I went cold turkey too, and saw very good results within a short timescale on meter checking, though Nursie was scornful ("we don't take any notice of that") until I had my second 3-month blood test, the first having included my hospital stay when food was high carb (and would have been high sugar had I eaten those parts of it). By the second 3-month test, I was in the pre-diabetic range, and I hope to improve on that by the time of my next test at the end of Sept/beginning of Oct.
For me, progress was/is not linear, and I met with a series of plateaus, though have been totally strict with my keto diet. Currently, because (I suspect) of extreme heat, I am in the 6s though previously was in mostly 5s and sometimes 4s. It will be interesting to see what happens when the heatwave finishes. We are dynamic beings, and survival does depend on reacting to circumstances, not just mentally but physically too.