07/20/2026
Why did my glucose go UP during one workout but DOWN during another? This is a common question we get.
This is my glucose readings using a Lingo CGM.
On day 1, I ate a breakfast of grits, egg whites, and chicken sausage. About 90 minutes later, I started a 1 hour 45 minute tennis match in 90ยฐF heat. Instead of dropping, my glucose gradually rose to around 125 mg/dL before slowly returning toward baseline.
On day 2, I drank half of a high-protein smoothie (protein powder, collagen, flax, chia, powdered peanut butter, cocoa, and oats) before a 20-minute high-intensity rowing session. This time, my glucose fell to 74 mg/dL.
So what changed? Exercise doesn't always lower glucose.
The type, intensity, duration, and environment all influence your glucose response.
Competitive exercise, especially in the heat, triggers the release of stress hormones like adrenaline, noradrenaline, and cortisol. These hormones signal your liver to release stored glucose into the bloodstream to fuel working muscles. If you ate carbs (which you should if you want to fuel your body to perform) that will also influence glucose.
Steady, whole-body exercise like rowing tells a different story. Large muscles (such as legs +glutes + back) rapidly pull glucose from the bloodstream to refuel energy stores, often faster than the glucose entering from a small meal/snack. The result can be a drop in glucose despite eating beforehand.
The takeaway?
A glucose rise during exercise isn't automatically "bad," and a glucose drop isn't automatically "better." Both can be normal physiological responses depending on what your body is trying to do.
Instead of judging a single glucose value, consider:
What you ate
When you ate
The type and intensity of exercise
Environmental conditions (like heat)
How quickly your glucose returns to baseline
CGMs don't just show us numbersโthey help us understand the remarkable ways our bodies adapt to different metabolic
