I had lab work done in March and my Creatinine was level was 0.70 & glomerular filtration rate (GFR) was 91. I had lab work again in June and my Creatinine was 1.9 and GFR 44. Can something cause this sudden drop? I got my Lab reports for the past 5 yrs and my numbers have always been below 1 for creatinine and above 90 for my GFR. I had a kidney stone back in February. Can my numbers go back up again?