A non-diabetic A1c is 4.5-6% (26-42).
Ideally, this is the range that people with diabetes should be aiming for*, provided they're not having lots of hypos. I think WHO guidelines call for less than 6.5% (48) as the reality is once you get below this, the overall improvement in your prognosis is minimal ie. getting a reading of 5.9 doesn't dramatically improve your prospects over a 6.5% in the same way that a 6.5 does over a 7%.
*Yes, I know this is hard to do. No, I haven't personally achieved it, ever. No, I'm not criticising your control if you don't reach this point. The sad fact is, if you want to minimise the likelihood of complications, that means minimising how far you deviate from the norm. Just because something's hard to do doesn't mean it's not worth trying. The NHS considers an A1C of under 7.5 'good' and anything under 6.5 as dangerously low...and look how much it's still having to spend on treating complications. Still think they know what they're doing?