During exercise: Watch for symptoms of low blood sugar

During exercise, low blood sugar is sometimes a concern. If you're planning a long workout, check your blood sugar every 30 minutes — especially if you're trying a new activity or increasing the intensity or duration of your workout. Checking every half-hour or so lets you know if your blood sugar level is stable, rising or falling, and whether it's safe to keep exercising.

This may be difficult if you're participating in outdoor activities or sports. However, this precaution is necessary until you know how your blood sugar responds to changes in your exercise habits.

Stop exercising if:

  • Your blood sugar is 70 mg/dL (3.9 mmol/L) or lower
  • You feel shaky, weak or confused

Eat or drink something (with approximately 15 to 20 grams of fast-acting carbohydrate) to raise your blood sugar level, such as:

  • Glucose tablets or gel (check the label to see how many grams of carbohydrate these contain)
  • 1/2 cup (4 ounces/118 milliliters) of fruit juice
  • 1/2 cup (4 ounces/118 milliliters) of regular (NON-diet) soft drink
  • Hard candy, jelly beans or candy corn (check the label to see how many grams of carbohydrate these contain)

Recheck your blood sugar 15 minutes later. If it's still too low, have another 15 gram carbohydrate serving and test again 15 minutes later.

Repeat as needed until your blood sugar reaches at least 70 mg/dL (3.9 mmol/L). If you haven't finished your workout, you can continue once your blood sugar returns to a safe range.

After exercise: Check your blood sugar again

Check your blood sugar as soon as you finish exercising and again several times during the next few hours. Exercise draws on reserve sugar stored in your muscles and liver. As your body rebuilds these stores, it takes sugar from your blood.

The more strenuous your workout, the longer your blood sugar will be affected. Low blood sugar is possible even four to eight hours after exercise. Having a snack with slower-acting carbohydrates, such as a granola bar or trail mix, after your workout can help prevent a drop in your blood sugar.

If you do have low blood sugar after exercise, eat a small carbohydrate-containing snack, such as fruit, crackers or glucose tablets, or drink a half-cup (4 ounces/118 milliliters) of fruit juice.

Exercise is beneficial to your health in many ways, but if you have diabetes, testing your blood sugar before, during and after exercise may be just as important as the exercise itself.

Dec. 01, 2015 See more In-depth