A continuous Glomerular Filtration Rate (GFR) estimation system may include a Foley catheter, a continuous urine creatinine sensor, and a urine output monitor. The continuous GFR estimation system computes creatinine clearance as CrCl=(U.sub.cr.times.U.sub.vol)/(P.sub.cr.times.I.sub.mim), where U.sub.cr is urine creatinine in mg/dL, U.sub.vol is urine volume in mL, P.sub.cr is plasma (serum) creatinine in mL, and I.sub.min is time in minutes. A Foley catheter may be used to withdraw urine from the bladder. The urine may be delivered to a urine output monitor that provides the U.sub.vol value over a time I.sub.min. Attached to the catheter is the flow-through continuous urine creatinine sensor for providing the U.sub.cr value. The remaining parameter is P.sub.cr. Because serum creatinine levels do not change rapidly over time, a blood sample may be withdrawn prior to the start of the continuous GFR to obtain the P.sub.Cr value.