies, including insulin pens or syringes, in case of pump failure, which ensures that insulin delivery can continue without interruption. Knowing how to quickly address these alerts and mechanical issues is a core part of safe pump management.