肾功能(Renal function)、在肾脏是指肾脏状态的指示及其在肾生理作用的角色。肾小球滤过率(Glomerular filtration rate/GFR、肾丝球滤过率)描述了通过肾脏过滤流体之流速。肌酸酐清除率(Creatinine clearance rate、C_Cr 或 CrCl)是指血浆中的单位时间内肌酸酐的清除功能比率，亦是近似GFR的一个有用的量度。此外由于肌酸酐的分泌所造成的肌酸酐清除率超过GFR，而肌酸酐的分泌可被西咪替丁所阻断。另一方面，旧式的血清肌酸酐方法之过度估计导致了低估肌酸酐清除率，因而提供了GFR的较低的偏差估计值。 不过目前GFR及C_Cr已经可以精确地由在血液和尿液的物质比较测量而计算出，或则只用验血结果(检验两个参数eGFR(估计小球滤过率)及eC_Cr(估计肌酸酐清除率))的公式估算。

Renal function, in nephrology, is an indication of the state of the kidney and its role in renal physiology. Glomerular filtration rate (GFR) describes the flow rate of filtered fluid through the kidney. Creatinine clearance rate (C_Cr or CrCl) is the volume of blood plasma that is cleared of creatinine per unit time and is a useful measure for approximating the GFR. Creatinine clearance exceeds GFR due to creatinine secretion, which can be blocked by cimetidine. In alternative fashion, overestimation by older serum creatinine methods resulted in an underestimation of creatinine clearance, which provided a less biased estimate of GFR. Both GFR and C_Cr may be accurately calculated by comparative measurements of substances in the blood and urine, or estimated by formulas using just a blood test result (eGFR and eC_Cr).