Recruiting for Community Self-Experiment: How do Hot Showers Affect Blood Glucose?

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cross-posted to r/diabetes, r/diabetes_t1, r/diabetes_t2, r/QuantifiedSelf, and the Quantified Self Forum to recruit as many participants as possible.

We finished the study and just posted a final analysis of the data.

While we were not able to get firm answers to all of our questions, we did get a measure of the effect size and rule out it being a CGM sensor artifact (the leading hypothesis in the original post). We also learned a lot that will help guide future Community Self-Experiments.

Overall, we consider the experiment a success and plan to do more community experiments. The next one is a study to measure the effect of food ingredients and combinations on blood sugar (especially those used in low-carb diets). If you’re interested in joining in, let me know in the comments or send me a PM.

A few days ago, u/NeutyBooty posted on how hot showers caused their blood glucose to rise. Lot’s of commenters confirmed the general observation, but for some it appeared to be a CGM artifact, for some it matched their finger-stick meter, and others they see a BG drop.

I’ve been interested in self-tracking and experimentation for a while and this seems like a perfect opportunity for a communal self-experiment.

We currently have 7 Redditors participating from the original thread , but I’m hoping we can get even more people signed up so we can get a really great data set. Anyone’s who’s interested in participating, please comment or PM me.

The basic idea is to agree on a simple experimental protocol, each of us run the experiment, combine and analyze the data, and see if we can figure out 1) Is the shower effect real or a CGM artifact and 2) how does it vary from person-to-person?

The 7 of us organized and worked out the protocol using group chat and and a new subreddit, r/QuantifiedDiabetes. We’re starting the experiments and looking for more participants.

Here’s the details:

  • Background:
    • In u/NeutyBooty’s post on hot showers causing blood glucose to rise, lot’s of commenters confirmed the general observation, but for some it appeared to be a CGM artifact, for some it matches BGM, and for others they see a BG drop.
    • From my PMs, some of us have CGM’s, some have regular BGM’s, and some have both.
  • Questions to answer:
    • Is the “hot shower effect” a real change in blood glucose or an artifact of CGM sensors getting warm (or some other environmental change)?
    • What is the person-to-person variation in the magnitude and direction of the “hot shower effect?”
  • Protocol:
    • Pick a time when your blood glucose is relatively stable (no recent meals, medication, exercise, etc.)
    • Turn on the shower to the hottest temperature you’re comfortable with and let the temperature stabilize. If possible, measure the temperature (e.g. with an instant read thermometer).
    • Measure your blood glucose with both a CGM and regular finger-stick meter and record the data.
      • If you don’t have both types of meters, use whichever you do have (data will still be useful for the second goal)
    • Take a 20 minute shower.
    • As soon as you finish the shower, measure your blood glucose again with both a CGM and regular finger-stick meter and record the data.
    • Monitor your blood sugar for one hour (measure every 15 min. for finger-stick meter)
    • Record anything that might have affected blood glucose during the experiment.
    • Repeat the experiment multiple times (preferably ≥3, but any data is better than nothing) to assess within-person variability.
    • Post your data in a comment or PM to u/sskaye. I’ll compile it and make available to everyone to analyze
      • If you want your data to be anonymous, just let me know and I’ll remove all identifying info.
    • Optional variations:
      • Vary the time or temperature of the shower
      • Try a bath, hot tub, or sauna instead of a shower.
  • Data to collect:
    • For each glucose measurement: time, blood glucose, any important observations
    • General: whatever demographic info you’re comfortable sharing (e.g. male/female, T1/T2/LADA, age)

Haven’t done this experiment, but here are a few related observations I’ve made:

  • Taking brief hot/cold showers in the morning, or sitting in a sauna for a few minutes doesn’t appear to have an obvious impact on my blood sugar.
  • I usually also take a brief hot shower in the evening after exercising and drinking a milkshake. I skipped the shower once, and the blood sugar response to the milkshake appeared to be slightly worse.
  • I once took a 15min hot bath in the evening after eating ice cream. Surprisingly, my blood sugar staid completely stable throughout. Don’t know if this is an artifact* or “real”; I suppose you could take a bath while keeping the upper arm out of the hot water to find out…

* The chemical reaction CGMs rely on is temperature dependent, so they use a temperature sensor to correct the results. If the temperature goes too high or too low, no data is reported, and I wouldn’t be surprised if accuracy is reduced close to the limits.

Interesting! BTW, data has started to come in and, surprisingly to me, it looks like the effect is real and not a sensor artifact. Still need more data to be confident in the conclusion (worried about confounding effects from time of day, time since last meal, etc.), but the effect size is about the same for people using finger-stick vs. CGM.

Based on the effect size we’re seeing, ~14 mg/dL, I suspect non-diabetics wouldn’t see anything, but I’d be very interested to see the data if you were willing to try it.

Lastly, based on your and other’s advice, I spoke to my Dr. about getting a CGM. He prescribed a Dexcom and I’m working through the insurance issues right now. In the interim, someone on reddit shipped me some Libre sensors and I’m going to start using them in a few days. That should give me a lot more data to work with. I’m particularly interested to compare the accuracy & precision of the different measurement methods and figure out what’s going on with different foods on time scales longer and shorter than the standard 1 & 2h post-prandial time periods.

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That’s a really interesting effect! As part of our collective self-research project (see details in this thread) we have some people, including me, who are interested in doing self-research involving the use of Freestyle Libre sensors (see details and ongoing discussion on the forum).

Maybe you want to share your thinking there as well (and/or participate in the self-research project!)

Just posted a preliminary analysis using the first 22 measurements. If anyone’s interested, you can read about it here. We’re still looking for more experimenters, especially non-diabetics, so if you’re interested, let me know.

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We finished the study and just posted a final analysis of the data.

While we were not able to get firm answers to all of our questions, we did get a measure of the effect size and rule out it being a CGM sensor artifact (the leading hypothesis in the original post). We also learned a lot that will help guide future Community Self-Experiments.

Overall, we consider the experiment a success and plan to do more community experiments. The next one is a study to measure the effect of food ingredients and combinations on blood sugar (especially those used in low-carb diets). If you’re interested in joining in, let me know in the comments or send me a PM.

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