Windfal - Tricky Situations - Exercise - Introduction
Objective: To develop skills to cope with the effect of exercise on blood glucose

Exercise can improve your health. It can:
  • Protect against heart disease
  • Help control weight
  • Be enjoyable!
For people on insulin, exercise can be tricky because of effects on your blood glucose.

First two general points:
  • Different types of exercise in different people can cause different effects on their blood glucose. So you may need to experiment a little to find out what suits you.
  • Remember exercise is not just sport - it can be any activity such as gardening, house cleaning or shopping.
What happens to your blood glucose during exercise? It can go up or down.

Low blood glucose (Hypoglycaemia): Exercise increases the speed that your body uses glucose because it is an energy source for muscles. Also, if you inject insulin into your leg or arm and then exercise using that limb, this can increase the blood flow and so the insulin may be absorbed more rapidly.

High blood glucose (Hyperglycaemia): If there is a shortage of insulin when you exercise, glucose cannot enter the muscle cells and the blood glucose level increases. Various stress hormones are also released during exercise and these can cause a release of glucose from stores in the body.

So what should you do?


1. Plan ahead:
  • If you can plan your exercise, this means you can choose whether to reduce your insulin or eat more carbohydrate. If you are exercising to lose weight, it would be best to reduce your insulin dose (rather than eating more calories).
  • If you do unplanned exercise, you may need to have extra carbohydrate.
2. Check your blood glucose before you exercise:
  • This will help you to make any necessary adjustments.
3. If your blood glucose is high (over 13 mmol/l): 
  • Remember that exercise can increase your blood glucose, particularly if your diabetes is generally poorly controlled.
  • Check for ketones and if these are present, postpone the exercise until the blood glucose is below 13 mmol/l.
  • Consider injecting an extra dose of fast acting insulin.
4. Remember that hypos can be more difficult to detect during exercise:
  • Many people have symptoms of a rapid heart rate or feeling hot and sweaty when hypo. You may also feel these during normal exercise, so the situation can be unclear.
5. Always carry rapidly absorbed glucose with you when exercising:
  • For example, this could be dextrose tablets, a glucose drink or jelly babies.
6. Make sure someone with you knows what to do if you have a hypo:
  • This could be a friend or the person leading the exercise class.
7. Aways carry something that identifies you as having diabetes.

8. Keep well hydrated:
  • This is important for anyone doing high intensity exercise, to replace lost fluid. You could also choose a fluid that provides some carbohydrate, such as diluted glucose drinks or squash.
 9. Remember that if your blood glucose is steady, this gives the best performance:
  • If you can avoid large swings in your blood glucose during exercise, both very high and very low levels, this will improve your physical performance.
  • So for example, try to avoid having a large glucose drink immediately before exercise. Instead, take small sips regularly throughout the exercise. Or take regular jelly babies - they work just as well!

Ultimately you will need to experiment a little. Just remember these general rules and see what works for you.

For advice on adjusting your insulin during exercise, go to:

'Tricky-situations - Exercise: Adjusting your insulin'

Click here to go back to 'Tricky situations'.

But remember there is more information in the 'Quiz'. Come on, you know you want to try it!

Last updated06 Jun 2022
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