Type 1 Diabetes: Avoid Low Blood Sugar During Exercise

People with type 1 diabetes are at greater risk for hypoglycemia, or low blood sugar, when exercising. These tips can help you stay safe.

Amy Solomon
Reviewed by
Philip Levy, MD
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Of course you know exercise is an important part of your type 1 diabetes management plan. And if you’re making an effort to hit the track, the gym or the Zumba floor, kudos are definitely in order! But to get the most carefree enjoyment out of your activity, it’s key to guard against episodes of low blood sugar, also known as hypoglycemia. That’s because during exercise, the body gets energy by drawing blood sugar from the muscles and liver. As blood sugar stores get depleted, potentially dangerous lows can occur.

“All human beings need fuel when they exercise,” says Ginger Vieira, a personal trainer and yoga instructor from Burlington, VT, who’s been living with type 1 diabetes since 1999. "But in people with type 1 diabetes, it’s 10 times more complicated because we control the amount of fuel that’s available to our bodies through the insulin we take and the food that we eat."

But don’t let that keep you on the couch. Follow these tips for keeping blood sugar on an even keel while you get or stay in shape.

Fuel up before a workout. Pick faster-acting carbs like oatmeal, a banana or other fruit, a glass of juice, or sports gels (flavored carbohydrate gels in single-serving packets) for your pre-exercise snack. Stay away from fat-laden treats like ice cream because they take longer to digest.

How much should you eat before exercising? "Everyone’s needs are different," says Vieira. She recommends this pre-workout tip: "Eat 10 grams of carbohydrate [the amount in a half-cup of blueberries or five saltine crackers] and don’t take a bolus dose of insulin. See what your blood glucose is halfway through your workout. If your blood sugar levels are high, or over 160 mg/dL, you need fewer carbs; if you’re low, or less than 100 mg/dL, you need more."

Know the signs of low blood sugar. As you exercise, keep alert for signs of hypoglycemia, including dizziness, lightheadedness, exhaustion or trouble focusing. When you have low blood sugar during exercise, you need to stop and treat yourself," says Vieira. “That's why it’s so important to prepare—one low and you’ve screwed up your whole workout.”

Keep a snack on hand. Whether you’re at the gym or jogging in the park, always carry a portable snack or drink that can quickly raise blood sugar levels if necessary, like a juice box, glucose tabs or a candy that contains dextrose (Smarties or Pixy Stix).

Think of your body as a "diabetes science experiment,” Vieira says. “If you’re just getting into an exercise regimen, you need to check blood sugar at the beginning, middle and end of a workout,” she says. Then use that information to tailor your workout schedule and avoid future lows.

If you need more help, Vieira recommends finding a qualified exercise coach or personal trainer: “Someone to teach and support you is crucial.” Look for someone trained in sports nutrition and certified by the American College of Sports Medicine (ACSM) or another reputable organization like the American Council on Exercise.

July 2013