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From Michigan, USA:

My 17 year old son, who is 5 feet, 9 inches and weighs 125 pounds, was diagnosed with type 1 diabetes three weeks ago. He presented with blurry vision, a blood sugar of 645 mg/dl [35.8 mmol/L] and an A1c of 9.1. He was started on NovoLog 70/30 twice a day, 10 units with breakfast and 12 units with dinner. His sugars have been between 60 and 120 mg/dl [3.3 and 6.7 mmol/L] pre-meals and 60 to 100 mg/dl [3.3 to 5.6 mmol/L] before bed. He is a cross country runner. He was running about 5 to 7 miles per day before being diagnosed with diabetes. His vision is now normal he wants to start running again. Do you have any suggestions about what his blood sugars should be before he runs? His endocrinologist thinks 150 mg/dl [8.3 mmol/L]. I'm concerned because his blood sugar is never over 120 mg/dl [6.7 mmol/L] now that he is on insulin.

Also, he still feels "shaky" with his blood sugar levels 60 to 120 mg/dl [3.3 to 6.7 mmol/L]. Our endocrinologist said this will get better as his body adjusts to the sugar levels. Do you have any suggestions?


Typically, aerobic exercise will cause the blood sugar to drop, although, it can increase if not enough insulin is on board. It is not usual for blood sugars to drop 50 mg/dl or more during 30 to 45 minutes of cross country training. The American Diabetes Association recommends a delay in exercise for individuals with type 1 diabetes if their blood sugar is less than 100 mg/dl [5.6 mmol/L]. It is not wise to start a training run or competition with a blood sugar of 100 mg/dl [5.6 mmol/L] if a typical response to this type of exercise is a drop in blood sugar of at least 50 mg/dl. Starting a run at 150 mg/dl [8.3 mmol/L] is a better number because it creates a buffer for the anticipated drop. It is important to check blood sugars often to see how certain activity can effect blood sugars. Once you get an idea of the duration/intensity and how it changes blood sugar, a pre-exercise number can be given as a goal. While 150 mg/dl [8.3 mmol/L] is good number to shoot for, maybe 130 mg/dl [7.2 mmol/L] or 170 mg/dl [9.4 mmol/L] is better after checking around the activity. Make changes based on trends, not one or two episodes.

Most athletes struggle more with low blood sugars after exercise rather than during. There is what is known as a "lag effect" which happens hours after exercise. Sometimes this can be up to 24 to 36 hours. It is very important to snack after exercise to help reduce the risk of hypoglycemia and to replace glycogen stores lost during the activity.


[Editor's comment: Be sure to read our Top 10 Exercise Traps and Tips to Avoid Them as well as previous questions on Exercise and Sports. Please consult with your endocrinologist about what foods/drinks to use to ensure your son's blood sugar level is high enough before beginning to exercise. BH]

Original posting 22 Nov 2005
Posted to Exercise and Sports


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Last Updated: Tuesday April 06, 2010 15:10:04
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