Hello i am Biagio from Italy, Milan.
In Italy we use a formula to tehoretically calculate factor of correctnes (that is how much blod sugar level dicreases with 1U of insuline)
1800/ total U of insuline (basal + bolus) by day
Mine is 1800/35 = almost 50
Of course best practise is test it, and i mean when i get a > 180 i do a bolus knowing that 1U will bring me at almost 130.
But , in doing that , i have to keep in my mind i much insuline i have "on board" from previous bolus.
Example if i get 180 after 2h from previous bolus, i use Humalog insuline and i know that i will have into body some residual quantity for other 2 hour so better not to do 1 full U but 0.5 are enough
In my opinion it's very important monitoring blood glucose level at lest before and 2h meals so to be able to correct values not in range.