I guess metformin is working because when the egfr is 60 mean you have chronic kidney disease, its good that you done your egfr blood test and got to know this earlier.
Further renal labs and/or testing needs to be done, i.e. serum renal panel, 24 Hr Urine test, etc.
My Endocrinologist that I was seeing for thyroid issues put me on the Metformin- She said that i am pre-diabetic and this will help me and hopefully prolong my getting diabetes. Regardless- this is my first abnormal reading on the EGFR but my second abnormal on the Anion Gap.
The Metformin is not a "preventive" for Diabetes; it is a treatment for Diabetes, thus, you are Diabetic.
Is this your first abnormal reading? Any other renal labs or testing ordered?
I would be somewhat concerned.