A hemodialysis machine comprising a fluid pathway for delivering a dialysate solution, wherein the fluid pathway comprises a pre-dialysis pathway and a post-dialysis pathway, a dialyser for dialysing patient's blood using the dialysate solution, the dialyser connected between the pre-dialysis pathway and the post-dialysis pathway, a first sensor system configured to sense a characteristic of the dialysate solution at a first location on the pre-dialysis pathway, a second sensor system configured to sense a characteristic of the dialysate solution at a second location on the post-dialysis pathway, and a control system configured to make a comparative analysis of the measurements taken by the first sensor and the second sensor for monitoring the composition of the dialysate solution.
