The present invention relates to a method for preparing a medical solution from at least one first liquid component and at least one second liquid component, wherein the first component and the second component are conveyed with a respective conveying means to obtain a mixed solution, wherein the conveying means are operated such that a modulation of the concentration of the first and second components takes place and the conductivity or a parameter of the mixed solution correlating with the conductivity is measured at a measurement point, wherein the modulation of the concentrations takes place in a desired state such that no modulation or a specific desired modulation of the measured conductivity or of the parameter correlated with the conductivity occurs. The present invention furthermore relates to an apparatus for preparing a medical solution as well as to a blood treatment device having such an apparatus.