Blood sugar levels

Hi, as far as I know I don't have diabetes, but I went for a finger-prick test at my pharmacy as I think i have mild acanthosis nigricans around my armpits and beltline. I read this can be caused by insulin resistance/pre-diabetes.

My reading was 5.7 which i was told was high end of normal. This was just over 4 hours after last eating(large meal).

I was offered another test next week first thing in the morning to get an 8 hour fasting level but just wondered if 5.7 was normal or not 4 hours after a meal, or if this could be a sign of insulin resistance. How long after eating do glucose levels return to fasting baseline?

Thanks for replies. I will get the fasting test next week and take it from there.

@sparkyrich, the markings on my skin have been there for years (around 5-6 years) and appeared during a time I was very overweight - over 18 stone.
I am aware Acanthosis Nigricans can very rarely be as a result of cancer but when it is, from what I've read, it usually appears suddenly and quite severely.
Mine (if that's what it is) is very mild and has been there for years, without much if any change and conincided with a time I was very overweight. I also got skin tags under my arms at the same time which are linked to insulin resistance.

I wasn't actually aware of Acanthosis nigricans until earlier this year, prior to then I just thought the marks under my arms were pretty normal due to friction/chafing, which is why I never considered visiting a Doctor. It's only after reading a lot about it and seeing pictures of it, that I thought this may be something I have albeit a very mild case, and makes sense given my history of overweight.