Type 2 Hot Showers and affect on Blood Sugar

Does your BG rise or does the heat of the shower affect the readings from the sensor?
I ask because I notice a spike on my CGM graphs when I have a shower.
This is a true spike - up and back down again.
If my BG really rose, I would need insulin bring it back down again so have concluded that the spike is a CGM anomaly,

If you are showering as soon as you get up and your Libre is showing your BG rising and staying there, it could be a Foot on the Floor response - liver dump of glucose to start your day.

I reckon it is an effect on the interstitial fluid that registers on the Libre, or the sensor itself. I have noticed this pretty much every day for the whole time I have been using Libre (4 years?), but since I started using the Dexcom One+, 3 months or so, I have not seen the spike at all. This would suggest it is the Libre that is effected or Dexcom have programmed around it.

HTH

Yep, goes straight up and straight back down for me. If I wasn't wearing a libre I'd never notice it it's so quick.

Yep, happens to me as well. Got a Dexcom ONE+ CGM and it always rises after a hot shower. Don’t understand it really.

Effect in the interstitial fluid - good observation @barrym

Was going to pop in to say that I use a sauna blanket - my thought was that I could use it to raise my metabolism (theory was that while fasting I could use it to encourage more fat to be drawn out of my liver, but it's a stretch, even for me). I still think that's a thing, but honestly it's just fabulous to use, and I have no idea whether it affects anything at all..

As I write, I realise that the entire point of a sauna is to affect core temp, where a shower will not, so it's kind of moot...

but, warming up your interstitial fluid - that makes much more sense..

Something about interstitial fluid pressure rising with the stimuli of hot water??


If it has gone up then dropped toweling off on the graph? I leave well alone.

If it rises & stays there.. I do a correction dose before leaving for work.

Yes it's real (noticed it on finger sticks too) - another one to add to the Dawn phenomenon and feet on the floor syndrome. I need about 6 units before breakfast for all of these!

Jasmin2000 said:

Yes it's real (noticed it on finger sticks too) - another one to add to the Dawn phenomenon and feet on the floor syndrome. I need about 6 units before breakfast for all of these!

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I see meters more like a speed trap?
CGMs closer to a "dash cam." ( which due to GPS notes in linear time what speed at the time.)
I wish these sensors were around decades ago.. Hey ho..!

Jasmin2000 said:

Yes it's real (noticed it on finger sticks too) - another one to add to the Dawn phenomenon and feet on the floor syndrome. I need about 6 units before breakfast for all of these!

Click to expand...

So you get an actual BG rise rather than just the CGM producing a higher number, that's certainly interesting?

My libre2 spikes up when I have a (hot) shower, but then drops back down as soon as I get out - afaiu this is not a change in my actual BG but rather the sensor misreading due to either higher interstitial flow, or a temperature calibration issue. I've never seen my actual BG remain raised (once the CGM would have dropped back down) post-shower.

One interesting thing that's not been mentioned is that hot showers and baths can actually produce (real as well as CGM apparent) lower BG due to increased blood flow to peripheral tissues where insulin has been injected. I seem to remember from reading about this that it tends to happen to people who have lipohypertrophy (i.e. lumps) which would normally significantly delay absorption.

SimonP78 said:

So you get an actual BG rise rather than just the CGM producing a higher number, that's certainly interesting?

My libre2 spikes up when I have a (hot) shower, but then drops back down as soon as I get out - afaiu this is not a change in my actual BG but rather the sensor misreading due to either higher interstitial flow, or a temperature calibration issue. I've never seen my actual BG remain raised (once the CGM would have dropped back down) post-shower.

One interesting thing that's not been mentioned is that hot showers and baths can actually produce (real as well as CGM apparent) lower BG due to increased blood flow to peripheral tissues where insulin has been injected. I seem to remember from reading about this that it tends to happen to people who have lipohypertrophy (i.e. lumps) which would normally significantly delay absorption.

Click to expand...

Would you say your spike is the reverse of a "compression low??"

Jaylee said:

Would you say your spike is the reverse of a "compression low??"

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Yes, my response looks pretty much like that.

SimonP78 said:

So you get an actual BG rise rather than just the CGM producing a higher number, that's certainly interesting?

My libre2 spikes up when I have a (hot) shower, but then drops back down as soon as I get out - afaiu this is not a change in my actual BG but rather the sensor misreading due to either higher interstitial flow, or a temperature calibration issue. I've never seen my actual BG remain raised (once the CGM would have dropped back down) post-shower.

One interesting thing that's not been mentioned is that hot showers and baths can actually produce (real as well as CGM apparent) lower BG due to increased blood flow to peripheral tissues where insulin has been injected. I seem to remember from reading about this that it tends to happen to people who have lipohypertrophy (i.e. lumps) which would normally significantly delay absorption.

Click to expand...

Yes, I get a BG spike about 5 min after getting hit by hot water (about 2 mmol/L) and CGM rises likewise. Both remain high unless prebolused. I'm assuming its the work of those stress hormones, cortisol, epinephrine and glucagon.

Jaylee said:

I see meters more like a speed trap?
CGMs closer to a "dash cam." ( which due to GPS notes in linear time what speed at the time.)
I wish these sensors were around decades ago.. Hey ho..!

Click to expand...

I see meters like an informed journal.
CGMs are closer to a virtual reality complete with fake news and the promise of algorithmic paradise.
Hopefully they will be more useful by the end of the decade.

I don't think a hot shower or using the sauna has any real impact on one's BG level. My assessment of the apparent rise in BG is more a case of the electronics embodied in the sensor not liking the heat,and therefore stop working properly in that environment.

Jasmin2000 said:

I see meters like an informed journal.
CGMs are closer to a virtual reality complete with fake news and the promise of algorithmic paradise.
Hopefully they will be more useful by the end of the decade.

Click to expand...

We're all different, but I'm very thankful to have a cgm provided free by the nhs, and find it almost always either very close to or exactly the same as finger prick tests. Having had type 1 for decades, I'd hate to be without a cgm now.

Jasmin2000 said:

Yes, I get a BG spike about 5 min after getting hit by hot water (about 2 mmol/L) and CGM rises likewise. Both remain high unless prebolused. I'm assuming its the work of those stress hormones, cortisol, epinephrine and glucagon.

Click to expand...

Do you always have a shower in the morning? Do you think the BG rise might in fact be due to dawn-effect foot-on-the-floor (with an additional apparent rise in the CGM, potentially for other reasons re calibration, etc.)? I could imagine that getting in the shower first thing might well be the kick that starts the stress hormones going. My dawn effect foot-on-the-floor doesn't register for about 10min after getting up (on the CGM, so it is probably actually happening as soon as I get up.)

I don't have a shower straight after getting up these days - I usual need to persuade/drag my children from their beds, chivvy them into getting ready and then drive them to school, and then am either WFH, so tend to either do some admin so I know what's coming or sit in a 9am meeting if one's scheduled. If I'm going to work I tend to ride my bike so don't bother with a shower before leaving.

As I tend to have a shower later in the day (lunchtime after an exercise loop on the bike if WFH) or at work/in the evening if doing my cycle commute, this means there's no dawn effect/foot-on-the-floor in progress so I see that my CGM rise (though I accept we're all different of course!) is transient. I suppose it's possible my actual BG is also rising then falling rapidly back to where it was by the time I'm dressed. If I remember I'll try to stick my hand out of the shower and do a blood test one day to see what it says, though like you the CGM rise is only on the order of a couple of mmol/l so how easily I'll be able to pick that out of the usual noise is hard to tell.

Edit: changed "dawn effect" to foot-on-the-floor -> not enough coffee before writing the post!

SimonP78 said:

Do you always have a shower in the morning? Do you think the BG rise might in fact be due to dawn-effect (with an additional apparent rise in the CGM, potentially for other reasons re calibration, etc.)? I could imagine that getting in the shower first thing might well be the kick that starts the stress hormones going. My dawn effect doesn't register for about 10min after getting up (on the CGM, so it is probably actually happening as soon as I get up.)

I don't have a shower straight after getting up these days - I usual need to persuade/drag my children from their beds, chivvy them into getting ready and then drive them to school, and then am either WFH, so tend to either do some admin so I know what's coming or sit in a 9am meeting if one's scheduled. If I'm going to work I tend to ride my bike so don't bother with a shower before leaving.

As I tend to have a shower later in the day (lunchtime after an exercise loop on the bike if WFH) or at work/in the evening if doing my cycle commute, this means there's no dawn effect in progress so I see that my CGM rise (though I accept we're all different of course!) is transient. I suppose it's possible my actual BG is also rising then falling rapidly back to where it was by the time I'm dressed. If I remember I'll try to stick my hand out of the shower and do a blood test one day to see what it says, though like you the CGM rise is only on the order of a couple of mmol/l so how easily I'll be able to pick that out of the usual noise is hard to tell.

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Good thinking - did the same to verify BG rises. In the morning it's impossible to clearly separate Dawn Phenomenon (before getting up) from Feet-on-the-Floor (for me about 45 min after getting up) and the early shower comes in between. But like you I've separated the variables by showering at different times of the day and I always get a spike (best ones at midnight when I can drive BG from 5 to 9 if it's hot enough (and the CGM can't handle it and hits 11-12 before coming back down - so much for predictive algorithms!). So your CGM rise with a later shower should be paralleled by a BG rise.

ah, I meant foot on the floor, will correct my post. I'll also report back on whether my BG has risen mid-shower!