The invention relates to a dialysis machine with the capability of determining a pre-dialysis property in the blood of a dialysis patient, which dialysis machine comprises an extracorporeal blood circuit, a dialysate circuit, a dialyzer and a computing unit, wherein at least one sensor for determining a property of the dialysate is arranged in the dialysate circuit. The computing unit is configured in such a way that, during an initial phase of the dialysis treatment, temporal evaluation ranges are established in which all stability criteria from a predetermined group are satisfied, and in such a way that measurement values determined by the at least one sensor are used to determine a pre-dialysis property of the patient's blood only within these temporal evaluation ranges.
