• Guest, the forum is undergoing some upgrades and so the usual themes will be unavailable for a few days. In the meantime, you can use the forum like normal. We'd love to know what you think about the forum! Take the 2025 Survey »

Can exercise cause short term spikes in BG?

miahara

miahara

Well-Known Member
Can exercise create short term spikes in BG, before lowering it? My normal average pre-lunch BG is around 6.6mmol and seldom above 6.7. Today after my LCHF breakfast I went out on a 22 mile bike ride – a fairly hard one involving some serious hill ascents.

When I got home I thought I’d test my BG to see how the exercise had lowered it, but much to my surprise it was 7.1. I think my maximum ever has been about 6.9 before lunch.

I ate about 45 minutes later – a low carb lunch of celery soup and a couple of thick streaky pork slices.

Two hours later I tested expecting my BG to show its normal small rise but to my great surprise it had fallen to 5.7, my ‘normal’ post-prandial BG is in in the 6s.

Any suggestions?
 
Last edited:
Yes. Intense exercise releases adrenalin, which raises blood sugar. This explains the "spike" to 7.1.

Exercise activates GLUT4 receptors, with is an alternative route for glucose to get into cells, and burns off glucose in the muscles and liver, meaning any glucose in the blood will be quickly being siphoned away to restock liver and muscles. This explains the lower readings after lunch - the GLUT4 receptors can remain active for hours after exercise.
 
So sounds like an initial spike as the body gets used to the fact you're exercising, and then it brings it down quite quickly afterwards as your glucose finds extra ways to get into the muscles crying out for it?
 
miahara said:
Can exercise create short term spikes in BG, before lowering it? My normal average pre-lunch BG is around 6.6mmol and seldom above 6.7. Today after my LCHF breakfast I went out on a 22 mile bike ride – a fairly hard one involving some serious hill ascents.

When I got home I thought I’d test my BG to see how the exercise had lowered it, but much to my surprise it was 7.1. I think my maximum ever has been about 6.9 before lunch.

I ate about 45 minutes later – a low carb lunch of celery soup and a couple of thick streaky pork slices.

Two hours later I tested expecting my BG to show its normal small rise but to my great surprise it had fallen to 5.7, my ‘normal’ post-prandial BG is in in the 6s.

Any suggestions?
Click to expand...
Don't worry about it! This is a normal physiological response to intense exercise you will get a drop a while later....seen by your 5.7 glucose.

For more detail see the Glut -4 answer

The body's physiology is a wonderful

Hope this is reassuring....
 
Exercise is a funny thing!
I've almost been tempted to stop because of the headache it gives trying to work out how to adjust my insulin but I'm getting there slowly with lots of logging and comparing!
I'd be happy with your readings @miahara (mine are much more extreme!) but we are all different and have different goals.
Generally speaking aerobic/cardio exercise makes me drop and anaerobic exercise makes me rise then drop. I also find as I'm getting to mange the during and after levels it's the following morning or even 48 hours after where I drop.
 
Was too low to swim this morning (2.7) thanks to yesterday lunchtime's full-on weights session and swim. Have been having a look at this thread as I'm staggered at how long the effects of exercise are lasting these days - I've been ramping up my training and it's made a huge difference.

I've not been above 6 all day (which without the unpredictability of the exercise factor I would normally take great pleasure in, don't get me wrong), having been sub-3 all night, but to be honest I'm feeling massively 'hypover' (with a hypo hangover) even now and am longing for my sofa.........

I need to get more au-fait with identifying the start of the steady drop so many hours after exercise, and setting alarms and temp basal rates for overnight and the next morning. It's just every session's different, and sometimes if I dip low after supper it can be due to a carb counting miscalculation from my mealtime bolus, and I have sometimes misidentified a drop like that as 'oh right, that's the exercise kicking in' and then dealt with the low then and NOT adjusted my nighttime basal because I think I've already dealt with the post-exercise hypo!

#seesaw #hardtopredict #feellikeanovice #hypostacking

FullSizeRender.jpg
 
I love that term hypover @Snapsy!
I was feeling it on Sunday, just couldn't get out of bed to go to the gym as I was 2.7 too.

Annoyingly last night I did spin... relatively good maintenance of my BS before and after then I ate and was still in range going to bed. I was high over tonight and today I've hypo'd twice. Grrrr!!
 
miahara said:
Can exercise create short term spikes in BG, before lowering it? My normal average pre-lunch BG is around 6.6mmol and seldom above 6.7. Today after my LCHF breakfast I went out on a 22 mile bike ride – a fairly hard one involving some serious hill ascents.

When I got home I thought I’d test my BG to see how the exercise had lowered it, but much to my surprise it was 7.1. I think my maximum ever has been about 6.9 before lunch.

I ate about 45 minutes later – a low carb lunch of celery soup and a couple of thick streaky pork slices.

Two hours later I tested expecting my BG to show its normal small rise but to my great surprise it had fallen to 5.7, my ‘normal’ post-prandial BG is in in the 6s.

Any suggestions?
Click to expand...
Maybe the rise after the bike ride was down to your running out of available glycogen before the end, so you liver helpfully released some to fuel the rest of it. I am finding something similar - if I go on fasting too long between meals, my nice low post prandial bg is replaced by a higher one, which is annoying when I want it to be low pre-prandially. I am resolved to experiment with eating eg a little cheese whenever a meal is going to be postponed. The second half of your puzzle is more difficult, but just maybe most of the 7.1 was used to replenish your muscles after their exercise, leaving a debit balance which was filled by the low carb lunch, so there was less surplus than usual 2 hours later. Bearing in mind that given the inaccuracy of meters the difference between 6.9 and 7.1 is not huge.
 
I think any rise in the short term provided it is not excessive is a worthwhile, due to the up to 48 hour benefit of improved insulin response, better blood glucose on the come down, usually circa 2 hours. Not to mention improvements in trigs, weight maintenance and general health.

You might consider including some weights, as the more muscle mass, the greater the GLUT4 uptake (which is independent of insulin).
 
Back
Top