A method and a mixing
system (20) for in-line mixing components of a medical fluid in a mixing
system (20), the medical fluid having a final predetermined composition of pure water, a small-
signal-response, SSR-, component and optionally at least one
electrolyte component. The method comprises: providing (S1) a flow of fluid comprising pure water, or a mixture of pure water and an
electrolyte component, in a main fluid line (21); monitoring (S2), with a concentration sensor (26, 60), a concentration of the fluid; providing (S3), with an SSR dosing mechanism (25a), the SSR-component into the flow of fluid upstream the concentration sensor (26, (60); and controlling (S4), with the SSR dosing mechanism (25a), the dosing rate of the SSR-component to an initial dosing rate at which the concentration monitored with the concentration sensor (26, 60) indicates an initial concentration (cSSR_
init) of the SSR-component in the fluid that is greater than an intended final predetermined concentration (cSSR_final) of the SSR-component in the medical fluid, in order to determine a relationship between the dosing rate of the SSR-component and the resulting concentration of the SSR-component in the fluid. The method further comprises
downscaling (S5), with the SSR dosing mechanism (25a), the dosing rate of the SSR-component to a final dosing rate (QSSR_final) at which the final predetermined concentration (cSSR_final) of the SSR-component in the fluid is achieved, based on the determined relationship.