A method for detecting in-vivo properties of a biosensor. In the inventive method, a sensitivity-to-admittance relation is provided and a raw current in the biosensor is measured. An in-vivo current response is also measured at first and second operating points. A time constant τ is determined by the electrical capacitance C of the working electrode and the electrical resistance RM of the membrane by τ=RM·C. The first and second operating points are selected below and above τ, respectively. An analyte value in a sample of a body fluid is determined by using the raw current and compensating sensitivity drift in the biosensor, which in turn is compensated by using the measured value for the raw current and a corrected value for the sensitivity. The failsafe operation of the biosensor is monitored by using the in-vivo current response measured at the first and second operating points.
