Will Metformin And Onglyza Cause Adverse Effects On Kidney?

In recent months, my creatinine level has increased to 1.55 and my GFR has decreased to 34. I stopped taking NSAIDS and metformin until some testing could be done. The renal doctor stated I could go back on metformin. My family doctor recommends 500mg metformin combined with 5mg onglyza daily. With the warnings on both of these meds, I m uncertain if this is a healthy move. Meanwhile, my A1c is 7.3 and daily testing is under 200 in the morning. Will metformin and onglyza hurt my kidneys? Should I consider an injection of some type instead? My only hope is to keep good control on my diabetes.