# How long prior to exercising (running), should you test?



## Nadia Robertshaw (Oct 24, 2018)

My DN advised I should always test before doing exercise.

I’m just wondering how long before, and after people test? 

Obviously, I don’t want to be testing to late, but do t want it to be to early either.

I’d be most grateful if you can share your routine in order to give me some idea.

Thanks all


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## Matt Cycle (Oct 24, 2018)

I always test not long before I set off.  5 or 10 minutes and it gives you time to do something about it, i.e. whether to eat a snack or not.  Hopefully you will have an idea anyway whether you're low or high or not.  I also test when out but I'm often out on a 3-5 hour ride.  I'd certainly advise testing when back and then fairly frequently through the rest of the day at least to begin with.  This all depends on a number of factors such as length of exercise (e.g. 20 min jog compared to running a marathon), how strenuous the exercise has been, etc but it should give you an idea of how it's affecting you.  The thing to bear in mind is blood glucose levels can carry on dropping for the rest of the day and through the night after exercise as the muscles replace glycogen.  Again, different parameters will affect this - quick jog v marathon.  If you can get a Libre then it's ideal for this as you've got an instant check of what your bg levels are doing, even whilst you're running.


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## missclb (Oct 29, 2018)

Hi Nadia, the important thing is to know what the trend is. I have a freestyle libre, so I can see that with a quick swipe. Before I had that, it was a little trickier but not too bad. When scuba diving for example, I used to start testing an hour before, then half an hour then 15 mins then literally just before. Then i'd have a really good picture of any rises or dips. But that's over cautious, and understandable given the nature of the sport. 

For running or swimming, I would test maybe around an 40-60mins before I was planning to go, just to check that my levels were okay, then i'd test again right before. If the first test was too high, then i'd abandon my plans. I learned to time my exercise to when my levels are as steady as possible, ie no recent short acting insulin in my system or indeed food. I like first thing in the morning, or early evening before dinner (and no mid afternoon snacks!) for this reason. I definitely perform better when my levels are normal. 

It might be worth testing a bit more frequently (both before and after) to begin with while you see how you repond, then you can find the times that work best for you, and start to test less.


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