TABLE 1.

Carbohydrate Intake Strategies Based on Pre-Exercise Blood Glucose Level

Pre-Exercise Blood Glucose ConcentrationAction
<90 mg/dLIngest 15–30 g of fast-acting carbohydrates before the onset of exercise, depending on the size of the individual. Follow with extra carbs throughout exercise.
90–149 mg/dLStart consuming extra carbs at the onset of exercise (∼0.5–1.0 g/kg body mass/hour of exercise), depending on the energy expenditure and the amount of circulating insulin at the time of exercise.
150–249 mg/dLInitiate exercise and delay consumption of extra carbs until blood glucose levels drop to <150 mg/dL.
250–349 mg/dLTest for ketones: do not perform any exercise if moderate to large amounts of ketones are present (27); contact your health care team. Initiate mild- to moderate-intensity exercise. Intense exercise should be delayed until glucose levels drop to <250 mg/dL because intense exercise may exaggerate the hyperglycemia.
≥350 mg/dLTest for ketones: do not perform any exercise if moderate to large amounts of ketones are present (27); contact your health care team. If ketones are negative (or trace), consider conservative insulin correction (e.g., 50% correction) before exercise, depending on current “on board” (active) insulin status. Initiate mild to moderate exercise and avoid intense exercise (aerobic or anaerobic) until glucose levels drop.
  • Blood glucose concentrations should always be checked before exercise, and if glucose is dramatically elevated (≥350 mg/dL), the urine or blood should also be tested for ketones. The target range for blood glucose before exercise is 90–250 mg/dL. Carbohydrate intake should depend on the glucose concentration at the start of exercise. Regardless of their initial blood glucose concentration, patients should continue to monitor blood glucose regularly during exercise (every 30–45 minutes) using an accurate glucose meter and to adjust insulin and carbohydrate intake accordingly. In general, adjusting insulin doses before exercise will reduce the need for increased carbohydrate intake. Adapted from Refs. 26 and 27.