Phosphorus (P), calcium (Ca) and PTH are the main serum biochemical parameters of bone and mineral metabolism used for the current management of Chronic Kidney Disease-Mineral and Bone Disorders (CKD-MBD). This study assessed the influence of the two days (midweek, MW) or three days (post-weekend, PW) dialysis interval for blood withdrawal on serum levels of CKD-MBD biochemical parameters, their potential implications for treatment and their association with mortality.