Before exercise: Check your blood sugar before your workout
Before you start a new fitness program, talk with your healthcare professional. Ask if it's OK to do the type of exercise you want to try, especially if you have type 1 diabetes.
Exercise can cause blood sugar to become too low in people who take insulin. Blood sugar that's too low is called hypoglycemia. The risk also applies to people with type 2 diabetes who take insulin or other medicines linked with lower blood sugar. Your healthcare professional can teach you how to balance your medicine with exercise and diet.
Ask your healthcare professional:
- How the activities you want to do might affect your blood sugar.
- When is the best time of day for you to exercise.
- How the diabetes medicines you take might affect your blood sugar as you become more active. Depending on your treatment, your healthcare professional may tell you to adjust your medicine dose or the food you eat before exercise.
For the best health benefits, adults should work up to at least 150 minutes a week of heart-pumping aerobic activity. The activity should be moderate to vigorous in intensity. Examples include:
- Fast walking or hiking.
- Lap swimming or a water aerobics class.
- Stair climbing.
- Basketball, tennis or other sports.
- Exercise classes.
Adults also should aim to do 2 to 3 strength-training activities per week. Give yourself at least a day to recover from a strength-training session.
Children and teens with diabetes should get at least 60 minutes of moderate to vigorous aerobic activity every day. They should do muscle- and bone-strengthening activities at least three days a week. Some examples of muscle-strengthening activities are games such as tug of war and exercises using body weight or resistance bands. Bone-strengthening activities include jumping rope and running.
When you talk with your healthcare professional about exercise, ask about your blood sugar testing needs. If you manage type 2 diabetes without medicines, you likely won't need to check your blood sugar before exercise.
But many people with diabetes do need to test their blood sugar levels before physical activity. If you take insulin or other medicines that can cause low blood sugar, test your blood sugar 15 to 30 minutes before exercising.
If you use a continuous glucose monitor to track your blood sugar, talk with your healthcare professional. You may be told to test your blood sugar with a finger stick before, during or after exercise. If you receive insulin through an automated insulin delivery system, talk with your healthcare professional about that. Ask how to keep your blood sugar in a healthy range for exercise. This is key if you usually don't notice symptoms when your blood sugar is low — a condition called hypoglycemia unawareness.
Do not exercise if you've needed help with recovering from serious low blood sugar in the past 24 hours.
Below are some general guidelines for blood sugar levels before exercise. The measurements are in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L).
- Lower than 90 mg/dL (5.0 mmol/L). Your blood sugar may be too low to exercise safely. Before you work out, have a small snack that includes 15 to 30 grams of carbohydrates. Some examples are fruit juice, fruit and crackers. Or take 10 to 20 grams of glucose products, which come in forms such as gels, powders and tablets. After you exercise, check your blood sugar again to find out if it's about 90 mg/dL.
- 90-124 mg/dL (5-6.9 mmol/L). Take 10 grams of glucose before you exercise.
- 126-180 mg/dL (7-10 mmol/L). You're ready to exercise. But be aware that blood sugar may rise if you do strength training. Blood sugar also may rise if you do short bursts of hard aerobic exercise known as high-intensity interval training.
- 182-270 mg/dL (10.2-15 mmol/L). It's okay to exercise. Be aware that blood sugar may rise if you do strength training or high-intensity interval training.
Over 270 mg/dL (15 mmol/L). This is a caution zone. Your blood sugar may be too high to exercise safely. Before you work out, test your urine for substances called ketones. The body makes ketones when it breaks down fat for energy. The presence of ketones suggests that your body doesn't have enough insulin to control your blood sugar.
If you exercise when you have a high level of ketones, you risk a dangerous health problem called ketoacidosis. Ketoacidosis can be life-threatening. It requires urgent treatment. Ketoacidosis can happen to anyone with diabetes, but it is much more common with type 1 diabetes. Instead of exercising right away if you have ketones, take steps to lower high blood sugar. Then wait to exercise until your ketone test shows an absence of ketones in your urine.
在运动期间，有时需要关注低血糖问题。如果您计划长时间运动，请每 30 分钟检查一次血糖水平，特别是当您尝试一项新的活动或增大锻炼强度或是持续进行锻炼时。每隔半小时左右检查一次，可以让您知道自己的血糖水平是稳定、上升还是下降，以及继续运动是否安全。
- 血糖为 70 mg/dL（3.9 mmol/L）或更低
吃或喝一些东西（含大约 15 克能够快速起效的碳水化合物）来提高血糖水平，例如：
- 1/2 杯（4 盎司/118 毫升）果汁
- 1/2 杯（4 盎司/118 毫升）常规（非无糖）软饮料
15 分钟后复查血糖。如果还是太低，再吃 15 克碳水化合物，15 分钟后再检测一次。
根据需要重复上述步骤，直到血糖达到至少 70 mg/dL（3.9 mmol/L）。如果您还没有完成训练，可以在血糖恢复到安全范围后继续训练。
您运动越激烈，您的血糖受影响的时间就越长。在运动之后，低血糖甚至可能会持续 4 到 8 个小时。锻炼后吃一些含有慢速碳水化合物的零食，例如格兰诺拉燕麦棒或什锦干果，可以帮助防止血糖下降。
如果运动后确实出现低血糖，请吃少量含碳水化合物的零食，例如水果、饼干或葡萄糖片，或喝半杯（4 盎司/118 毫升）果汁。
Jan. 20, 2022
- Grant RW, et al. Standards of medical care in diabetes —2018. Diabetes Care. 2018;41:S1.
- McCulloch DK. Effects of exercise in diabetes mellitus in adults. https://www.uptodate.com/contents/search. Accessed Nov. 9, 2018.
- Diabetes diet, eating and physical activity. National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/diabetes/overview/diet-eating-physical-activity. Accessed Nov. 9, 2018.
- Physical Activity Guidelines for Americans. 2nd ed. U.S. Department of Health and Human Services. https://health.gov/paguidelines/second-edition. Accessed Nov. 12, 2018.
- Hypoglycemia (Low blood glucose). American Diabetes Association. http://www.diabetes.org/living-with-diabetes/treatment-and-care/blood-glucose-control/hypoglycemia-low-blood.html. Accessed Nov. 9, 2018.