Question:
Why does blood sugar level go up after exercise?
Blood sugar can sometimes go up after exercise because exercise is not only a “sugar-burning” activity. Intense exercise can act like physical stress on the body.
During hard exercise, your body may release stress hormones such as adrenaline and cortisol. These hormones tell the liver to release stored glucose into the blood so your muscles have enough energy.
If the liver releases more glucose than your body can use or match with insulin, your blood sugar may rise temporarily.
Answer by Dr. Albana Greca, MD, MMedSc
Hello,
This is a common question. Many people expect exercise to always lower blood sugar, but the body’s response depends on the type of exercise, starting blood sugar level, insulin level, food intake, stress, hydration, and diabetes medication.
When you exercise intensely, your muscles need quick energy. To help, the liver releases stored glucose into the blood. At the same time, stress hormones may rise and temporarily push blood sugar higher.
This is more likely with:
You can compare your readings with this guide: blood sugar levels by time of day.
Moderate exercise, such as walking after meals, usually helps the muscles use glucose from the blood. This is why many people notice lower blood sugar after walking, gentle cycling, gardening, or light housework.
If your blood sugar rises after intense exercise, compare it with a lighter activity such as a 15- to 30-minute walk, if your doctor says exercise is safe for you.
Be careful. If your blood sugar is very high, exercise may not always be safe, especially if ketones are present.
If your blood sugar is above 240–250 mg/dL, ask your healthcare provider whether you should check urine or blood ketones before exercise. If ketones are present, avoid vigorous exercise and follow your diabetes sick-day or high-glucose plan.
Read more here: dangerous blood sugar levels.
You may also find this helpful: diabetes and exercise.
If your blood sugar is very high, you feel sick, you are vomiting, you are dehydrated, or you have moderate or large ketones, do not exercise to “burn off” the sugar. Contact your doctor or seek urgent medical care according to your diabetes plan.
A temporary rise in blood sugar after intense exercise can happen. The best way to understand your own pattern is to check before and after exercise and keep a simple log. If your readings are repeatedly high after exercise, or if you use insulin, speak with your diabetes care team before adjusting food, insulin, or medication.
Educational safety note: This answer is for general diabetes education only. It does not replace personal medical advice, diagnosis, or treatment. Do not change diabetes medication, insulin dose, or exercise intensity without speaking with your healthcare provider.
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