The Creatinine Clearance Test measures how effectively the kidneys are clearing creatinine, a waste product produced by muscle metabolism, from the blood. The test involves collecting a 24-hour urine sample and a blood sample to calculate the clearance rate. Creatinine clearance provides an estimate of the glomerular filtration rate (GFR), which reflects kidney function. A low creatinine clearance can indicate kidney dysfunction or impaired filtration, commonly seen in conditions such as chronic kidney disease. This test helps assess kidney health, monitor kidney function over time, and evaluate the progression of kidney diseases.