Blood Sugar and Physical Activity

By: Catherine G., RDN, LD


Being active is an important part of healthy living. It improves mood and quality of life. It can help lower weight, blood pressure, anxiety, and blood sugar. However, blood sugar can change based on the timing and type of activity.

Exercise Can Lower Blood Sugar in the Short and Long Term

Most of the time, our bodies need insulin to bring blood sugar into the muscle and create energy. During physical activity muscles can absorb blood sugar without insulin, causing a decrease in blood sugar. 

Being active any time during your day is beneficial. Timing activity 30 minutes to 3 hours after a meal can help decrease a blood sugar spike. Being active also has a positive impact on blood sugar levels for up to 24 hours after a workout. Because of this, exercising regularly will give you the biggest benefit.

Sometimes Exercise Can Raise Blood Sugar

This happens mostly during short intervals of high intensity exercise. Examples include weightlifting, sprinting, high intensity interval training (HIIT), or spinning classes.

During these intense movements, the muscles and brain need access to quick energy from blood sugar. So, the body releases more into the blood. However, since it is being absorbed by the muscle, the blood sugar will come back down.

Things to Keep in Mind

If you take insulin or sulfonylureas, you are at higher risk for having low blood sugar. Other diabetes medications, like Metformin, have little to no risk of low blood sugar. Here are some suggestions to lower your risk of low blood sugar: 

  • Talk to your health care provider about any precautions you should take before starting a new exercise plan. 
  • Check your blood sugar before and after being active. Risk of low blood sugar can happen anytime between 6-12 hours after a workout.
  • If you are active after dinner, watch blood sugar trends before going to bed to prevent low levels during the night.
  • During exercise carry a fast-acting carb, like glucose tabs, in case your blood sugar goes low. 
  • Stay hydrated. 

Be sure to talk to your healthcare provider and dietitian before making any changes to your routine.

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