The invention relates to the field of monitoring the hydration- and/or nutrition status of a patient by means of bioimpedance measurement values. This is based on the problem of also being able to determine by such measurements the body composition of an amputated person simply and individually. The invention is based on the observation that volume compartments can also be determined in amputated patients by means of bioimpedance measurements when reference is made to the body models, used and established hitherto for patients without amputations, without major adaptation. Merely the determining of a characteristic factor for the amputation is necessary, which can be determined by comparative measurements in advance. In particular exceptional situations of multiple amputations, it can be indicated to submit additional parameters to increase accuracy. Then the body models hitherto can also be further used for these cases.