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Exercising with Diabetes

We asked FUTURELIFE dietician Bridget Lamont to give us some tips on exercising with diabetes. Here’s what she had to say…


The benefit of regular physical activity is well known to many. It is recommended that adults aim for at least 30 minutes of exercise 5 days a week. Exercise not only has many health benefits and is especially good for people living with Diabetes. Exercising helps to reduce blood sugar levels and also insulin requirements for up to 24 hours. It is however very important to be prepared with the correct snacks before, during and after exercise so that your blood sugars do not drop too low (i.e. hypoglycaemia).

Before you exercise:

If you are going to exercise for only 30 minutes, it is not usually necessary to snack before the time. However if you are planning to exercise for 60-90 minutes, it is a good idea to have a small carbohydrate snack 1 hour before you exercise containing 15g of carbohydrates. For example, this could be a slice of bread, ½ a FUTURELIFE® High Energy Bar, 1 small fruit, 3 provita crakcers or 4 Super C sweets. It is best to check your blood sugar level before you exercise though. If it is more than 10mmol/l, you will not need a snack.

If you are going to exercise for more than 90 minutes, your muscle glycogen stores will get depleted and you therefore need more carbohydrates. Once again it is best to check your blood sugar level before you exercise to see how much carbohydrates you need to take as your pre-training snack 1 hour before exercise. See below for a guideline:


Blood Sugar level Recommended Snack
<  6mmol/l Have 50g Low GI Carbohydrates e.g.

1 Whole wheat sandwich ( with protein) + 1 fruit, OR 1 Cup whole wheat cereal + 250ml fat free milk, OR 50g FutureLife Smart Food + 250ml fat free milk, OR 75g FutureLife Smart Food + water

7-10mmol/l Have 15 – 25g Low GI Carbohydrates e.g.

1 Fruit OR 1 Sandwich (with protein) OR 50g FutureLife Smart Food + water

10-15 mmol/l No snack is needed before exercise
> 15mmol/l DO NOT EXERCISE.

Please note that if you are on rapid acting insulin you do not need to inject insulin for the snack you have before exercise, only for your main meals of the day.

  • During exercise:

When exercising for more than 90 minutes you should aim to have 30-60g of High GI Carbohydrates every hour. This is roughly equal to having 400-800ml of a glucose drink containing 5-10g carbohydrates per 100ml every hour. If you are exercising for less than an hour, rather have water. 30-60 g of High GI Carbohydrate could also include 1 ½ – 2 FUTURELIFE® High energy bars, 8 – 16 wine gums or other small chewy sweets or 1-2 carbohydrate gel (depending on the make of the gel).

  • After exercise:

After endurance exercise of more than 90 minutes you should have a recovery drink or meal within 30-60 minutes after exercise. Aim to have 1g of High GI carbohydrates per kg of body weight to restore muscle and liver glycogen stores. This is only necessary if you are exercising again the next day or if your blood sugar levels are low or dropping rapidly after the event. You can aim to have around 600-1000ml of a glucose drink within 30-60 minutes and then have your next healthy low GI meal within 2 hours after exercise. Great post exercise snacks include flavoured milk, FUTURELIFE® High Protein Lite bar or a Low GI sandwich with some form of protein (e.g. chicken).

It might also be necessary to alter your Insulin requirements on the day of the endurance event lasting more than 90 minutes. It is best to inject your insulin into the non-exercising muscles. For instance, if you are running or cycling, rather inject into your abdomen than your legs or arms. You can decrease your rapid acting insulin with your meal before the event by 30-50%. Try to have this meal 2-3hrs before the event.  If you take your insulin too close to the time you start exercising, it might peak while you are exercising, resulting in a low. You can also reduce your rapid acting insulin with your meal after the event by 30% to prevent low blood sugar which can still occur up to 4 hours after exercise. If you will be exercising for more than 5 hours you can also reduce your long acting insulin the night before the event with 30-40%.

Please note that this information is only a guideline, it is still best to consult your Doctor, Diabetes Educator or Dietitian to calculate your individual requirements.

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  1. Steff Steff

    This is a great article. I didn’t know that I should be checking my sugar levels before exercising. That table showing the different levels and then what to eat is brilliant. I’m going to print it out and put it up on my fridge.

  2. Keni B Rossy Keni B Rossy

    Hi there

    Please forgive me if this is a silly question… But why should I not exercise if my blood sugar is more than 15?


  3. Briget Briget

    Hi Kendall

    Thank you for your question and it is definitely NOT a stupid one.

    I should probably have been more specific with regards to the TYPE of exercise as this can have different effects on your blood glucose levels.

    Anaerobic exercise (e.g. short duration, but high intensity such as sprinting, weight lifting and skipping etc.) can cause the release of glycogen and adrenaline, which can cause an increase in the blood glucose levels. On the other hand, aerobic exercise (such as cycling, walking, swimming or long distance running) lasting for longer periods of time at lower intensities will lower your blood glucose levels.

    So if you are going to do anaerobic exercise and your blood glucose readings are as high has 15mmol/L, this could push it up even further to dangerous limits. If you are planning on doing low intensity exercise for longer period of time, it might bring your blood sugar down. But please consult your medical doctor before attempting any form of exercise. The above article is purely a guideline.

    Thanks again for your question.

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Sweet Life is a registered NPO/PBO (220-984) with a single goal: to improve diabetes in South Africa. We are funded by sponsorships and donations from aligned companies and organisations who believe in our work. We only share information that we believe benefits our community. While some of this information is linked to specific brands, it is not an official endorsement of that brand. We believe in empowering people with diabetes to make the best decisions they can, to live a healthy, happy life with diabetes.