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During Exercise

exercise and diabetes: the balancing act

In previous levels and articles we’ve talked about the fact that sometimes exercise raises blood glucose, 
sometimes it lowers it; sometimes your child will need extra carbs before physical activity, sometimes after the activity, sometimes before, during and after; sometimes they may even need insulin during an activity. Discouraged yet? Don’t be! Your child will engage in some type of activity that’s just part of being a kid. Balancing blood glucose and exercise is manageable. There are a few strategies you can use to help make exercise more fun and less stressful.

Strategies to Use During Exercise to Help Prevent Lows:

1.  One Gram per Kilogram per Hour (suggested by Dr. Michael Riddell1)

This first (and our favourite) strategy recommends using 1 gram (g) of carbohydrates for each kilogram (kg) of body weight for each hour of moderate to intense exercise

Example 1: If your child weighs 20 kg, you would give her 20g of carbs for each hour of exercise. Broken down, that would be 10g every half hour, or 5g every 15 minutes. 

Example 2: A child who weighs 32 kg may need 32g of extra carbs for an hour of moderate to intense physical activity (equivalent to 16g every half hour or 8g every 15 minutes).

This formula provides an educated starting point for how many extra carbs your child may need for exercise. Try it out and assess the result to see if your child needs this amount of extra carbs, more or less. If, as in example 2 above, your child is consuming 8g of extra carbs every 15 minutes during exercise and is still experiencing lows, perhaps she needs 10g every 15 minutes for that activity. Alternately, if she is consuming 8g of extra carbs every 15 minutes during exercise and her blood glucose is high following the activity, you could try 6g every 15 minutes for that activity.

Note: It’s preferable to provide the extra carbs throughout the activity (in 15-30 min increments) rather than in a “lump sum” pre-exercise, to avoid the substantial increase in blood glucose which may happen if your child consumes too many carbs before the activity starts. High blood glucose during the activity may impact how she feels and her ability to perform athletically. 

tips from the trenches of type 1 diabetes
When my son wants to participate in a spontaneous activity (such as jumping on the trampoline, riding his skateboard, etc) he knows to grab extra carbs for the time period that he plans to be doing that activity for. If he usually jumps for ½ an hour with his friends on the trampoline then he’ll grab 22 extra carbs (he weighs 45 kg) as he’s running out the door. He also makes sure that the carbs are fast-acting or high glycemic ( examples would be non-fat candy, white bread, pretzels, sports drinks, etc). That way his body will have those extra carbs available right away when he needs them. If he were to have something that’s slow-acting or low glycemic (like ½ of a cheese sandwich on whole grain bread or high fat ice cream) then the food would take too long to digest and he would probably have a low during exercise. For more information see Choosing the Right Carb for the Jobsection below. 


2.  Carbohydrate Replacement per 60 Minutes of Physical Activity table (Appendix D found at the back of Gary Scheiner’s book “Think Like a Pancreas")

The second strategy involves giving extra carbs for every 60 minutes of a given activity, as indicated in a table of values (which is broken down by body weight). 

Example 1: If your child weighs 23 kg, and is about to play soccer (practice), you would give her 13-17g of extra carbs for every hour she plays.

Example 2: A 45 kg child who wants to go biking at a moderate pace, will need to consume 24-30g of extra carbs for every hour that he exercises.

This strategy does account for the different levels of intensity involved in different physical activities. However, not every activity is listed in the table, which limits its applicability.

Making a choice with type one diabetes and exercise

Extra Carbs or Less Insulin?

Once you have used one of the above strategies to calculate the approximate amount of extra carbs your child needs for a given activity, you may either:

  • Give extra food (as described above), OR
  • Give less insulin

In the latter case, if an activity is planned immediately following a meal, instead of your child eating even more food after the meal, you may choose to subtract the insulin equivalent to the extra carbs from that bolus for that meal. For example, if your 40 Kg child wants to go tobogganing after supper, you could subtract insulin equivalent to 40 carbs (which would cover 1 hour of exercise) from the supper insulin. If she eats 60 carbs, you would only give insulin for 20 carbs instead of the full 60.  

Important Notes:

  • Giving less insulin only works if an activity is planned immediately (within 60-90 minutes) following a meal otherwise you will need to give extra carbs (this prevents a very high pre-activity blood sugar). 
  • Only cover a maximum of 1 hour of exercise using this method – anything more is likely to lead to high blood glucose.
  • Remember, your body needs a certain amount of insulin present to avoid ketones so decreasing the background insulin by more than 50% is not advisable.
  • This strategy of giving less insulin works for any meal of the day for individuals who are on a basal-bolus or pump program. For individuals who are NOT on a basal-bolus or pump program (i.e. use a peaking insulin, such as N/NPH) this strategy will not work at lunchtime. Your child will require extra carbs for activity during this time to prevent a low.
  • TALK TO YOUR CHILD’S DIABETES HEALTH CARE TEAM for guidance on adjusting carbs and/or insulin for exercise.

Choosing the Right Carb for the Job

choosing the right carb for exercise with type 1 diabetes
In addition to choosing the right amount of extra carbs, it is also important to be aware of the type of extra carb you use to manage exercise. A food’s Glycemic Index (GI) indicates how quickly it is digested – and, as a result, how quickly it raises blood glucose. High GI foods are broken down quickly, resulting in a fast rise in blood glucose; lower GI foods are broken down more slowly, resulting in a more moderate and longer-lasting rise in blood glucose.

If your child is participating in spontaneous activity for which you had little advance notice (for example, little ones running around the house, or older ones rushing out for an impromptu bike ride), a quick-acting (high GI) carb (similar to what you would use to treat a low), consumed immediately before or during the activity, may be necessary to avoid a low. This type of carbohydrate starts working very quickly. It is also used up very quickly, so your child will have to consume high GI foods often throughout the activity.

If, on the other hand, your child is participating in a planned activity, it may be beneficial to give a slower-acting (medium GI) carb (like fruit and yogurt, or a whole-grain granola bar) 60-90 minutes prior to the activity. This is an option if you are subtracting carbs from a meal pre-activity and you don’t want the blood sugar to spike too high but want the food to be available for the body to use during exercise. You may still need to give high GI foods throughout the activity to prevent a low. 
If you check your child’s blood glucose during an activity and he is on the lower side, it may be wise to choose a high GI carb (a sports drink, for example) for extra carbs to prevent a low.

See Nutrition/Glycemic Index for more information on different types of carbs.


1Type 1 Diabetes and Aerobic Exercise: Strategies for Optimal Glycemic Control”. Katherine E. Iscoe, BA, Bruce A. Perkins, MD MPH FRCPC, Michael C. Riddell, PhD.

Robertson K, Adolfsson P, Riddell M, Scheiner G, Hanas R.  Exercise in children and adolescents with diabetes. Pediatric Diabetes 2009: 10 (Suppl. 12): 154-168.

The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.

This material has been developed from sources that we believe are accurate, however, as the field of medicine (in particular as it applies to diabetes) is rapidly evolving, the information should not be relied upon, as it is designed for informational purposes only. It should not be used in place of medical advice, instruction and/or treatment. If you have specific questions, please consult your doctor or appropriate health care professional. 

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