I wake up at the same time and eat the same thing every weekday morning. Still, my bg at noon will range from 3 to 12. This after having this thing for 17 years

I wake up at the same time and eat the same thing every weekday morning. Still, my bg at noon will range from 3 to 12. This after having this thing for 17 years. Yeah, it's hard. Edit: On the 42 factors, during-sleep BG is either stable or up. For me it's either side or down (but occasionally up). I do have the 'pre-sleep' BG that usually goes down, right after brushing my teeth (is it post-brushing then?), which is a well-known factor on Reddit. Basically, doesn't matter if I'm going to sleep at 10pm or 1am. I check my BG, it's 8, arrow straight or even up (CGM indicates the trend). Brush my teeth and check again, 7 with arrow straight down to the floor :/