The factors that someone with type 1 diabetes needs to consider are:
1. Hypoglycaemia (low blood glucose) is more likely to occur with exercise because:
- The blood stream, liver and muscles ‘burn up’ glucose to release energy
- The cells of the muscles become more sensitive to insulin for up to 12-16 hours after exercise, particularly after very intense/prolonged exercise
- Some people may hypo during or immediately after exercise, others hypo many hours later, overnight or the next morning
- Muscles that are exercised can continue to take up glucose without insulin
- Extra glucose is moved from the bloodstream to replace liver and muscle stores
2. Hyperglycaemia (high blood glucose) can occur:
- Following brief/intense exercise such as competitive sports, the body produces an increased amount of the hormone adrenaline
- Adrenaline stimulates the release of glucose from the liver - blood glucose may later fall.
- When blood glucose levels are high (15mmol/L) the body may start producing ketones, indicating that there is not enough insulin in the body
- In this situation, exercise will not help to reduce glucose levels, in fact it may cause them to increase further
- Usually, extra insulin is needed
How to avoid hypoglycaemia
Understanding how your body responds to exercise is important and monitoring your blood glucose before, during and after exercise can give you that information. Factors such as the duration and intensity of your exercise and your current blood glucose level can help you work out how much extra carbohydrate to eat and if you need to reduce your insulin dose.
- You may need to reduce your insulin dose before/after exercise or at bedtime. Speak to your doctor or diabetes educator about how to do this safely
- Check your blood glucose before, during and after exercise
- Carry glucose such as jelly beans or Lucozade or sports drink to treat a hypo
- Make sure your BGL is above 6mmol/L before starting exercise
- Avoid injecting into the arms or legs as your insulin may work more quickly and increase the risk of a hypo - the rate of absorption is more consistent when injecting into the abdomen or buttocks
- Replenish your liver glucose stores by eating extra carbohydrates after exercising
- Prevent delayed hypoglycaemia overnight or on waking by having a carbohydrate snack before bed
Tips on how to avoid hypoglycaemia during exercise
Dos and don’ts of exercise
- Never completely omit insulin or hyperglycaemia and ketones could develop
- If your blood glucose is high (over 15 mmol/L) and ketones are present or blood glucose is over 20 mmol/L do not exercise. Take extra insulin and delay exercise (refer to sick day action plan)
- If you have diabetes complications you need to take some precautions as your ability to tolerate exercise may be reduced
- Certain diabetes related complications can be worsened by some types of exercise
- Speak to your doctor about your exercise program as they can help identify exercises to be avoided/modifyed e.g. straining and jarring exercises should be avoided if you have retinopathy.
- If you have had type 1 diabetes for 15+ years, are aged over 35, have risk factors for heart disease, or have diabetes complications, schedule a check up with your doctor before starting any new exercise
- Check ups should include ECG, blood pressure, feet, kidney, eye checks, autonomic nerve function (these checks should also be part of your annual diabetes check)
- Warm up and cool down
- Wear well fitting sports shoes, that have adequate shock absorption
- Drink plenty of fluid to keep hydrated
Further information and resources
- Sign up to the Hypoactive team - a community network focused on supporting people living with type 1 to get active and healthy.
