Method for performing a filling and recirculation process of a blood-side conducting system of a dialysis machine using a filling device which has the following components: - a spike which is adapted for connecting the single fluid connector of a medical fluid container of the fluid system and - a manually operable fluid blocking mechanism which is arranged directly downstream of the spike and is adapted to remain fluidically connected with the spike while the filling device is in operation, whereby - the fluid blocking mechanism has at least one fluid outlet connector in the form of a second conduit which is adapted so that an arterial line section of a blood-side conducting system, can be connected to it in a detachable manner while the filling device is in operation - the fluid blocking mechanism is a 3-way switch, preferably a 3-way valve, which is arranged directly downstream of the spike, characterized by the steps: a. Connecting of the spike to the single fluid connector of the medical fluid container with the 3-way switch completely closed, and connecting of the arterial line section to the second conduit of the still closed 3-way switch with the venous fluid line section open to the environment, b. Flushing of a fluid flow path along the arterial fluid line section and the venous fluid line section by fluidically connecting the spike with the second conduit of the 3-way switch, c. Complete closing of the 3-way switch and connecting of the venous fluid line section to a third conduit of the 3-way switch, d. Recirculating of the filled-in fluid in the fluid flow path by short-circuiting the second and third conduits (14b, 14c) on the 3-way switch with simultaneous closing of the spike, e. Complete closing of the 3-way switch and uncoupling of the venous fluid line section from the third conduit and repeated flushing according to step b. and f. Complete closing of the 3-way switch in preparation for the subsequent connecting of the filled arterial and venous fluid line sections (2, 4) to a patient. - a spike which is adapted for connecting the single fluid connector of a medical fluid container of the fluid system and - a manually operable fluid blocking mechanism which is arranged directly downstream of the spike and is adapted to remain fluidically connected with the spike while the filling device is in operation, whereby - the fluid blocking mechanism has at least one fluid outlet connector in the form of a second conduit which is adapted so that an arterial line section of a blood-side conducting system, can be connected to it in a detachable manner while the filling device is in operation - the fluid blocking mechanism is a 3-way switch, preferably a 3-way valve, which is arranged directly downstream of the spike, characterized by the steps: a. Connecting of the spike to the single fluid connector of the medical fluid container with the 3-way switch completely closed, and connecting of the arterial line section to the second conduit of the still closed 3-way switch with the venous fluid line section open to the environment, b. Flushing of a fluid flow path along the arterial fluid line section and the venous fluid line section by fluidically connecting the spike with the second conduit of the 3-way switch, c. Complete closing of the 3-way switch and connecting of the venous fluid line section to a third conduit of the 3-way switch, d. Recirculating of the filled-in fluid in the fluid flow path by short-circuiting the second and third conduits (14b, 14c) on the 3-way switch with simultaneous closing of the spike, e. Complete closing of the 3-way switch and uncoupling of the venous fluid line section from the third conduit and repeated flushing according to step b. and f. Complete closing of the 3-way switch in preparation for the subsequent connecting of the filled arterial and venous fluid line sections (2, 4) to a patient. a. Connecting of the spike to the single fluid connector of the medical fluid container with the 3-way switch completely closed, and connecting of the arterial line section to the second conduit of the still closed 3-way switch with the venous fluid line section open to the environment, b. Flushing of a fluid flow path along the arterial fluid line section and the venous fluid line section by fluidically connecting the spike with the second conduit of the 3-way switch, c. Complete closing of the 3-way switch and connecting of the venous fluid line section to a third conduit of the 3-way switch, d. Recirculating of the filled-in fluid in the fluid flow path by short-circuiting the second and third conduits (14b, 14c) on the 3-way switch with simultaneous closing of the spike, e. Complete closing of the 3-way switch and uncoupling of the venous fluid line section from the third conduit and repeated flushing according to step b. and f. Complete closing of the 3-way switch in preparation for the subsequent connecting of the filled arterial and venous fluid line sections (2, 4) to a patient.