Expert Q&A

Diabetes & Exercise: Why Do You Get a Higher Blood Sugar Reading after Working Out?

Why do I sometimes get a higher blood sugar reading after exercise?

-Mary from Massachusetts

When you exercise, your muscles need sugar to supply energy, so the liver increases the amount of sugar it releases into the bloodstream. In order for your muscles to be able to use sugars, they need insulin to ‘unlock' the cells and let the sugars in. If you do not have enough insulin available, your blood sugar levels will increase. High blood sugar, or hyperglycemia, after exercise is caused by either:

  • Insulin deficiency
  • Increase in counter-regulatory hormones.

To exercise safely, consult your physician before starting any exercise program. Also, check your blood sugar before and after working out. Do not exercise if you have ketones and your blood sugar is over 250mg/dl.

Cindy Guirino, RD/LD, CDE, CNSD, ACE PT
Contributing Expert

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