One of the most persistent and damaging myths about Type 1 Diabetes is that exercise is dangerous for people with T1D. It is not. Exercise is one of the most powerful tools available for T1D management, and some of the world’s greatest athletes have T1D.
But exercise does interact with blood sugar in complex ways that require understanding and preparation. Here is what you need to know.
How Exercise Affects Blood Sugar
- Aerobic exercise such as running, cycling, and swimming generally lowers blood sugar by increasing insulin sensitivity and glucose uptake by muscles
- Anaerobic exercise such as weightlifting, sprinting, and HIIT can temporarily raise blood sugar by triggering stress hormone release
- Mixed exercise including team sports and circuit training can cause unpredictable swings in either direction
Before Exercise: Preparation
- Check your blood sugar before starting. A target starting range of 126 to 180 mg/dL is generally recommended for most aerobic exercise.
- If blood sugar is below 90 mg/dL, eat a small carbohydrate snack before beginning
- If blood sugar is above 270 mg/dL and you have ketones, postpone exercise until blood sugar comes down
- Reduce your basal insulin rate before exercise if using an insulin pump. Consult your endocrinologist for specific recommendations.
During Exercise
- Monitor blood sugar with a CGM and set low alerts to trigger early
- Keep fast-acting glucose such as glucose tablets, sports drinks, or gels accessible at all times
- For exercise lasting more than 60 minutes, plan for carbohydrate intake during activity
- Wear a medical ID so others know you have T1D if something goes wrong
After Exercise: The Delayed Effect
Exercise can continue to lower blood sugar for up to 24 hours after the activity ends, particularly overnight after afternoon or evening workouts.
- Check blood sugar more frequently in the hours after exercise
- Consider a small protein and carbohydrate snack after exercise to stabilize blood sugar
- Set a CGM alert to wake you if blood sugar drops overnight
T1D Athletes Who Inspire
People with T1D compete at the highest levels of sport. Jay Cutler played in the NFL for over a decade. Kris Freeman competed in four Olympic Games. Zippora Karz danced as a soloist with the New York City Ballet.
T1D does not limit athletic potential. It requires more preparation and more attention. But it does not set a ceiling on what you can achieve.
KFD’s Youth Ambassador Program connects young athletes with T1D to mentors who manage the same challenges. Find your community at koppfoundation.org.
