Is it correct that blood sugar rises when exercising?

Regular exercise is essential for patients with diabetes. However, there are occasional reports of blood sugar levels rising after exercise. A reader who was concerned about blood sugar increasing after exercise sent a question.

Is it okay to continue exercising even if my blood sugar rises during exercise? I'm also curious whether the increased blood sugar from exercise has any negative effects on health.

Q. Is it okay for blood sugar to rise after exercise?

A. I need to check how much the blood sugar rises.

When we exercise, our bodies secrete a lot of hormones that raise blood sugar levels. Mainly glucagon, cortisol, and catecholamines are released. These hormones stimulate the liver to produce more glucose during exercise to prevent blood sugar from dropping sharply. If the amount of sugar produced by hormonal action exceeds the amount consumed by muscles, blood sugar levels rise. However, after exercise ends, these hormones naturally decrease, and as muscles begin to consume glucose again, blood sugar levels return to normal, so there is no need to worry.

Thus, blood sugar changes caused by exercise are natural and temporary, but it is necessary to check whether the extent of these changes is not excessive, depending on the intensity and effectiveness of one's exercise.

Typically, exercising at low to moderate intensity causes an immediate decrease in blood sugar levels, while high-intensity exercise causes blood sugar to rise initially and then start to decrease after one or two hours. Measure your blood sugar once just before exercise and again 30 minutes after starting. If the blood sugar level 30 minutes after exercise is more than 100 points higher than before exercise, it indicates that the exercise intensity was too high, causing a rapid spike in blood sugar. Although blood sugar may eventually decrease on its own afterward, it is better to avoid sudden fluctuations in blood sugar. Therefore, it is recommended to either reduce the exercise intensity or slightly increase the pre-exercise meal portion to improve the situation.

It is also good to check your blood sugar once an hour after starting exercise. If your blood sugar drops below 70, you should try to reduce the intensity of your exercise or consume a snack before exercising to prevent hypoglycemia.

In summary, the natural blood sugar changes caused by exercise are: ▲30 minutes after starting exercise, blood sugar levels decrease or, if they increase, the rise should be less than 100; and ▲one hour after exercise, blood sugar should be at least 70.

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Lately, I have been noticing.

Before exercise. After exercise. Before meal. After meal.

It seems like they check everything before and after snacks.

For people with diabetes, checking after exercise is important.