Sports and Exercise can have a range of influences on the blood glucose levels before, during and after activities – the most important part first and foremost is to go in prepared, and to go in with all the passion you feel for the activities you love.

The initial core focus should be on the types of movements which take place during your exercise and in that lies the fundamental answers as to what might happen to your blood glucose during and after activity.

Aerobic activity is quite diverse. The mainstream meaning of it is on-going exercise, keeping a consistent pace. Marathon running is a good example, in moving for a long period of time and burning a continuous rate of energy. Walking is a different activity, it isn’t burning as much energy as rapid as when jogging, but the movement is similar – the same consistent movement – and this in most cases gradually lowers blood glucose levels. With jogging being more physically demanding than walking, it would be expected that blood glucose levels decrease more faster when running than when walking; however, nonetheless, with it being an aerobic exercise and continuous pace, both walking and jogging, it would be expected for blood glucose levels to decrease during activity.

A game of football, on the other hand, could well be deemed ‘aerobic’ too in exercise – as it goes on for a long period, usually 90 minutes – however, when you consider the types of movements, it is more of an ‘in-betweener’ as the changing of pace is more relatable to anaerobic movements. In a game of football you could be jogging at one pace and then the ball flies over and you change and burst into a sprint. The ball might go out of play and you start walking. You jog. You sprint… you change pace consistently. This may well alter depending on the position of the field you are playing and style of play you have – but in many cases the anaerobic aspect of football with the altering of pace causes blood glucose levels to increase during activity. Various sports, particularly team sports, have similar forms of exercise.

Aerobic movements, as reflected above, can cause spikes in the blood glucose levels. A sudden burst of energy can cause the liver to react and release stored glucose back into the bloodstream, which, in most cases temporarily, rises the blood glucose. Adrenaline is another factor which can spark this reaction.

It is not so much the sport itself which determines what happens to your levels – it is you, the athlete, and your movements and performance. Everybody is different and has their different ways, with different body masses, insulin doses and diets. So what is common is to see differences in blood glucose levels in those ‘centralised’ sports, like football, rugby or tennis, where you have a balance of aerobic activity in being active for a long period but altering your pace and movements throughout – but similarities in the ‘clearer’ activities, where those running marathons will decrease in blood glucose levels during activity, and those doing the power-lift in weight-lifting will spike up a bit.

Pre-exercise adrenaline, as mentioned above, can have a big say and cause levels to rise a bit higher. When performing in competitive sports in particular, we do not want to have in balanced blood glucose levels and having hyperglycemic bloods will cause difficulties in your performance as you can’t 100% concentrate. Post-exercise is a very interesting one. This does very much depend on your performance; your movements and levels of energy burned. It is not uncommon if taking on the extreme, such as marathon or triathlon / ultra-marathon running, to be at risk of a hypo not only during activity but post activity too. Furthermore, those sports which can spike levels during exercise such as the football, rugby, and even tennis games, contain a high chance of levels crashing lower post exercise.

5km running is a good example of the impact of movement. You could go out to work on your fitness and jog a distance of 5kms… and the chances are levels could drop a bit as it is not intense and it is a jog which burns energy at the same continued rate for a period of time. On the other hand, you could go out to beat a time or even more so, race – with the adrenaline factor that brings. And this can have the opposite impact on blood glucose levels to running the same distance in a different style, levels could slightly increase during the race. With both of those movements in mind, there is also a higher chance that the runner competing, or going at a more rapid pace, whose blood sugars may go up a little higher than the jogger, will decrease in blood sugars a bit more rapidly post exercise than the jogger too.

If we diagnosed Usain Bolt as a 100 / 200m sprinter with type 1 diabetes, the chances are he may spike during his activity – and of course with adrenaline with the atmosphere before a race – he goes from nothing to 100 mile an hour! It would cause a spike but not a major one in my estimations, as it is very quick, 10 seconds or so… so a brief spike upwards, more so pumped by the adrenaline factor, and because of that exercise being sharp but rapidly concluded, the chances are Usain wouldn’t crash in his levels too much afterwards either. Whereas someone engaging in activity for longer spells would be more prone to crashing in levels post exercise.

Cooling down after exercise, especially those glucose spiking sports, are beneficial towards easing that process down and preventing night time hypos. Without cooling down, there is a fair chance that levels could stay higher for longer and then crash heavier in the hours to follow. Nobody wants a night time hypo! So there is a great importance in being able to keep a check on blood sugar levels before, during and after exercise – and in that making the best decisions regarding both insulin and carbohydrate consumptions, the latter again before, during and after exercise. I might want some higher carbs in my system on a marathon morning, but perhaps not too great an amount on a football morning where my levels could increase during the game due to the movements- and then I might want a higher carb meal afterwards to help prevent the crash. By listening to your body, keeping on top of your diabetes and going in prepared – knowing those movements you are about to undertake – you can find the best answers for you.



Gavin delivered a great presentation to a packed house at the Minneapolis JDRF headquarters. Talking about his amazing accomplishments is a quick way to inspire people. Gavin openly shares the struggles he faces along the way (yet in a positive way) which is something everyone can relate to, no matter where they are on their diabetes journey. It builds a great connection between Gavin and his audience and brings his presentations to the next level.

Scott Johnson • Scott's Diabetes


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