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From Merrill, Wisconsin, USA:

I recently attended an intensive wrestling camp to prepare for the national Greco/freestyle competition in Fargo, North Dakota. Workouts consisted of a hard run in the morning and two intense workouts later in the day. Throughout the camp, I would experience extreme lows, 38 mg/dl [2.1 mmol/L] to 45 mg/dl [2.5 mmol/L], but they would usually be at night. I had lowered the amount of my usual insulin dosage, but I continued to have lows. At the last practice that I attended, I was unable to raise my blood sugar above 40 mg/dl [2.2 mmol/L]. As a result, I had to leave practice. Usually, during practice,I would have a Gatorade on mat side to raise my blood sugar. I drank three Gatorades within 45 minutes and my blood sugar would not go above 40 mg/dl [2.2 mmol/L]. After an hour of lying in bed at home, my blood sugar finally went up to 140 mg/dl [7.8 mmol/L]. I was not cutting weight at this camp and I ate a diet that consisted of more complex carbohydrates than I would normally consume. Do you have any tips on how to keep my blood sugar in a good range for athletics?


Hypoglycemia during exercise usually means there is too much insulin on board. There are several things to do that can decrease the chance of having low blood sugars during exercise. One, is too eat extra food (i.e., carbohydrates) to increase blood sugar prior to exercise. Two, is to decrease insulin a couple of hours prior to exercise. This can be done through basal insulin (i.e., temporary basal on an insulin pump) or decreasing the bolus (shot or with an insulin pump) when eating food prior to exercise. Third, is to check your blood glucose twice prior to exercise (at one hour and one-half hour) to see which direction your blood glucose is going so you can react accordingly. There are also 30 minutes to deal with a low or high blood sugar that probably will not disrupt the start of exercise.

Hypoglycemia after exercise can be a very frustrating experience. For individuals who use insulin and are active, the likelihood of a low blood sugar is high if preventive measures are not taken. The problem is not so much that it can occur but it is so unpredictable. It is common to have low blood sugars after exercise. In fact, there is a high occurrence for people four to six hours after exercise but some experience it up to 24 hours later.

Once the body burns the food eaten prior to exercise it uses a stored form of glucose (called glycogen) in the liver and muscles. After that, it is depleted and if food is not eaten, the body will get glucose from the blood, which causes us to go low. This does not happen quickly but over a number of hours. There is a twofold reason for eating carbohydrates after exercise. One is to help prevent a low, but probably just as important is to restore the glycogen lost during exercise. This will not only help with decreasing the chance of a low blood sugar but will help with performance for the next exercise bout.

Now that you know why it happens, the question becomes, what can be done to prevent this? There is no easy answer, but if you follow a few guidelines the risk of hypoglycemia will decrease. Some tips to follow for individuals who experience low blood sugars after exercise are:

Aerobic exercise, such as running, cycling, etc., will usually decrease blood sugars, so providing a buffer with a starting blood sugar higher than normal is recommended. Many athletes shoot for a starting blood sugar of approximately 150 mg/dl [8.3 mmol/L] prior to exercise, but it may be lower or higher depending on the individual and intensity of exercise. When insulin is involved, the guidelines are to have blood sugars above 100 mg/dl [5.6 mmol/L], but not higher than 240 mg/dl [13.3 mmol/L] to 300 mg/dl [16.7 mmol/L] with ketones or 300 mg/dl [16.7 mmol/L] whether there are ketones or not.

Anaerobic exercise, such as weightlifting, sprinting, or wrestling, can cause blood sugars to go up during or immediately after the exercise due to the increased activity of hormones such as adrenaline. Even though there may be an increase, there is a likelihood blood sugars will go low hours after the activity. Once blood sugars are near normal, it is important to eat to replace glycogen stores. You should be drinking a lot of water and discuss with your healthcare team using insulin to bring down high blood sugars immediately after exercise (i.e., over 300 mg/dl [over 16.7 mmol/l].

Decreasing the long acting insulin when there is a planned exercise event is one way to prevent low blood sugars. Increasing carbohydrates prior to the activity and afterwards is another way. Finally, a combination of decreasing insulin and increasing carbohydrates can work, too. This is advantageous because it is important to eat carbohydrates to help fuel the body for the activity, but decreasing insulin along with it may help for individuals who do not want to eat too much food (i.e., carbohydrates) prior to exercise if weight loss is a goal.

Decreasing the basal rate for pump users after exercise - a 50% reduction rate is a good starting point over four to six hours, but check frequently to see if more or less is needed and whether to decrease/increase the time of the decreased basal rate. Since most low blood sugars occur in individuals in the middle of the night, often between 1 and 3 a.m., having a reduced rate overnight may help as well.

A good rule is to eat 15 grams of carbohydrates for every 30 to 60 minutes of exercise -- this is individualized so checking blood sugars during exercise will help determine how many carbohydrates are needed.

Eat carbohydrates with some protein or a good source of fat, such as peanut butter, within 20 to 30 minutes after exercise to restore glycogen stores. How much depends on blood sugars and intensity of exercise.

These are guidelines to follow, but are not absolute. If a pattern develops, look to make changes up or down depending on blood sugars and make sure to keep your healthcare team in the loop with any changes made.


Original posting 25 Jul 2007
Posted to Exercise and Sports and Hypoglycemia


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Last Updated: Tuesday April 06, 2010 15:10:12
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