Low Blood Sugar During Sports Practice: Diabetes Questions & Answers

Q: My son is a high school athlete who uses a pump and CGM (continuous glucose monitor). We don’t have any blood sugar problems when he works out before school, but he keeps dropping low during his afternoon practices. He removes his pump and has a big snack right beforehand but still drops 100 to 150 mg/dl. It’s driving us both nuts! Do you have any recommendations for preventing low blood sugar during sports?

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A: I see this a lot. Early-morning exercise tends to cause less of a blood sugar drop than the same workouts performed later in the day. Exercising one to three hours after a meal such as lunch can be a real challenge because the bolus insulin still packs a pretty significant punch. But don’t give up. Here are some strategies that should help:

1. Try reducing the bolus given at lunch (so that there is less insulin working during the afternoon workout), and choose lunch foods that are slow to digest, such as dairy products, high-fiber foods, legumes, fresh vegetables, whole fruits and healthy fats. Slowly digesting foods are good for preventing a sharp blood sugar spike after lunch and should provide a steady source of glucose during the workout.

2. Take rapid-acting carbs (in liquid form if possible) without a bolus 15 to 30 minutes BEFORE the workout. Food consumed right before exercising may sit in the stomach and not digest until the workout is over.

3. Consider setting a temporary basal rate reduction on the pump. Ideally, reduce the basal by 60% to 80% for a couple of hours, starting 90 minutes before the workout. That way, there will be less basal insulin working during the exercise session.

Want to learn more about sports with type 1 diabetes? Read “Helping a Student Athlete With Type 1 Diabetes.”

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