Key Takeaways
- Regular physical activity improves insulin sensitivity and supports long-term blood glucose management
- Aerobic exercise generally lowers blood glucose; intense or resistance exercise can temporarily raise it
- People on insulin need to plan carefully around exercise to reduce hypoglycaemia risk
- Post-meal walks — even 10 minutes — can help moderate post-meal glucose rises
- An exercise physiologist can design a safe, personalised programme — often accessible via a GP Management Plan
Physical activity is one of the most well-established tools for managing blood glucose in both type 1 and type 2 diabetes. It improves how efficiently the body uses insulin, supports healthy weight management, reduces cardiovascular risk, and has significant benefits for mental wellbeing.
However, exercise affects blood glucose in complex and sometimes counterintuitive ways — and for people using insulin, understanding those effects is particularly important for staying safe. This guide explains what happens to blood sugar during different types of exercise, how to manage glucose around physical activity, and practical approaches for getting started.
Why Exercise Affects Blood Glucose
During physical activity, working muscles need energy. They can draw glucose directly from the bloodstream and from stores of glycogen (a form of glucose stored in muscle and liver tissue). This glucose uptake during exercise happens partly without requiring insulin — meaning muscle contractions themselves trigger glucose transport into cells through a separate mechanism. This is one reason why exercise can lower blood glucose even in people with significant insulin resistance.
After exercise, muscles also replenish their glycogen stores by drawing glucose from the blood, which is why blood glucose can continue to fall for several hours after a workout ends. For people on insulin, this delayed effect is an important consideration in managing post-exercise hypoglycaemia risk.
Aerobic vs Resistance Exercise: Different Effects
The type of exercise matters, because aerobic (cardio) and resistance (strength) training have meaningfully different effects on blood glucose.
🏃 Aerobic Exercise
- Brisk walking, jogging, cycling, swimming, dancing
- Generally lowers blood glucose during and after activity
- Effect depends on intensity — moderate intensity lowers glucose most consistently
- Very high intensity (sprinting) can temporarily raise glucose due to adrenaline release
- Hypoglycaemia risk is highest during and for several hours after moderate-intensity aerobic exercise in insulin users
🏋️ Resistance Exercise
- Weights, resistance bands, bodyweight exercises
- Can cause a temporary rise in blood glucose during the session due to stress hormone release
- Followed by improved insulin sensitivity and lower glucose in subsequent hours
- Lower risk of immediate hypoglycaemia than aerobic exercise
- Builds muscle mass, which improves long-term glucose metabolism
Combining both types is most beneficial
Research suggests that combining aerobic and resistance exercise in the same session — doing resistance exercise before cardio, or mixing short bouts of both — may help moderate the glucose-lowering effect of exercise and reduce hypoglycaemia risk for insulin users, compared to aerobic exercise alone. This approach is worth discussing with your exercise physiologist or diabetes care team.
Exercise Recommendations for People with Diabetes
Diabetes Australia and the RACGP broadly align with Physical Activity Australia guidelines in recommending that adults with diabetes aim for:
- 150–300 minutes of moderate-intensity aerobic activity per week (e.g. 30 minutes most days), or 75–150 minutes of vigorous-intensity activity
- Two or more sessions of resistance training per week, targeting major muscle groups
- Minimise prolonged sitting — breaking up sedentary time every 30 minutes with light movement has measurable benefits for blood glucose
These are general targets. If you are new to exercise, starting with even 10–15 minutes of gentle walking per day and gradually building up is a clinically sound approach. Any increase in activity is beneficial — do not let the "ideal" target discourage you from starting somewhere manageable.
Post-Meal Walking and Blood Glucose
Research has shown that short walks taken after meals can help moderate the rise in blood glucose that follows eating. This occurs because muscle contractions during walking promote glucose uptake independent of insulin — a particularly useful mechanism for people with insulin resistance.
Several studies have found that walking for 10–15 minutes after a meal is associated with lower post-meal glucose levels compared to remaining sedentary after eating. While the effect is meaningful, it is one tool among many — and individual responses to post-meal walking vary. If you use a CGM, it can be informative to observe your own post-meal glucose pattern with and without a short walk.
Managing Blood Glucose Around Exercise: Type 1 Diabetes
For people with type 1 diabetes using insulin, exercise requires careful planning to manage hypoglycaemia risk. There is no single correct approach — strategies are highly individual and should be developed with your endocrinologist or diabetes educator. Common considerations include:
Before exercise
- Check blood glucose before starting — if below 5.0 mmol/L, consume 15–30g of fast-acting carbohydrate before beginning
- If using a CGM, check the trend arrow — a falling glucose is a warning sign even if the current level appears acceptable
- Consider reducing your pre-exercise bolus insulin if eating within a couple of hours before activity
- Avoid injecting insulin into muscles that will be heavily used during exercise, as absorption may be faster
During exercise
- Keep fast-acting carbohydrate (glucose tablets, sports drink, jelly beans) accessible at all times
- For extended sessions (over 60 minutes), you may need to consume carbohydrate during activity — approximately 30–60g per hour of moderate exercise, depending on individual response
- If using an insulin pump, discuss a temporary basal rate reduction with your healthcare team
After exercise
- Blood glucose can continue to drop for up to 12 hours after exercise — particularly after afternoon or evening activity
- Consider a small carbohydrate snack after exercise if glucose is below 7.0 mmol/L
- Set CGM alerts to a slightly higher threshold overnight after significant daytime exercise
- Monitor more frequently than usual in the hours following exercise
| Blood glucose before exercise | Recommended action (type 1, on insulin) |
|---|---|
| Below 5.0 mmol/L | Consume 15–30g fast-acting carbohydrate; recheck before starting |
| 5.0–7.0 mmol/L | Consider a small carbohydrate snack; monitor closely during exercise |
| 7.0–14.0 mmol/L | Generally safe to exercise; monitor during and after |
| Above 14.0 mmol/L | Check for ketones; if elevated, postpone exercise and seek medical advice |
These are general guidelines only
Individual glucose responses to exercise vary enormously. The thresholds above are starting points — your personal targets and strategies should be set in consultation with your endocrinologist or credentialled diabetes educator, who can tailor advice to your specific insulin regimen, fitness level and glucose patterns.
Exercise and Type 2 Diabetes
For people with type 2 diabetes who are not using insulin or sulphonylureas (a class of medication that can cause hypoglycaemia), the risk of exercise-induced hypoglycaemia is much lower. Exercise can generally be started and progressed with fewer blood glucose precautions, though checking blood glucose before and after unfamiliar or intense new activities is prudent.
For those on sulphonylureas (such as gliclazide), hypoglycaemia during exercise is possible. Speak with your GP about whether your dose or timing may need adjustment to accommodate a regular exercise routine.
Getting Started Safely
If you have not been exercising regularly, or if you have other health complications from diabetes (such as neuropathy, retinopathy or cardiovascular disease), it is important to speak with your GP before starting a new exercise programme. Your GP can assess whether any precautions or investigations are needed before you begin.
An Accredited Exercise Physiologist (AEP) can design a programme tailored to your health status, fitness level, and diabetes management goals. Exercise physiologists are allied health professionals with specialist training in exercise for chronic conditions, and consultations are often partially covered by Medicare through a GP Management Plan.