I usually find if I go above 14 I need 1/3 to 1/2 as much insulin added to my normal ISF dose.
Also found different insulins didn't work well at high BGs - Fiasp was like injecting water above 12, where as Novorapid (Fiasp is Novorapid with 'stuff in') worked with the 1/3 increase.
Looks like...