I've seen the same thing. My A1C actually went up on low carb from 4.9 to 5.6 which really surprised me. It's still considered normal but equates to an average daily blood sugar of about 100 which is higher than I want. I too was surprised. I'm not sure what caused my A1C to go up, but I suspect it was one of two things. Either I'm losing blood sugar control or more likely I was having a lot of high/low swings and it has now evened out, just a little higher than I thought it would.

I have Dr. Bernstein's diabetes book, and its based on his statement that A1C levels should be even lower that I give this any thought at all. He lists some supplements and approaches to try before going on meds. I don't remember it all but I think alpha lipoic acid was one of them. I'm going to try his suggestions and see if that helps.

5.3 isn't bad - just higher than you'd expect.