The glomerular filtration rate (GFR) is defined as the volume of fluid that is filtered by the glomeruli of the nephronsNephrone sind die Filtereinheiten der Nieren.... of both kidneys per unit of time to produce primary urineThe initial urine entering the nephron due to filtration of the blood at renal corpuscles. It is not yet concentrated and does not contain any proteins..... It is, therefore, the chief measure of kidney function. The rate corresponds to a mathematical value.