A method of identifying a patient who is non-compliant with prescribed diet and/or phosphate binder regimen calculates a phosphorus-protein ratio (PPR) by calculating the patient's protein intake, measuring the patient's serum phosphorus concentration, and estimating the amount of phosphorus removed by the patient's kidneys from measured residual urea clearance. The PPR is the ratio between the total amount of phosphorus removed from the patient and the patient's protein intake. The method enables identifying a patient that is non-compliant with prescribed diet and/or phosphate binder regimen if the PPR is outside of an acceptable range.