Hi CeciliaT, that is an excellent question, one frequently asked. The short answer is a long one though.
Pre-diabetics have been know to sometimes bring their A1C back down to non-diabetic numbers; my dad being one, who changed is diet and lifestyle immediately after told he was borderline.
As for those with diabetes, it is possible to bring your number down to a point where you are extremely well managed in your diabetes. However, there is no cure or way of reversing diabetes that has been clinically affirmed.
I hope this answer helps you, please reach out if you have other questions.
-Samuel, community moderator