A method and an arrangement for determining an overhydration parameter or a body composition parameter are disclosed. The method comprises:obtaining first bioimpedance measurement data of a patient from a first type of bio-impedance measurement (204),deriving bioimpedance calibration data from the first bioimpedance measurement data for calibrating second bioimpedance measurement data from a second type of bioimpedance measurement (205),obtaining the second bioimpedance measurement data from a second bioimpedance measurement of the patient (206), andcalibrating the second bioimpedance measurement data using the calibration data to determine the overhydration parameter or the body composition parameter of the patient (207).
