A blood sample collector can be used to collect a blood sample from a subject. The blood sample collector can be placed in a receptacle of a spectrometer to measure spectral data from the blood sample while the blood sample separates. The container may comprise a window to allow light such as infrared light to pass through the container, with the blood sample at least partially separating within the container between spectral measurements, which can provide improved accuracy of the measurements and additional information regarding the sample. The container may comprise an elongate axis and the container configured for placement in the spectrometer receptacle with the elongate axis extending toward a vertical direction in order to improve gravimetric separation of the blood sample. The spectrometer can be configured to measure the blood sample at a plurality of heights along the sample as the sample separates.