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Blood sugar levels and exercise

Although exercise can lower blood glucose (sugar) levels, being physically active can affect your blood sugar levels in different ways. Depending on the type of activity you’re doing, you might experience your blood sugar level going up or down. 

We know this may leave you feeling worried about starting something new, especially if you treat your diabetes with medication that puts you at risk of hypos, such as insulin or sulphonylureas. Our information about hypo-anxiety will help you understand and manage these feelings, so you can begin to feel more confident about starting to get active

Learning more about what happens before, during and after you get active can also help to ease some of this worry. To support you with this, we've put together information about the steps you can take to try and manage the effects of exercise on your blood sugar level

Two ladies with diabetes walking together and enjoying exercising

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Blood sugar levels before exercise 

If you check your blood sugars yourself, whether that’s using diabetes technology or test strips, try doing this more often around the time you’re starting to exercise.

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.  

To help you get started, 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.  

Starting blood sugar levelsRecommendations
Less than 4mmol/lYour 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. 
4 - 7mmol/l

This is usually the healthy target range you should aim for.

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/lYou 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 – e.g. 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 also need to continue to check them for up to 24 hours after this. 

Exercise and insulin   

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.  

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. 

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