Biosensor by means of which biological fluids are analysed, comprising at least the following layers: a functional layer A1 which constitutes the base layer of the biosensor, a functional layer A3 which is composed of a polymer film which has at least partially a hydrophilic coating, a double-sided pressure-sensitive adhesive tape A2 which joins the functional layers A1 and A3 to one another and in which a measuring channel is provided whose lid is formed by the functional layer A3 and whose base is formed by the functional layer A1, characterized in that the polymer film of the functional layer A3 has on its inside, which forms a wall of the measuring channel formed by the functional layer A2, at least one venting notch which is disposed above the measuring channel in such a way that the venting notch vents the measuring channel.