An apparatus for the measurement of at least one analyte in the blood of a patient, which includes a light source generating broadband light and a light-transmission arrangement having a plurality of transmitting fibers is positioned for simultaneously transmitting multiple wavelengths of the broadband light from the light source to the blood of the patient. The measurement apparatus further includes an optical fiber arrangement having a plurality of light detector fibers for leading multi-wavelength light, in spectrally unseparated form, transmitted through, or reflected from, the blood and a light detection arrangement for receiving the multi-wavelength light in its spectrally unseparated form from the optical fiber arrangement, for spectrally decomposing the received light, and for determining amplitudes of selected wavelengths of the decomposed light. The measurement apparatus utilizes a non-pulsatile element of the patient's blood for determining the measurement of at least one analyte in the blood as a function of the amplitudes of the selected wavelengths.