Abstract: The present invention relates to a method for detecting at least one characteristic relating to a patient's glucose metabolism, having steps to be performed during an extracorporeal treatment of the patient's blood, particularly during a dialysis treatment, of the extracorporeal addition of glucose and/or insulin and extracorporeal measurement of a glucose concentration and/or an insulin concentration. The invention further proposes a corresponding device. In addition, the invention proposes a method for determining the composition of the dialysate for the extracorporeal treatment of a patient's blood having the steps of determining a glucose level in the patient's blood during the dialysis session and adapting the amount of glucose added to the dialysate or blood based on the glucose level determined. To this end, the invention proposes a corresponding device. The invention further proposes a blood treatment device.