The DIA or duration of insulin action is how long a bolus lowers the glucose. An accurate DIA must be entered in the pump to prevent insulin stacking when boluses are given close together. Stacking can occur any time a previous carb and correction bolus is still lowering your glucose when a new bolus is given. An accurate DIA time allows the BC to properly calculate subsequent carb and correction boluses once the first bolus of the day has been given.
It takes a minimum of 4 to 6 hours for all of the glucose-lowering activity of a recent bolus of rapid insulin to stop lowering the glucose. Insulin has little effect on the glucose for the first 15 to 20 minutes, reaches a halfway point in activity at just over 2 hours, and has the other half of activity tail off over about 5 to 6 hours after the bolus is given.
Today’s pumps allow the user to select a wide range of times for the DIA with possible settings between 1.5 and 8 hours in most pumps. This wide range is designed to handle faster genetically-engineered insulins that may appear in the future, as well as older Regular insulin. However, this range is far wider than the action time for the rapid-acting insulins currently in use. Every pump comes with a default setting for DIA. This default setting can often be changed to a more effective and sometimes safer setting.
An appropriate DIA setting for today’s insulins (Novolog [aspart], Apidra [glulisine], and Humalog [lispro]) is between 5 and 6 hours.13-18 A DIA time shorter than this will hide bolus insulin activity and hide insulin stacking. Pumping Insulin has a full discussion of how to avoid hidden insulin stacking.
Read more about Duration of Insulin Action.