A sampling device for photometric determination of the content of an analyte in a sample of whole blood has at least one measuring chamber having locally transparent wall parts, at least one wall part being sufficiently deformable to facilitate displacement of the whole blood sample from the measuring chamber, with a transparent body having a radiation transmission characteristic dependent upon the concentration of a predetermined analyte in the whole blood sample disposed between the wall parts. The sampling device is employed in an analyzer for photometric determination of the content of analyte in a sample of whole blood and in a method of photometric in vitro determination of the content of an analyte in a sample of whole blood. In the method, a sample of whole blood is transferred directly from an in vivo locality to the sampling device, the measuring chamber therein is deformed in a controlled manner to substantially drain the whole blood from the measuring chamber, radiation is transmitted through the substantially drained measuring chamber, detected, and the analyte content determined. A measuring chamber for photometric determination of an analyte in a sample of whole blood has locally transparent wall parts, at least one being sufficiently deformable to facilitate displacement of the whole blood sample from the measuring chamber, and a transparent body disposed between the wall parts. The measuring chamber is employed in an analyzer and in a method for the photometric determination of an analyte in a sample of whole blood.