Doctor said metformin might be working too well on me.. Huh?

Was diagnosed about 5 days ago with an a1c of 12% and been on metforming since. My glucose level went from 14.5 to 6-6.5 (i even saw 5.7 after my gym session 3 days ago).

Had to go to the doctor today because ive been feeling like crap (vomiting and feeling very weak) and doctor said that the 500 mg metformin ive been taking might be working too well for me. I completely forgot to ask him what he means as i was feeling like i was about to throw up.

What am i suppose to do with this information?