> A hot bath or shower can raise (then lower) BGL.
I suspect the author has come to this conclusion from CGM data, and therefore also that it is wrong (or at least not a very significant effect).
I also have T1D, and CGMs like Freestyle Libre (and probably also Dexcom) includes a temperature sensor and adjusts its readings based on the external temperature to increase accuracy. I think the changes in blood sugar levels during hot showers (etc) is probably due to the sensor not adjusting quickly enough to the rapid change in temperature, and not a physiological response.
For example, if I go directly from room temperature to my cold balcony, the CGM value will immediately make a huge jump upwards with the next reading, but then quickly revert back down again within the following readings. Considering the 15 minute lag time between plasma glucose and the interstitial readings of the sensor, its unlikely the sensor is immediately measuring a change in plasma glucose – it's simply (over)reacting and adjusting to the new temperature (since the thermometer won't have such a long lag time).
Very hot environments, such as a hot sauna, also makes my CGM readings completely inaccurate.
Hm, I finger-prick test and have definitely noticed that getting in a spa or hot tub can do pretty serious things to my BGL. My hypothesis is that if I have any insulin-on-board, that the increased bloodflow causes it to be taken up more rapidly. I think this might include lantus.
Another thing you have to be careful of: pressure on the sensor can drastically effect readings. This is particularly a problem if you sleep on your sensor.
According to [1] the G6 at least measures skin temperature, but it is unclear if it measures air temperature as well (which the Libre does). I also found a reddit thread [2] that indicates it's quite common to get drastic changes in readings during hot showers with Dexcom (probably G6 version based on the date), so you might be an outlier in that regard.
I suspect the author has come to this conclusion from CGM data, and therefore also that it is wrong (or at least not a very significant effect).
I also have T1D, and CGMs like Freestyle Libre (and probably also Dexcom) includes a temperature sensor and adjusts its readings based on the external temperature to increase accuracy. I think the changes in blood sugar levels during hot showers (etc) is probably due to the sensor not adjusting quickly enough to the rapid change in temperature, and not a physiological response.
For example, if I go directly from room temperature to my cold balcony, the CGM value will immediately make a huge jump upwards with the next reading, but then quickly revert back down again within the following readings. Considering the 15 minute lag time between plasma glucose and the interstitial readings of the sensor, its unlikely the sensor is immediately measuring a change in plasma glucose – it's simply (over)reacting and adjusting to the new temperature (since the thermometer won't have such a long lag time).
Very hot environments, such as a hot sauna, also makes my CGM readings completely inaccurate.