The rapid-acting insulin required by the amount of carbohydrates contained in the meal or in order to correct blood sugar is delivered using a pump button, a remote control or separate controller. The mealtime insulin delivered by the pump is called mealtime bolus.
In pump therapy, as in multiple daily injections (MDI) therapy, the relative amount of insulin required for a meal, known as the Insulin to Carbohydrate Ratio (ICR), is determined. The ICR may vary at different times of the day. For instance, many people need a larger mealtime insulin dose in the morning than at other times of the day. With pump therapy, it's easy to set a different ICR for different times of the day.
The rapid-acting insulin required for a meal should be administered 10–20 minutes before starting to eat, as in MDI, unless the blood sugar is low. Additionally, the mealtime insulin can be administered at different rates. Depending on the pump, you can take a standard dose, a slow dose, or a two-part or combination dose.
If the pump has the option for a slow dose, the slow dose can be adjusted for a specific duration. For example, the 6 units needed for a meal can, instead of a regular single dose, be set to be taken over a certain period of time slowly. This can be beneficial for prolonged meals or if stomach emptying is delayed.
If the pump has the option for a combination dose, part can be administered immediately and the remainder over a set period of time slowly. For instance, pizza or pasta contains slow carbs and fat that delays absorption. From the mealtime dose, one might take 70 percent immediately and 30 percent over a few hours.
In the new so-called hybrid pumps, the dose can be divided into two parts if needed by inputting part of the meal's carbohydrates into the pump before the meal and the remaining carbohydrate portion at the desired time, e.g., 1–2 hours after the meal.