It is used as an excuse by quack doctors (including naturopaths and "functional medicine" practitioners) to diagnose people with hypothyroidism even if all the

It is used as an excuse by quack doctors (including naturopaths and "functional medicine" practitioners) to diagnose people with hypothyroidism even if all the blood tests come back normal. Here is a good summary: https://hormonesdemystified.com/basal-body-temperature-and-your-thyroid-why-i-dont-care-and-neither-should-you https://hormonesdemystified.com/basal-body-temperature-and-y... As for the paper you linked, a correlation of -0.013 degrees centigrade is too small to be useful as a diagnostic tool.