How to Prevent Hypoglycemia When You Exercise with Diabetes

Low blood sugar can be prevented (and shouldn’t stop you from hitting the gym).

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You already know that exercise is one of the most powerful tools for managing diabetes and its complications. In a 2015 study, regular exercise was associated with lower A1C levels, lower body weight, and improved cholesterol levels among patients with type 2 diabetes. And it doesn’t require daily gym sessions: A study in Diabetes Care found that resistance training just twice a week for four months reduced fasting blood glucose levels by 7.1 percent for older men with type 2 diabetes. Here’s more info about how exercise helps manage diabetes.

But a word of caution: If you have diabetes, there’s a chance that exercise may lower your body’s blood glucose levels too much. “It’s important [for patients] to monitor their blood sugar before, during, and after exercise,” says Joan Pagano, an exercise physiologist in New York City. “The danger is, as cells take up the blood sugar from the bloodstream, it can cause hypoglycemia or low blood sugar.”

Hypoglycemia may not affect all people with diabetes. Those who take insulin or oral medications known for lowering blood sugar are more at risk for low blood sugar during exercise, according to Minisha Sood, MD, an endocrinologist in New York City. “It’s important for them to check their blood sugar before exercise to make sure it’s not below 100,” says Dr. Sood.

That doesn’t mean taking insulin should stop you from reaping the benefits of exercise, though. “If you feel shaky or confused at any time, you should stop the exercise and have a snack,” says Pagano. Juice boxes are an easy way to introduce sugar to the body quickly, but other options include nuts, bananas, or glucose tablets. The American Diabetes association recommends having 15 to 20 grams of carbohydrates if your blood sugar falls below 100. (That’s about half a cup of juice.)

If you are prone to hypoglycemia, your doctor may recommend a glucagon pen, according to Sandra Arévalo, RDN, a spokesperson for the American Association of Diabetes Educators. If you start to feel like you may faint, the glucagon pen can quickly help bring glucose levels up to a healthy range.

Even if your numbers look A-OK at the end of your cycling class, it’s a good idea to keep an eye on them afterward, especially if you’ve changed or increased the intensity of your workout routine. Hypoglycemia can occur up to 12 hours after your workout, which experts call the “lag effect.” That’s because the body is working to replace your glycogen stores.

After exercising, keep monitoring your blood sugar and looking for symptoms of hypoglycemia—like shakiness, weakness, or blurred vision—for several hours.  (Learn more about the signs of hypoglycemia and hyperglycemia and how to treat them here.)

To manage blood sugar safely, here are essential tips for exercising with diabetes.