Before I had Libre, I used to target 7 or greater before going to sleep. I'm a T3c following a total pancreatectomy and so had extremely erratic BG behaviour, yo-yoing from low to high and rapidly back to low again.
Once I got Libre, I reduced that to 6 or greater, and at that stage I was on Levermir as my basal, taken twice daily. Because Levermir is a relatively flexible insulin I saw, from my Libre overnight plots, that sometimes my BG was steady during the night and sometimes I went mildly hypo. I couldn't work out why:
But I was regaining fitness and thus more active, on an irregular basis; so was earlier activity that day (or even from the previous day) causing BG falls?
Also my diet was (still is) very varied, so possibly some foods were digesting more slowly and thus continuing to release glucose while I slept, whereas on other nights digestion was (perhaps) complete before I slept and so was my basal too strong for that night?
Before I got to the bottom of this, I made 2 further changes. Firstly at my request my DSN switched me from Levermir to Tresiba, a less flexible basal taken once daily (8am for me). Secondly I found and set up the Diabox app which gave me Continuous Glucose Monitoring (CGM) along with better alarms than Libre. The consequence has been:
My basal, after a settling down period, is at present very steady during periods of fasting, eg while sleeping. (I am considering a 1/2 unit reduction as the warmer weather continues, but not just yet).
My improved monitoring by CGM and dual low alarms leaves me more confident in my monitoring so I feel much more content to go to sleep when my BG is 5+. Below that I eat a small biscuit, 5-6 gm; and if above 8 I take a small bolus correction targeting back to 6. I have the NovoEcho pen allowing 1/2 unit dosing.
So your question is very sensible (safe). The answer, in my opinion, initially depends on what your basal insulin is. If a shorter life basal such as Levermir, then your BG is possibly more susceptible to night time changes and thus a slightly greater margin of cover is needed while you sleep. And with Levermir some people choose to make regular changes to their basal dosing as part of their BG control. On a less flexible basal that control can only be done by bolus dosing (or snacks, as appropriate), since a basal adjustment takes 3 or more days to have an effect.
I'm afraid diabetes is complicated, confusing and contradictory. But with time and diligence it is possible to get some understanding and that experience helps you to judge what works for you. That said I still have stupid, inexplicable days! But I'm only 2 years into this new lifestyle.
