Method as well a kit for the performance of the method for the investigation of biological samples from a mammal for at least one component, wherein the method includes the following steps: (a) Administering at least one marker substance to a mammal； (b) Waiting for a length of time which is sufficient for the at least one marker substance to reach the location of sample removal； (c) Removing a biological sample from the mammal； (d) Investigating the biological sample for the presence and/or amount of at least one marker substance or a derivative thereof； and, if the at least one marker substance or the derivative thereof is detectable in the biological sample； (e) Investigating the biological sample for an analyte.
