A dialysis system may include a blood circuit, a cassette, a subsystem having a processor, a sensor, and a blood pumping mechanism, a housing in which the subsystem is arranged, a movable support arranged in the housing and configured to hold the sensor and/or the blood pumping mechanism of the subsystem, a cassette holder configured to removably receive the cassette, and a loading system. The loading system may be configured to move the movable support, e.g. by an axial movement, to a first position and to a second position relatively to the housing while the cassette holder is fixedly arranged in the housing. The loading system may have an electric motor controlled by the processor, a drive assembly coupled to the electric motor, and a guiding assembly configured to cooperate with the drive assembly.