I’ve been on one cup a day, which I drink at 7:00am, for a week. Although many places on the World Wide Web will tell you that caffeine will negatively affect the diabetic’s blood glucose levels, cutting back on coffee has not helped me. My levels are still in the same zone.
This wasn’t the reason I cut back of course. I was more concerned in getting good sleep, but I was hoping for a little side benefit with the blood sugar. I wasn’t expecting anything that significant and pretty much thought I’d see no reduction in my glucose levels. Oh well!

I suppose at some point I will cut out the coffee completely for a week or so and see if that has an effect, but I’m not holding my breath. Moreover, because coffee has a myriad of health benefits, I have no desire in giving it up completely.
For me, keeping with keto and occasionally dipping back into paleo is the right path for me to keep my diabetes in check. The best thing for my blood glucose is fasting and a strict keto diet.
For those of you who don’t know, here are some of the benefits of coffee:
https://www.healthline.com/nutrition/top-13-evidence-based-health-benefits-of-coffee#section9
Of course, this is in moderation, I don’t think anyone is advocating you smash ten 8oz cups a day…which I was doing at my peak.