My Aic Levels Have Been At 5.8 To 5.9 For

My aic levels have been at 5.8 to 5.9 for some time now. All other labs are fine. I am 69 years old and my doc decided it was best to put me on Metmorfin (500 mg twice a day). I have been on it for 2 weeks, and am nauseous most of the time, very tired, and a little lightheaded. Do I really need to be on this medicine. Can I just stop taking it - or will that have an adverse side affect. Thank you.