A1C and Hypothyroidism

I just got an A1C of 6.1 for the first time. I've never had issues before and the sudden increase from the year prior threw me for a loop. I've gotten a glucose monitor and have used it for several days but have never gotten a reading higher than 145, which was one hour after eating. Fasting sugars have all been under 100 and when I check two hours after eating they are always lower than 140 which seems to be in the normal range. I have read that hypothyroidism can cause a false A1C reading and I'm beginning to wonder if that may be the case. I'm planning on watching my sugar levels until I retest in 3 months but wondering if the blood sugar numbers remain normal do I have to be concerned about the A1C?