About Exercise Glucose Spikes

Exercise can sometimes cause glucose to rise temporarily, even though activity is generally beneficial.

Glucose spikes during exercise: should you be concerned?

If you’re tracking glucose with a Stelo biosensor or a continuous glucose monitor (CGM), it can be surprising to see glucose rise during high-intensity exercise. In most cases, this is not a cause for concern.

During intense exertion, stress hormones can signal the liver to release stored glycogen into the bloodstream and produce additional glucose to fuel a “fight or flight” response. This rise can indicate you’re mobilizing stored glycogen, meaning the workout is intense enough that the body can’t rely primarily on fat and needs to use glucose as fuel.

Exercise-related rises are different from food-related spikes. Over time, high-intensity training can improve fasting glucose and insulin sensitivity. These adaptations support better metabolic flexibility and overall glucose control.

To learn more about exercise and metabolic fitness, read our blog post here.

Removing exercise spikes from your Levels score

When you log an activity as Strenuous, that log and any other logs created within 2 hours won’t impact your Stability Score.

If you don’t want exercise-related spikes to affect your Levels scores, follow the steps on How to Log Strenuous Exercise.

Logging the activity as Strenuous should prevent your workout from negatively impacting your day’s score.

Automatic strenuous detection

If your exercise is imported from Apple Health or Health Connect, it will automatically be marked as Strenuous if your heart rate goes above 150 BPM. This corresponds to 85% of a presumed max heart rate of 177.

If you have an unusually low max heart rate and your strenuous activity isn’t being captured, you can adjust the max heart rate threshold by following the steps on How to Adjust Your Max Heart Rate Threshold.