Fitness
Why blood sugar is high after exercise (and why that’s not always a bad thing)
By Gary Scheiner MS, CDCES
Published: Apr. 3, 2025
5 min read
The content in this article should not be taken as medical advice. Please consult with your healthcare provider regarding your individual health needs.
For years, we’ve all heard about the importance of exercise. With all the chatter and hype about the benefits of exercising, you decide it’s finally time to make health a habit. So, the next day, you get up early, chug some coffee, lace up your sneakers, and head out for a light jog. “This isn’t so bad,” you think to yourself as you make your way back home. Upon arrival, you take a quick glance at your Stelo Glucose Biosensor, and notice your glucose level increased from 135 mg/dL to 155 mg/dL.
How can that be? It turns out some forms of exercise can actually make blood sugar (or glucose) levels rise.
It’s a balancing act
Physical activity of any kind burns sugar (glucose) and helps the insulin that your body naturally produces work better. At any moment in time, there are multiple factors raising and lowering your glucose. Picture them on opposite sides of a balance scale:
Even though physical activity helps lower glucose, there may be other factors (e.g., food, stress hormones) that are raising it at the same time. If the factors raising glucose are stronger than the factors lowering it, the level goes up.
When we exercise, sometimes our bodies produce an increased amount of stress hormones. And eating shortly before exercise may also increase our blood sugar levels. Research has also shown that exercise performed in the early morning hours can result in a short-term glucose rise, because the body burns less sugar and more fat at that time of day.
Are glucose spikes during exercise bad for you?
Even if your glucose rises a little bit during exercise, it’s still important to remember physical activity comes with many health benefits. For one thing, the rise is usually temporary, and physical activity helps your insulin work better the rest of the day. Plus, burning calories and working on your physical health can improve long-term glucose management.
Which activities tend to elevate glucose levels?
Temporary blood sugar spikes tend to occur with high-intensity/short duration exercises and competitive sports. This is due to the stress hormone production or “adrenaline rush” that accompanies these kinds of activities. Examples include:
- Weightlifting (particularly when using high weight and low reps)
- Sports that involve intermittent “bursts” of activity like baseball, softball or golf
- Sprints in events such as running, swimming and rowing
- Events where performance is being judged, such as gymnastics or figure skating
- Sports activities in which winning is the primary objective
What can you do to prevent a glucose rise when exercising?
Anything that reduces the “adrenaline” rush during a workout will help keep glucose levels from going up. One approach is to perform a long warm-up and cool-down. This can look like the activity that you are already doing, but in a more relaxed form, for 5-10 minutes before and after your regular workout.
You can also practice relaxation techniques before stressful or intense activities. Examples include paced breathing, silent meditation, yoga, tai-chi, or simply doing something that you know relaxes you.
It is also a good idea to avoid eating large amounts of food before a workout—especially carbohydrates. Try sticking to water and small amounts of food (if any) before exercising. In addition to helping keep your glucose from going up, it will also help you to feel and perform your best.
It’s all about long-term benefits
The main thing to remember is that a temporary high blood sugar levels during exercise might seem confusing, but it’s not a bad thing—in fact, it’s completely normal. So, if you notice your glucose rising in connection with workouts, don’t be discouraged. The key is consistency. With tools like glucose biosensors, you can experiment with different types of physical activity and gain insights into your glucose trends. Sticking with an exercise routine will pay off in the long run, leading to better overall health and glucose stability. Keep moving, and trust that your body is benefiting in ways that go beyond your glucose numbers.
The production of this article was sponsored by Stelo by Dexcom.
Author profile
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Gary Scheiner MS, CDCES
Gary Scheiner is the owner and Clinical Director of Integrated Diabetes Services, a practice specializing in intensive insulin therapy and advanced education for children and adults throughout the world.