Why Does my Blood Sugar go up when I Exercise?

This is not true for me… I plummet. Consistently. Predictably. Someone in my group was looking for answers though, and although I don’t have any, I know where to come for them…

All I know is that she rises with exercise, always has, and has never figured out why. I’ll see if she will come around, but I’m willing to deliver some general info to her first…

If she really wants to get into it, she should come and have direct communication with the master.

Otherwise - how interested is she really?

But hey. That is just my opinion.



Interested enough to say she’s always seen it but never understood why it happens… and to ask if anyone else has ever experienced it. Yes, I thought of Eric (assuming this is the master you speak of), but I wanted to return to her with a link. I believe there are probably articles in here somewhere she could read… if someone could point me to them.

And a good one it is. :grin: I’m just bridging… I come across questions to which I know WHERE to find the answers. It’s a matter of bringing them together.

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As if there was any doubt?



Really. For the difficult exercise questions. I have seen @Eric getting into it and the back and forth. If she really wants help, she should come here and spend some effort and let him help her. But then again the reality is that everybody does not want help and sometimes they are just looking for comfort. Everybody is different.


Well when you said “master” I thought there might be someone else. :grin:

Totally agree. And I put that out there, too. Yes, sometimes we would like to know but don’t really care enough to spend the time. Her question came up as part of a thread over there though where someone else might be able to use the info, too.

I have found, since now I feel like I should explain my behavior, that people are reluctant to come over just on merit alone. I can tell them what a great place this is, and they can say how great it sounds, and then something—probably life— happens. If I bring them a relevant link, they are just a click away from incredible information. And charming conversation. :grin:

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If I remember right, really high-intensity exercise raises BG because the stress hormones cause the liver to dump glucose. The threshold was something like heart rate above 90% of max. Long-duration exercise will drain out “all” the glucose from the bloodstream, so this spike is more of an acute thing.

I’ve heard of a trick for temporarily fixing a low by running a half-dozen wind sprints.


I think this may have been debunked… or at least it may not work quite this way. I had read in JDRF article that a couple of sprints (they may have said just one) at the end of a long workout was enough to stop post-exercise hypoglycemia. So I was sprinting down the street at the end of my runs… and causing great alarm in all the neighbors. :grin:

I THINK this is what Eric just had me ask my cardiologist about… I get in the majority of my workout at greater than maximum heart rate, but I still crash 10-15 minutes into workouts. When I used to do Zumba, my heart rate was nearly almost at 200, and I’d drop 10 minutes in without exception.


It really varies on how well-conditioned you are, as to how much of a sprint you would need to raise your BG. You can definitely raise it, if you do it hard enough and for enough duration.

The best thing to look at is heart rate and duration at that elevated heart rate, not speed. Because speed will vary based on how tired you are.

I know exactly what heart rate will spike me, and how much. It’s useful to know.

I have discussed this many times on the site. Here is a link that kinda explains it.

Basically, at high intensity levels, the spike is just the body’s natural response. It’s a typical “fight or flight” response.

If you are being chased by a tiger, your body would want to make sure it does everything it needs to escape. So your body releases hormones - epinephrine (adrenaline), norepinephrine, and cortisol. Your heart rate and blood pressure increases. The oxygen that goes to your tissues increases. And your liver releases glycogen stores to give your body fuel.

Everything that is happening with high-intensity runs is the same as it would be for a non-diabetic. The only difference is that the non-diabetic doesn’t see their blood sugar spike because their pancreas automatically releases insulin for the extra fuel from their liver glycogen.

And it might not really be a fast run that does it. You might have a significant increase in your pace:heart rate ratio on a long slow run, if your pace is greater than your fitness level.

For example, if a 10 minute pace is tough for you, you might not spike after 1 or 2 miles at that pace, but after 5 miles your heart rate will have increased a lot more than it was early in the run. And that might be enough to do it. So it might not seem like a “fast” run, but the heart rate increase over the length of the run is enough to cause an eventual spike.

Also, it might be that this whole conversation is not even relevant - maybe it is because they are turning off their pump for the whole run, or taking a bunch of sugar before hand, and that is causing the spike.

All of that is to say, that’s why short little pre-canned answers may not be what your friend needs. It takes a little bit of back-and-forth with someone to really give them the best answer that applies to them.

So you can give them canned answers, but the best answer for them will be after an exchange of info.


And I’ll hand it all to her along with that piece right there. Just bridging…


Great info. Thank you.


@mattie, do you go up, too?? I didn’t know that…

I find that my BG will generally go up during yoga classes in which we hold poses longer with a lot of active muscle engagement. On the other hand, flow classes (moving through pose sequences on the breath) definitely drop my BG. So I have to prep differently in terms of temporary basal rates, starting BG and pre-class BG trends, and carbs needed (if any). And then sometimes I end up having to change things up at the last minute ‘cos the teacher is trying something new or there is a last-minute substitute teacher. And of course I always have quick carbs handy! :woman_in_lotus_position:t3::lollipop:


Here is my rookie experience:

Yoga - drops
Spin - flat, to small uptick
Resistance Training - spike


You and @CatLady are blowing my mind with the yoga bit. I feel like yoga shouldn’t do much of anything… it’s gentle, meditative… that’s interesting. Though I do understand how different kinds could have different turnouts… so much for a nice, relaxing yoga session. And spin??? Mild uptick? really?

I am a very predictable type… 10 minutes into almost anything and I begin to crash. I know this will make you cringe, Eric, (if you’re reading), but I used to run my numbers up to a 300+ so that I could get through a workout. Even then I’d end up doing tabs… Those were the days when a 200 was considered a crash…:roll_eyes:

That’s what DM used to do too. But not anymore.

@daisymae, tell her about it.

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I used to aim for 150 or so before lawn mowing or marathon housework and then keep eating cookies! With @Eric’s help, I am steadier…and my cookie consumption has dropped. :smiley_cat:

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i used to do this exact same thing. i would eat a UCAN protein bar and wait for my BG to get up to 200, then i would swim for 2 hours and my BG would drop down to 60. then on my walk home i would spike again.

now, i turn off my pump 2.5 hours before i exercise with no IOB left-over from bfast, and then i go to the pool. generally i am around 120 when i jump in (sometimes 80, sometimes 130) and i swim in 1/2 hour intervals, just getting out to do a finger-stick and to see if i need to take any glucose tablets. then i jump right back in and continue swimming. i do a 90 minutes swim and remain basically on a flat line, finishing up at around 85. then i bolus for a portion of the basal insulin i missed when i turned off my pump, and i dont spike at all. i remain flat.

then i bolus for 50% of my carbs/protein shakes that i drink 1/2 hour after finishing my swim. by dinner time, i am ready to refuel with high carbs and high protein.

i used to be afraid of all of the carbs, but my last 3 A1cs were 4.9%, so i am no longer concerned about stuffing my face. i eat what i want and i swim without going either high or low. its wonderful.

read about my experience on “Daisy Mae’s Swimming Thread” and you’ll see all about it as it unfolded. hopefully, it wont take you as long as it took me to get where i am today. :blush:

best of luck. enjoy!!!


Nice !!!


Here’s my experience:
Active outside for hours- slow drop
Running 2-4 miles- steady (almost never up or down)
Kickboxing for 1 hour- Steady if I’m lucky but it usually rises a little to a lot. There are several times where I’ve gone up 100 or more mg/dl in that 1 hour. Adrenaline & spiking HR makes all the difference for me. I’ve started taking insulin before class if I’m not too low to take the edge off these spikes.