The concentration of creatinine in serum is the most widely used and commonly accepted measure of renal function in clinical medicine. Serum urea level along with serum creatinine level are frequently used for the evaluation of renal function, since the levels of these two waste products help in the differential diagnosis of pre-renal, renal and post-renal hyperuremia. Presently there is no creatinine analyzer that can handle whole blood. The laboratory turn around time may range from 15-90 min even for a simple electrolyte analysis, which is not acceptable for treatment of acute renal failures. The applicants believe that the development of a suitable creatinine sensor that can be integrated into existing blood gas/electrolyte analyzers is a significant technological innovation with a potentially large commercial application. Their approach to this problem is to develop sensors based on enzymatic decomposition of creatinine followed by the electrochemical detection of one of the reaction products. Phase I aims include development of the sensor Membranes and tests on the key sensor parameters.