Hypoglycaemia after exercise
As the glycogen stores in the liver are decreased during exercise, there is a greatly increased risk of hypoglycaemia several hours after the exercise. The muscles will have increased insulin sensitivity for at least another 8-10 hours, sometimes up to 24 hours after the exercise is finished. This means that you are likely to be at risk of night time hypoglycaemia after strenuous physical activity. If you find yourself in this situation, you should begin by trying to refill the glycogen stores in your liver and muscles, by eating during and after the exercise. Count on needing an additional 10-15 g (1/3-1/2 ounce) of carbohydrate (15-30 g, 1/2-1 ounce, for an adult) for every 30 minutes of exercise after the initial 30 minutes, or approximately 1 g of glucose/kg body weight per hour. You might find it valuable to experiment with different amounts of carbohydrate during a game of football for example, and when you find a suitable amount, follow this up by eating the same amount of extra carbohydrate every time you play. If you start playing within 1 hour of your injection, the insulin uptake will be increased and you will probably need to increase your carbohydrate intake again or decrease the insulin dose. Remember that it takes more than one meal to refill the glycogen stores in your liver and muscles after heavy physical exertion. This means that even if you have eaten a substantial meal after the game you may become hypoglycaemic later in the day or evening, since the glycogen stores have not had time to be refilled completely.
If you play sport in both the morning and the afternoon, you will be more likely to have problems with hypoglycaemia during the afternoon game for the same reason. Hypoglycaemia can be minimized with appropriate reductions of the premeal doses when using multiple injection therapy with rapid-acting insulin or pumps. What this means, in practice, is that you are likely to need an extra helping at your evening snack if you have been playing sport all afternoon. Your appetite may well remind you of this! However, even though you are eating more, you may still find your need for insulin has gone down, and you may need to decrease the dose at the evening snack by 1-2 units. However, don′t decrease it too much, as the liver needs insulin to refill the glycogen stores. If you have problems with hypoglycaemia in spite of a reduced dose, you need to eat more carbohydrates. More often than not, the increased activity with alcohol can cause particular problems since alcohol blocks the body′s ability to respond to hypoglycaemia. Unconscious hypoglycaemic reactions or hypoglycaemic seizures may result if you forget to decrease your bedtime insulin or to have an extra snack before going to bed.
This content is based on Dr Ragnar Hanas' helpful book, Type 1 Diabetes in children, adolescents and young adults. Click here to order copies of Dr Hanas' book online.
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