Your Loop has two override targets that you can set; Pre-meal and Workout. When activated, these targets will "override" or take the place of your usual correction range and therefore will affect Loop's decisions about insulin delivery.
You can set the value for these override targets from the Correction Range area of Loop settings. Generally speaking, pre-meal targets are set to value(s) lower than your correction range and workout targets are set to value(s) greater than your correction range. Loop will indicate that an override target is active by showing a darker blue bar on the blood glucose chart showing the duration and loation of the target.
The pre-meal target, when activated by pressing on the icon, will stay active for:
- one hour, or
- until carbs are entered, or
- until pre-meal target is manually cancelled by pressing the icon again.
Pre-meal target will automatically end when one of those three things happens, whichever comes first will end the pre-meal target.
The original intent of the pre-meal target was to help give a gentle, easy pre-bolus effect to help lessen a post-meal blood glucose spike. By lowering your Loop's target going into a meal, you can get a "pre-bolus" effect because Loop will aim for that lower target and thus tend to set a little more aggressive insulin delivery while the target is active. Loop will recognize the "extra" insulin that has been delivered while pre-meal is active, and Loop will smartly take that into account when it is finally time to recommend a bolus at meal entry time.
Pre-meal target won't replace the utility of a true pre-bolus in most situations, but it can be useful in many situations beyond simply helping meals. This lower target can help Loop be more aggressive:
- During stressful events where adrenaline might be causing increased blood glucose
- During exercise that may tend to increase blood glucose
- During illness that is causing high blood glucose
The workout target, when activated, will give a duration choice of 1 hour, 2 hours, or indefinitely. The workout target, set greater than your usual correction range, is useful to help in situations where Loop needs to be less aggressive with insulin delivery. The most common use of the workout target is to set it in advance and during exercise to help minimize IOB going into a workout. While the name is a hint to the most common timing of this override's use, there are other times where it can be helpful such as:
- Helping to recover from low blood glucose treatment
- Helping after workouts when still experiencing increased insulin sensitivity
- Helping during illness which is tending to lower blood glucose or increase insulin sensitivity
You can read more about the timing and use of workut targets before/during/after exercise in the Exercise page of these tips.