Diabetes Type 1 and Physical Activity

What is diabetes type 1?

Type 1 diabetes is a serious condition that causes blood sugar to rise because the body is unable to produce enough insulin - a hormone that helps blood sugar be stored and used for energy. Without insulin, sugar builds up within the bloodstream until levels become so high that serious complications can occur.1

Diabetes can be a debilitating disease and cause stress surrounding how to regulate blood sugar during physical activity. Physical activity is vital for good diabetes management: it improves blood sugar control and increases insulin sensitivity while benefiting both physical and mental health.

Diabetes is a lifelong condition that can cause life-changing complications. However, by following a healthy diet and lifestyle that includes physical activity, you can make sure those complications become far less likely.

What happens to blood glucose when you exercise?

It is likely your blood sugar level will fluctuate whilst exercising. This is perfectly normal, but diabetes requires attention to make sure blood glucose stays in a range that keeps your physical performance remaining optimal too.

Although exercise is important to get the very best control over diabetes, a few extra steps should be taken to make sure your blood sugar remains stable throughout. Remember, the term ‘exercise’ does not specifically mean participation in sport or the requirement of a gym membership, but is anything that causes ‘bodily movement produced by skeletal muscles that requires energy expenditure’.

When performing a high-energy exercise such as weight-training or sprinting, the demands placed on the body require a quick fix of energy, which has been shown to elevate blood sugar.2 On the other hand, steady cardiovascular exercise is more likely to cause a slow drop in your blood glucose.3

Staying safe when exercising with type 1 diabetes

With this possibility of your blood sugar levels changing as you exercise, it’s important to start off knowing exactly where you are. Here is a quick checklist of things to do before you begin.4

  • Test blood sugar before, during, and after exercise, especially when starting out. Bear in mind that exercise can potentially affect blood sugar for 24-36 hours after
  • It is especially important to test blood sugar pre-exercise, as hypoglycaemia (low blood sugar) before exercise increases the likelihood of blood sugar dropping both during and after exercise.5 If you find your blood glucose is too low before exercise, be sure to correct and re-test before beginning
  • Have snacks to hand to quickly lift blood sugar
  • Make sure not to inject insulin into a limb that will be working hard during your exercise6
  • Record the results of how your blood sugar has been affected by exercise to inform future decisions
  • Adjust insulin amounts for the meal you eat before exercise and, potentially, change your basal insulin where appropriate. Your insulin requirements are likely to reduce following future exercise but any change to your insulin regime should be made alongside consultation with your diabetes care team
  • Stay hydrated. Too little liquid can cause blood sugar to rise due to dehydration, especially from sweat while exercising

As much as there are exercises that are argued to be more likely to cause either hypoglycaemia or hyperglycaemia, testing blood sugar before beginning physical exercise is crucial for making appropriate choices. Regular testing throughout is vital to understanding how your body responds to different types of exercise, especially upon initial diagnosis.7

Exercise that can cause hypoglycaemia

Hypoglycaemia occurs when blood sugar drops too low and causes a fast decrease in energy. This should be an immediate marker to stop and test during exercise. However, certain exercises are more likely to cause a drop in blood sugar than others.

As stated, continuous physical activity is most likely to cause a gradual drop in blood glucose. Should you suffer a ‘hypo’ before starting exercise, then you are more likely to drop into ‘hypo’ during it - be extra vigilant in this case and consider delaying the exercise until later in the day where possible.

Exercises more likely to cause hypoglycemia include:

  • Running
  • Cycling
  • Swimming
  • Hiking

Exercise that can cause hyperglycaemia

Hyperglycaemia, or when blood sugar increases to high levels, is most likely to occur after performing high-intensity exercises that rapidly increase heart rate. Research has shown that these exercises will most likely increase blood glucose for up to 2 hours post-exercise before blood sugar stabilises. Therefore, after performing a high heart rate exercise, blood sugar should be monitored closely. You could also consider taking a correction dose of insulin with some appropriate food or fluids for recovery afterwards.

Some examples of these exercises are:

  • Weightlifting
  • Sprinting
  • HIIT and other exercise classes
  • Gymnastics


Diabetes control has been shown to improve with the introduction of exercise and, indeed, is actively encouraged to help in the reduction of potential complications such as heart disease and stroke. Exercise leads to a longer and healthier lifespan, improves mental health, and has all round positive benefits for your body.

Health guidelines suggest doing moderate exercise for 150 mins each week, which can mean brisk walking or gardening. Alternatively, you can opt for something a bit more vigorous, such as running or playing sports for 75 mins each week. Better still, a mixture of the two is thought to produce the best results for your fitness and diabetes health. 


  1. Diabetes UK. Insulin and Diabetes [Internet].
  2. Fahey, A. J. et. al. The Effect of Short Sprint on Post Exercise Whole Body Glucose Production and Utilization Rates in Individuals with Type 1 Diabetes Mellitus. The Journal of Clinical Endocrinology & Metabolism. 2012 Nov 1;11(97):4193-4200:
  3. Juvenile Diabetes Research Foundation Ltd. Exercise and Type 1 Diabetes [Internet].
  4. NHS. Type 1 Diabetes - Living with diabetes - Exercise and Sport [Internet] NHS; 2021 Aug 6.
  5. Cockroft, E.J. Narendran, P. & Andrews, R. C. Exercise Induced Hypoglycaemia in type 1 diabetes. Experimental Physiology [Internet] 2019 Nov 30; 105(4):590-599.
  6. Roberts, A. J., & Taplin, C. E. Exercise in youth with type 1 diabetes. Current Pediatric Review, 2015, 11(2), 120–125.
  7. Hasan S, Shaw SM, Gelling LH, Kerr CJ, Meads CA. Exercise modes and their association with hypoglycemia episodes in adults with type 1 diabetes mellitus: a systematic review. BMJ Open Diabetes Research and Care [Internet]. 2018 [cited 2023 Mar 10]; 6(1):e000578.

Rick Ashworth

BSc (Hons), Psychology, The Open University, Milton Keynes, England
I'm a type-1 diabetic and ultra-endurance athlete, focusing on type-2 diabetes remission for life, not a 30-day intervention. Healthy is complication-free for life, dying of old age, not illness @thediabeticrebellion.com

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