When and why are the same for me Shoshana. Every couple of weeks I look at the downloaded data from my pump & CGM. If I see a pattern of highs or lows, I generally change my basal rate (less often my I:C ratio). Sometimes my needs change seasonally. If I'm sick I need to raise my basals as well.

i meant how many different basels do you have during a 24 hr. period? i'm just curious.

i only lower the basal when i walk a lot.otherwise i don't touch it.

in a 24 hour period, i have 3 different basal rates:)