The GFR is the filtrate volume of all glomeruli per time unit, is 125 ml/min. or 180 l/day.
The GFR depends on the total blood flow of the kidney. A high constancy of blood circulation through an autoregulation system is ensured by changes in mean blood pressure between 85 - 190 mm Hg.
It is determined diagnostically by the clearance of unrestrictedly filtered, non-reabsorbable substances in the glomerulus (e.g. inulin or creatinine).
Chronic kidney disease and GFR:
In chronic kidney disease (CKD), five stages are distinguished on the basis of GFR:
(ml/min/1.73 m2)wikipedia.org/wiki/Glomeruläre_Filtrationsrate GFR bei Wikipedia] (Wikipedia CC-by-sa-3.0)