What moves your glucose
Why Did My Blood Sugar Go Up After Exercise?
Most exercise lowers blood sugar. Some doesn’t. The American Diabetes Association says heavy weightlifting, sprints and competitive sports can raise it, because they trigger stress hormones such as adrenaline.
On this page
Why exercise usually lowers glucose
According to the ADA, working out usually makes blood sugar dip. Using your muscles helps burn glucose and improves the way insulin works. That is why most aerobic exercise lowers glucose.
Why some exercise raises it
- Adrenaline. Heavy weightlifting, sprints and competitive sports trigger stress hormones. The ADA explains that adrenaline raises glucose by stimulating your liver to release glucose.
- Carbohydrate before the workout. Eating a lot of carbohydrate beforehand can push glucose above your target range, even if the workout itself is vigorous.
- Time of day. The natural early-morning rise known as the dawn phenomenon, between about 4 and 8 a.m., can lead to higher readings during morning workouts. The same workout later in the day is less likely to cause a rise.
It can rise after exercise, not only during it
The ADA notes that you might see your glucose go up after exercise as well as during it. The page doesn’t say how long a post-exercise rise lasts, and that is one reason a CGM trace of the hours afterward is more informative than a single reading.
Finding your own pattern
The ADA’s takeaway is to check glucose regularly and keep a workout log to learn your personal patterns. Dia imports workouts from Apple Health and shows the glucose graph around each one, so you can compare how a similar session played out on different days. It describes what it sees and doesn’t tell you what to change.
The ADA page also discusses asking your doctor about adjusting rapid-acting insulin or other medication before workouts that tend to raise glucose. That is a decision for you and your care team.
Questions
Does exercise always lower blood sugar?
No. The ADA says most aerobic exercise lowers glucose, but high-intensity training and weightlifting can raise it.
Can a morning workout raise blood sugar?
It can. The ADA notes that the dawn phenomenon, a natural rise between about 4 and 8 a.m., can lead to higher readings during morning workouts.
What does the ADA suggest if workouts keep raising glucose?
It suggests moderate-intensity aerobic exercise or circuit training with light weights and high repetitions, relaxation techniques such as paced breathing, and trying a later time of day if you usually exercise early. It also suggests asking your doctor about medication before workouts that often raise glucose.