Exercise Guidelines

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Benefits of Exercise 

Female friends in exercise class
  • Sharpens the mind and tones the body 
  • Helps control stress and improves mood and overall well-being  
  • Aids in weight management and weight loss
  • Improves blood pressure and cholesterol levels 
  • Increases insulin sensitivity and lowers blood glucose 


Factors that may affect your blood glucose during exercise include

  • How fit you are – Less fit? Blood glucose can drop quickly.  
  • Type of exercise – Anaerobic exercise may raise blood glucose initially. Aerobic is more likely to have an immediate effect on lowering blood glucose
  • Insulin on board (IOB) – The more medication/ insulin on board the more likely you are to go low. Not enough medication may result in high blood glucose
  • When and what foods were last eaten 
  • Temperature and humidity – Hot?  Blood vessels can dilate and blood glucose may drop. 
  • Hydration status – Dehydrated? Your blood glucose may rise. 
  • Current blood glucose
  • Time of day – Insulin sensitivity changes during the day: Less sensitive early in the day—you may need to “break-the-fast,” but take less medication with food; more sensitive in the afternoon and evening, which may increase your risk of hypoglycemia.  

*Everyone’s response to physical activity is different!


Glucose Metabolism and Exercise 

A couple women walking

In individuals without diabetes

  • Insulin output by the pancreas decreases to compensate for decreased needs in the body. 
  • Exercise activates non-insulin dependent glucose transport into muscle cells 
  • As insulin levels decrease, counter-regulatory hormones cause the liver to release glucose to keep blood glucose stable 

In individuals with diabetes, 

  • Injected insulin and other diabetes medications impact glucose metabolism in exercise.
  • Circulating insulin levels do not decrease but muscles take in more glucose and any insulin present becomes more efficient in its ability to lower glucose.
  • High insulin levels impair glucose release from the liver and may cause hypoglycemia. 
  • Peak performance occurs when insulin levels and fuel available for energy are balanced, keeping blood glucose in a normal range 


Exercise Tips 

  • Check your blood glucose 15-30 minutes before exercise, and every 30 minutes to 1 hour during exercise. 
  • If taking insulin, check your Insulin-on-Board (IOB) before starting exercise. It may help to decide whether you need a snack to prevent hypoglycemia. The more insulin you have on board, the higher the likelihood of a low glucose.  You may require more carbohydrates prior to exercise.  
  • If your blood glucose is higher than 250 mg/dl, exercise may be detrimental. Review exercise glucose targets with your endocrinologist or diabetes team.
  • If your blood glucose is less than 100 mg/dl, consider eating a snack without insulin or oral medication before you exercise. Monitor your blood glucose every 30 minutes to 1 hour during activity.  Review safety measures with your endocrinologist or diabetes team.
  • Exercise with a friend or in a group if you are new to exercising. 
  • Keep your meter accessible. Glucose monitoring with a continuous glucose monitoring (CGM) helps to assess trends and can guide decision making. 
  • Carry fast-acting carbohydrates with you to treat unexpected low blood glucose.  
  • Drink plenty of water to prevent dehydration. Have fluids available during activity. Consider having Gatorade with you for a carbohydrate replacement while exercising. 
  • Consider adjusting your oral medication or insulin prior to exercise. You may need to decrease your mealtime dose/bolus or use a temporary basal rate (via insulin pump) while exercising. 
  • Consult your diabetes team to provide specific recommendations for treatment surrounding exercise and diabetes.


Preventing hypoglycemia during exercise

Summer health

Consult your diabetes team for specific recommendations for treatment surrounding exercise and diabetes. The following are steps that may reduce the risk of hypoglycemia during exercise:

  • Eat a snack with carbohydrates (and protein) one hour prior to exercise if needed. Consider omitting or reducing the oral medication dose/insulin bolus.
  • If on an insulin pump, check your insulin-on-board (IOB). If taking multiple daily insulin injections (MDI), start using a phone app that can help determine how much insulin you have on board. If you have active insulin remaining from a previous bolus, consider eating a larger snack.
  • In some circumstances, it is recommended to eat 15-30 grams of carbohydrate for every 30 minutes to 1 hour of exercise. Energy drinks, energy gels and shot blocks are all good options.

Blood Glucose Recommendations for Carbohydrate Intake

Before exercise:

  • BG less than 80 mg/dl: Eat a minimum of 30 grams of carbohydrates and wait 15 minutes prior to exercising.
  • BG 80-180 mg/dl: Eat 15-30 grams of carbohydrate
  • BG greater than 180 mg/dl: You may not need a snack

Remember that complex carbohydrate turns to glucose in 1-2 hours, protein in 3-4 hours and fat extends the effect. Consume one hour prior to exercise for 30 minutes of exercise. For more than 30 minutes, increase snack to 30 grams of carb.

Examples of 15-30 g Carbohydrate Snacks:

  • 1 small banana or apple with 1-2 T peanut butter
  • 1 oz. nuts with 2 T dried fruit
  • 4-5 peanut butter crackers or crackers with cheese
  • ½ sandwich
  • Trail mix — 1/2 cup cereal, 1 T dried fruit, ¼ cup nuts
  • 1 granola bar (Luna, Nature Valley, Gnu, Lara, Kind )
  • 1 cup light yogurt with nuts or 1 cup plain yogurt with dried fruit

Preventing post-exercise hypoglycemia

  • Check blood glucose every 1-2 hours post-exercise.
  • There are two peaks of increased glucose requirements after exercise:
    • Approximately 60-90 minutes post-exercise, glycogen stores are being replenished and there is increased insulin sensitivity.
    • Additionally, there may be a change in metabolic rate and reduction in insulin requirements for up to 24 hours.

Combatting the first wave of hypoglycemia

  • Eat a carbohydrate snack or drink following exercise (trial 15-30 grams but this may need to be adjusted).
  • Reduce your basal rate following exercise for 1-2 hours.

Combatting the second wave of hypoglycemia

  • Reduce your oral medication/basal insulin dose:
    • If using MDI, decrease long-acting insulin dose
    • If using a pump, set a temporary basal rate to reduce overnight basal rates.

Review specific recommendations with your diabetes team prior to adjusting carbohydrate intake and medication/insulin dosing.

*Effects of exercise can last as long as 24-48 hours. To recover glycogen stores eat a balance of complex carbohydrates, protein and fat.