The eGFR blood test results here (Australia) are not given an exact number, with the "e" in front of GFR meaning estimated. In the last two years of blood tests for PMR, my eGFR result has always been >90 (per 1.73sqm), with the reference range being >60. To protect kidneys I drink extra water and avoid vitamin C supplements and high oxalate foods, both of which can cause kidney stones.