Inulin clearance is still considered as the gold standard method to measure glomerular filtration rate. This method has been proposed in thirties by Smith and Shannon but the inulin measurement method still remains complex. Interferences, notably with the glucose, must also be considered. Two main methods have been proposed to measure inulin both in urine and plasma: "acid" or enzymatic methods. "Acid" methods are colorimetric. Fructose is actually measured after inulin hydrolysis in acid milieu. Different methods have been described to measure fructose. Among these methods, the measurement using anthrone is the most popular. Several enzymatic methods have also been published. These have more precision and the interference with glucose is probably less even if relatively few studies are available. HPLC methods for inulin measurement have also been described. This method is specific and accurate. While inulin is an unquestioned reference method for glomerular filtration rate, its measurement in urine and plasma remains tricky and at risk of interferences. Additional trials seem necessary to analytically validate and compare all the methods available on the market.