Some embodiments of the invention provide one apparatus that is suitable for both the collection and measurement of a blood sample. Once a blood sample is drawn into such an apparatus the blood sample can be analyzed, without having to transfer any portion of the blood sample into another vessel. Also, in some very specific embodiments, the apparatus is provided with an optical chamber that is specifically designed to reduce the average attenuation of electromagnetic radiation (EMR) due to scattering of EMR by the red blood cells in a blood sample, without having to hemolyze the red blood cells by using sound waves or by adding reagents to the blood sample. Moreover, as a result of the time saved by using a single apparatus for blood sample collection and measurement, the addition of an anticoagulant is not required to prevent clotting. Moreover, in such embodiments the optical chamber is designed to spread blood into a thin film, thereby reducing the incidences of trapped air bubbles in the collected blood sample in the optical chamber. Instead air bubbles are easily pushed through the optical chamber and guided out of the apparatus through a vent. Optionally, at least one biosensor may be provided within a second flow path in the apparatus.