High blood sugars with strenuous exercise

I have the same issue. Yesterday, I skipped breakfast and went for a run and my blood sugar went to 14 or so. This is when fasting!

Same here, from any exercise at all. Just the way some of us are made.

Same for me although most of the time not up to 14. It is somewhat of a known phenomenon, if you exercise lightly (walking) your BG goes down, if you exercise hard it goes up. Just your body reacting to the need for energy and yes it will use any available glucose from the liver and muscles first before switching to fat burn or if you really working hard anaerobic mode.
For me as a T2 this means that after 45 minutes to an hour+ my BG goes down pretty steep to a normal level again.
Don't know how a T1 should handle this though.

Emmaline said:

I'm in my sixties and a member of a bike group where we cycle for 2 hours (also eat very little carbs). One of my frustrations is having really high blood sugars during and after a ride. It takes a long time for them to reduce which leads me to think I'm having glycogen dumps on the ride? Does anyone have tips for avoiding this? I find stopping the ride to deal with this really tricky!

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Here is a somewhat nerdy thread on my experiences. Long posts and lots of meandering off topic though: https://www.diabetes.co.uk/forum/threads/going-high-with-exercise.196324/

The advantage of having Type 1 is that you can use procatively insulin to help with your BG rise.
I find my levels rise when I climb if I don;t give myself extra insulin.
I prepare by giving myself enough fast acting insulin to lower my levels to 3 under normal circumstances but with he exercise stress, they stay in range for a few hours.

EBe66 said:

Same for me although most of the time not up to 14. It is somewhat of a known phenomenon, if you exercise lightly (walking) your BG goes down, if you exercise hard it goes up. Just your body reacting to the need for energy and yes it will use any available glucose from the liver and muscles first before switching to fat burn or if you really working hard anaerobic mode.
For me as a T2 this means that after 45 minutes to an hour+ my BG goes down pretty steep to a normal level again.
Don't know how a T1 should handle this though.

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My FBG goes up even after light walking, like 30 or 45 minutes. I don't do anything really strenuous, not even incline walking. It is so frustrating

I cycle. It depends. What time of day are you going out @Emmaline, do you eat/dose beforehand, do you reduce basal at all?

If I ride hard my blood sugar will go up, though not vastly high just because of that, if I ride less hard it will drop. Once I've been out for some number of hours it will drop irrespective. The confounding factor is that if I go out first thing and eat breakfast without cover (as I have dawn effect these days) I will go very high, so I need to take some bolus to cover that (judging how much is the ongoing experiment!) OTOH If I go out at lunchtime, for example, I can eat some lunch (say 35g CHO) without bolus cover and only head into the low teens before trending back down.

My doctors have always told me that intense exercise is very good for diabetics and that my morning runs are a good thing. Because I only finger-prick tested 2 hours after eating, my doctors could never have known that I have blood sugar spikes when I exercise. Their advice was based on research showing that intense exercise has proven benefits. We don't need to worry if new tech like CGMs shows that we produce lots of blood glucose while exercising. The proven benefits of exercise still apply.

I can't see any downside to carrying on with exercise. I see big risks to becoming more sedentary. So I'm going to carry on regardless of the blood glucose spikes.