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Advice for people with diabetes and their families

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Exercise and blood sugar levels

Although exercise can lower blood glucose (sugar) levels, being physically active can affect your blood sugars 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

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 exercise. You may find them useful to refer to when you are preparing to get active.  

Starting blood sugar levels Recommendations
Less than 5mmol/l Eat or drink 10-20g of carbohydrate before you start getting active, and wait until your blood sugar levels are above 5mmol/l.
Between 5 - 8mmol/l Eat or drink 10g of carbohydrate before you begin your physical activity. You can then start moving. 
Between 8 - 15mmol/l You can begin your activity.
Greater than 15mmol/l

Check your blood ketone level. If no ketones are present, you can start your activity. You may also need to take a small correction dose of insulin. 

If your ketone level is less than 1mmol/l, you may need to take a small correction dose of insulin before exercising. You should then continue to check your blood sugar level. 

If your ketone level is between 1-1.4mmol/l, take a correction dose of insulin and wait 1 hour before you begin your activity. You will need to continue to check your blood sugar level. 

If your ketone level is above 1.5mmol/l, make sure to follow our advice about what to do if your ketone levels are high

These recommendations are only guidance, and your individual experience when exercising may differ.

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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