The ability to confidently and consistently identify a decline in kidney function is directly linked to assessing glomerular filtration rate (GFR). This module explains the role of GFR as a reflection of kidney function, methods for measurement, and interpretation of results. It emphasizes the correlation between an increased renal biomarker and a decline in GFR. The module also covers how SDMA can provide an earlier indication of decline in GFR, creating a more robust clinical picture of a patient’s renal health.