Always difficult answering these where we may disagree with a doctor! The original HbA1c test result was NOT a pre-diabetic result based on all the guidance on these matters, it's a diabetic result. However, you're now obviously doing things to improve your blood sugar levels, presumably diet and exercise, and getting great results so well done. Personally, I'd resist the Metformin and try to improve even further on your already good results by carrying on the good work you're doing. I was about the same as you with my first test, I'm not on medication, and I've got down to below 6 now. But your doctor knows your specific circumstances so we can't just say "don't take the meds", I can only say what I'd do.
Malc