I’ve had this experience more than once with 24-48 hour fasts, and it’s very puzzling. Maybe some old hands here have a theory?
I eat ketogenic routinely, so when I start a weekend fast, my BG is around 90 and I blow around 12 ppm on the Ketonix meter. After being fasted for 36 hours (just water, salt, a mug of bone broth and splashes of heavy cream in my coffee) I find that the BG is 115 and Ketonix says around 5 ppm! In other words, fasting seems to take me lower on the ketosis range! That seems to be just weird to me… How is that even possible?