Excretion rate of glucose increases with increasing plasma glucose concentrations- at concentrations greater than at the transport maximum (tm) for glucose, the carriers are saturated so that the reabsorption rate no longer matches the filtration rate. the difference is excreted in the urine. as the plasma glucose concentration increases, the excretion of glucose increases. when it is greater than the t m, the renal vein glucose concentration will be less than the renal artery concentration because some glucose is being excreted in urine and therefore is not returned to the blood. the clearance of glucose is zero atconcentrations lower than at tm (or lower than threshold) when all of the filtered glucose is reabsorbed, but is greater than zero at concentrations greater than tm.