Blood Glucose Control and Exercise

There are a few ways that exercise lowers blood glucose:

  • Insulin sensitivity is increased, so your cells are better able to use any available insulin to take up glucose during and after activity.
  • When your muscles contract during activity, it stimulates another mechanism that is completely separate of insulin. This mechanism allows your cells to take up glucose and use it for energy whether insulin is available or not.

This is how exercise can help lower blood glucose in the short term. And when you are active on a regular basis, it can also lower your A1C.

Understanding Your Blood Glucose Reaction

The affect physical activity has on your blood glucose will vary depending on how long you are active and many other factors.  Physical activity can lower your blood glucose up to 24 hours or more after your work out by making your body more sensitive to insulin.

You should become familiar with how your blood glucose responds to exercise. Checking your blood glucose level frequently before and after exercise can help you see the benefits of activity. You also can use the results of your blood glucose checks to see how your body to reacts to different activities. Understanding these patterns can help you prevent your blood glucose from going too high or too low.

Hypoglycemia and Physical Activity

Everyone with diabetes should be prepared to treat hypoglycemia, but people with type 1 are at the highest risk for hypoglycemia. People with type 2 are less likely to have issues with hypoglycemia during or after exercise, unless they are on insulin or an insulin secretagogue.

If you experience hypoglycemia during or after exercise, treat it immediately. Use the same process as you would any other time of the day:

  1. Have at least 15-20 grams of fast-acting carbohydrate (sports drinks, regular soda, or glucose tabs are all good ideas). 
  2. Wait 15-20 minutes and check your blood glucose again.
  3. If it is still low and your symptoms of hypoglycemia don't go away, repeat the treatment.
  4. After you feel better, be sure to eat regular meals and snacks as planned to keep your blood glucose level up.

If you want to continue your workout, you will usually need to take a break to treat your low blood glucose, depending on what activity you are doing and how much insulin you have circulating in your bloodstream. If you do stop exercising, check to make sure your blood glucose has come back up above 100 mg/dl before starting to exercise again.

Keep in mind that low blood glucose can occur during or long after physical activity. It is more likely to occur if you:

  • Take insulin or an insulin secretagogue
  • Skip a meal or don’t eat something within 30 minutes to two hours after stopping
  • Exercise for a long time
  • Exercise strenuously

If hypoglycemia regularly interferes with your exercise routine, talk to your healthcare provider about adjusting your treatment plan. Your provider may suggest eating a small snack before you exercise or they may make an adjustment to your medication(s). For people engaging in long duration exercise, a combination of these two regimen changes is usually necessary to prevent hypoglycemia during and after exercise.

How Does Food Fit into It All?

Most people do not need to add extra carbohydrates to their meal plan unless they are exercising for more than an hour at a time. For those who are trying to lose weight, adding extra food to your meal plan may actually cancel out the calories burned during exercise.

To maximize your energy for activity, it is important to stick to your usual meal plan. Focus on making healthy choices and filling your plate with a balance of non-starchy vegetables, fruit, whole grains, low- or non-fat dairy, healthy fats, and lean meats.

To learn more about the best choices, visit "What Can I Eat?"

  • Last Reviewed: September 4, 2013
  • Last Edited: December 16, 2013

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