glomerular filtration rate (GFR) [L, glomerulus, small ball; Fr, filtre + L, ratus] , a kidney function test in which results are determined from the amount of ultrafiltrate formed by plasma flowing through the glomeruli of the kidney. The amount is calculated from inulin and creatinine clearance, serum creatinine, and blood urea nitrogen. The GFR can also be estimated from equations that include creatinine, age, gender, and ethnicity.