Insulin on Board (IOB)

The Insulin On Board (IOB) indicator on the t:slim X2 insulin pump shows the amount of insulin — from food and correction boluses — that is currently active in the body, along with an estimate of how long it will remain active (i.e., Time Remaining). The IOB always displays on the Home and Lock screens.

Control-IQ Technology

Insulin on Board is tracked slightly differently when Control-IQ technology is enabled. IOB now includes all basal insulin delivered above or below the programmed Basal Rate, not just insulin from bolus deliveries. Additionally, the Time Remaining is not displayed on the Home screen, as Control‑IQ adjusts insulin delivery every five minutes as needed.

When Control-IQ technology reduces or pauses basal insulin delivery compared to your Personal Profile settings, the Insulin on Board decreases accordingly. If your IOB was already low, this may result in the pump interpreting your IOB as a negative value. During this time, the displayed IOB will appear as zero rather than the negative value, and if you deliver a bolus, the full amount may not be reflected in the IOB.

Here are three different scenarios:

A. Negative IOB is Small

Control-IQ technology reduced basal insulin delivery when the IOB was already low. The pump displays zero since the actual IOB is a negative value.

B. Negative IOB is Large

Control-IQ technology reduced basal insulin delivery when the IOB was already low. The pump displays zero since the actual IOB is a negative value and remains negative even after a bolus delivery.

C. IOB is Zero

The actual IOB is zero and the units displayed on the pump match that value.

Note: You can always check the Current Status or Pump History to verify the bolus delivery amount.

Always refer to the user guide for important safety information and detailed step-by-step instructions for your t:slim X2 pump and Insulin on Board.