The device for measuring and displaying the concentration of glucose in the blood comprises a display device (2) into which disposable sensors (1) comprising a biomembrane (9) can be inserted. The display device (2) comprises a built-in computer (3) in whose memory (7) a glucose concentration diagram (5) is stored and which can evaluate the measurement results of the sensors (1). The computer (3) comprises a time measuring device (4) whose zero setting can be correlated in an irreversible manner with the date of manufacture of the disposable sensors (1). Before the device is supplied to the patient, the glucose concentration diagram, which corresponds to the characteristics of the biomembrane (9) of the disposable sensors (1) at the time of manufacture, is irreversibly calibrated. The glucose concentration diagram is automatically and irreversibly corrected, taking into account the time-dependent characteristics of the biomembrane (9) of the disposable sensors (1), by means of the time measuring device (4).