That's an excellent improvement. What medication are you on? Some people find that metformin disagrees with their digestion but there is a slow release version which many people tolerate better...
That is a great improvement to you HbA1C- I'm sorry it came at the expense of other symptoms. I agree with @EllieM that many seem to do better on the slow release version of Metformin- I was put on the slow release straight away so I do have to thank my doctor for that.
I am not on any diabetes med all I have done is cut out Carbs from the food I am eating so low carb/keto I feel better for doing this and have lost 8.8 kg but still have more to loose doctors said my body doesn't like meds hence the Diorhhea (sorry).