Although exercise can lower blood glucose (sugar) levels, different types of physical activity can affect your blood sugar levels in different ways.
You might find your blood sugar levels going up or down — and at different rates — depending on the type of physical activity you’re doing, how much effort you’re putting into it, how fit you are and if your heart rate is increasing.
Anything you do at a comfortable pace, such as walking, jogging, yoga, cycling or swimming, tend to make your blood sugar levels lower. And physical activity where you’re doing lots of bursts of short, sharp movement, such as sprinting, squash or HIIT workouts (high intensity interval training), would tend to make your blood sugar levels higher. And if you’re doing something like stretching, your blood sugar levels may stay the same.
But it can depend on the circumstances. Stress can also make your blood sugar levels go higher. For example, this could happen when you’re playing in a tournament.
We know if you use insulin or other medication that lowers your blood sugar levels that you can worry about hypos. So to give you the confidence to try new activities or increase activity levels, we’ve set out guidelines on blood sugar levels when exercising. And explain what happens to your blood sugar levels before, during and after activity.
To help you get started, below we’ve put together a set of general guidelines around blood sugar levels and moving more for people who test their blood sugars. You may find them useful to refer to when you are preparing to get active.
Blood sugar levels before exercise
If you check your blood sugars yourself, whether that’s using a continuous glucose monitor or test strips, try doing this more often around the time you’re starting to exercise. See our guidelines below.
Trial and error can help you to spot patterns but remember to stay safe. If you begin exercising when your blood sugar levels are high, you may experience dehydration and tiredness. This can make it harder for you to do your activity, so it’s important to drink more and keep hydrated.
Guidelines on blood sugar levels when exercising
These recommendations are only guidance, and your individual experience when exercising may differ. If you are using an insulin pump the guidance will be different. You should speak to your healthcare team about what's best for you.
What should blood sugar levels be before exercising?
Before starting exercise your blood sugars should ideally be between around 5.6 -12mmol/l. But this is a guide and may vary for you individually depending on the type of medication you take and the type of exercise you are doing. If you are taking up a new activity it is useful to talk to your healthcare team and agree a plan for managing your blood sugars during exercise.
Do not exercise if your blood sugar levels are 4mmol/L or lower – or if you use any kind of insulin pump 3.5mmol/L or lower. Your healthcare team should provide you with an individual plan for treating hypos and let you know how many additional carbs you may need during exercise, depending on levels.
If you have a hybrid closed loop insulin pump, consider using the activity or temporary target setting for around 90 minutes before and during your exercise.
| Starting blood sugar levels | Am I ready to start exercising? Check our recommendations below |
|---|---|
| Less than 4mmol/l | Your blood sugar levels are too low and you need to have your usual hypo treatment, such as glucose tablets or sugary drinks, followed by some starchy carbs, such as a banana or a cereal bar, to stop your levels going low again. Wait 15 minutes and check your blood sugar levels. |
| 4 - 7mmol/l | This is usually the healthy target range you should aim for throughout the day. If you are going to start moving, you may need to have a snack with starchy carbs beforehand to make sure your blood sugar levels don’t go too low. If you aren’t having a snack, try to check your blood sugars regularly during your activity. |
| 7 - 13mmol/l | You can begin your activity. As different types of movements can cause your blood sugars to go higher or lower, try to check them regularly during your activity. |
| Above 13mmol/l | Your blood sugar levels are above target levels and getting active could cause them to rise even higher. It’s important to speak to your healthcare team as you may need to think more about the type of activity you are planning to do and possible changes to your treatment. If you’re not sure why your blood sugar levels are high and you’ve been taught how to test for ketones, you should test your urine or blood for ketones and follow the advice from your healthcare team about how to avoid becoming unwell. |
These recommendations are only guidance, and your individual experience when exercising may differ. You should speak to your healthcare team about what's best for you.
Exercising if you’ve had a hypo or severe hypo in the last 24 hours
If you’ve had a severe hypo in the last 24 hours, do not do any physical activity.
If you’ve had a hypo in the last 24 hours, your risk of having a hypo will be higher so it’s important to be careful when exercising. Try not to do any activity on your own, and make sure you follow our tips below.
Managing your blood sugar levels when exercising
Some days you might do exactly the same type of activity and eat the same foods, but your blood sugar levels may be completely different to what you’d expect. This is completely normal, but we know it can be really frustrating.
Although everyone manages their diabetes differently, these tips can be a useful starting point to build your confidence and get you moving:
- if you normally check blood sugars, keep a record of what happens when you’re being active and show this to your diabetes nurse or doctor
- if you’re at risk of hypos, keep hypo treatments handy, as well as a snack with some carbs in – eg a sandwich, a piece of fruit or a cereal bar
- wear your diabetes ID so people around you can help if they need to
- if you use insulin to treat your diabetes, you might need to make changes to your dose when exercising.
You may also want to speak to your healthcare team for more advice.
"I always test my blood sugar before I go for a walk and always take plenty of hypo treatments with me."
- in his story, David shares his tips about managing his diabetes when walking.
Blood sugar levels after exercise
Some people may find that their blood sugar levels go up after exercise, while others may find that moving more lowers their levels. Because different types of activities can affect your blood sugar levels in different ways, it’s important to check your blood sugars after you finish exercising. You may need to continue to check them for up to 24 hours after this.
How long does blood sugar stay elevated after exercise?
Exercise can improve how well your body responds to insulin for up to 24 hours, so some people may find their blood sugar levels can be higher for a day or so afterwards. If that’s the case for you, continue checking your blood sugar levels more regularly for the next 24 hours.
Exercise and insulin
It’s important to check your blood sugar levels before and after physical activity.
One of the benefits of being more active is that it can increase how well your body uses insulin to bring your blood sugar levels down. This may mean you need to adjust your dose before, during or after you exercise, depending on how long you’re moving for and the type of activity you’re doing.
And it’s important to check your blood sugar levels after you finish exercising. You may also need to continue to check them for up to 24 hours afterwards – as your body can respond better to insulin after activity for that long.
It’s best to speak to your healthcare team for more information, as they’ll be able to look at your activity levels and help you make the right changes to your dose. If you use a Continuous Glucose Monitor, you will be able to see the effect of any activity you do on your blood sugar levels.
