Understanding how exercise affects your blood glucose levels helps you stay active safely and confidently.
Here's what many people don't realise: different types of exercise affect your blood glucose differently. With the right preparation and adjustments to insulin and carbohydrates, you can enjoy all forms of physical activity while keeping your blood glucose in target range.
What you will learn in this fact sheet
This fact sheet provides practical guidance to help you exercise safely with type 1 diabetes.
- Key safety considerations before, during and after exercise.
- How to adjust your insulin for different types of activity.
- Carbohydrate requirements for various exercise intensities.
- Managing hyperglycaemia and ketones before exercise.
Before exercise
Hypoglycaemia considerations
- Avoid exercise if you've had a severe hypo in the past 24 hours (when you needed assistance from someone).
- If your glucose level is less than 5mmol/L, consume 10–20 grams of carbohydrate before starting.
- After a recent mild hypo, be cautious with monitoring and avoid high-risk activities like swimming alone, rock climbing or alpine skiing.
Hyperglycaemia management
If your glucose level is more than 15mmol/L before exercise, check blood ketones and follow these guidelines:
- No ketones or less than 0.6mmol/L: Take 30% of your usual correction dose and proceed with low- to moderate-intensity exercise.
- Ketones 0.6–1.4mmol/L: Take 30% of your usual correction dose and limit to low-intensity exercise for less than 30 minutes.
- Ketones 1.5mmol/L or greater: Take your normal correction dose and do not exercise.
Ketones greater than 3mmol/L: Seek urgent medical attention immediately.
Insulin adjustments
Multiple daily injections
Plan exercise at least 1–2 hours after rapid-acting insulin injections when possible.
If exercising within 1.5 hours of your meal bolus, reduce your insulin using this guide:
30-minute exercise:
- Low intensity (walking): Reduce by 25%.
- Moderate intensity (swimming, brisk walking): Reduce by 50%.
- High intensity (running): Reduce by 75%.
- Very high/anaerobic (uphill cycling, weights): No adjustment needed.
60-minute exercise:
- Low intensity: Reduce by 50%.
- Moderate intensity: Reduce by 75%.
- High/very high/anaerobic: No adjustment needed.
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Carbohydrate intake
Before exercise
Your carbohydrate needs depend on your glucose level, insulin on board, and exercise intensity.
If glucose is less than 5mmol/L:
- Low intensity: 10–20g without active insulin, or 15–30g with active insulin.
- Moderate intensity: 10g (aerobic exercise only).
- High intensity: Delay exercise until glucose is above 5mmol/L.
If glucose is 5–15mmol/L:
- Generally no additional carbohydrates needed, though anaerobic and high intensity exercise may cause glucose to rise.
During exercise
Monitor glucose every 30 minutes during activity. Carbohydrate requirements increase with duration:
Low intensity (walking, housework):
- 60+ minutes: 15–30g per hour.
Moderate intensity (jogging, cycling, tennis):
- 0–30 minutes: 15g.
- 30–60 minutes: 15–30g.
- 60+ minutes: 30–45g per hour.
High intensity (running, football):
- 0–30 minutes: 15–30g.
- 30–60 minutes: 30–45g.
- 60+ minutes: 45–60g per hour.
Always carry rapid-absorbing carbohydrates like jelly beans, glucose gels or sports drinks during activity.
After exercise
Hypoglycaemia risk continues for at least 12 hours after exercise due to increased insulin sensitivity.
Key recommendations:
- Check glucose levels regularly for up to 8 hours after exercise.
- Monitor overnight after new, prolonged or high-intensity exercise.
- Reduce rapid-acting insulin for your next meal by 20–75%.
- Consider reducing evening long-acting insulin by approximately 20%.
- Consume 20–30 grams of protein with carbohydrate within 2 hours of exercise (e.g. milk-based smoothie) to prevent hypoglycaemia and support muscle recovery.
Understanding exercise types
Different exercise types affect your glucose differently:
- Flexibility/stretching
Minimal immediate glucose change. - Aerobic (running, cycling)
Typically lowers glucose levels. - Anaerobic (weight training, sprints)
May raise glucose levels initially due to stress hormones. - Mixed exercise
Can cause variable glucose changes.
Monitor your patterns to understand your individual responses.
Download the fact sheet
Need personalised advice?
Consult an Accredited Practising Dietitian or your diabetes care team.