Morning Basal Test

This morning I did a basal test.My last one was on the 8th of January.It was successful,but this time I dropped from 6mmol at 7am to 2.7 at 11am.I really don’t understand what could make it change so much.I reduced my 7am basal rate and will try it again.I know John Walsh’s book says to change the basal rate 4-8 hours before the low or high occurred.Is that accurate or does it work faster? I was changing my rate the hour before.I also did a nighttime basal check with success.I have had no lows in the past 24 hours.

I wish this thread didn't go unanswered.