An oximeter for spectro-photometric in-vitro determination of hemoglobin derivatives in a sample, typically a hemolyzed blood sample, is provided comprising a single measurement light source emitting measurement radiation, a sample chamber, for instance a measurement cuvette containing the sample, a detector device, which records a spectrum of the measurement radiation after its interaction with the sample, and an evaluation unit following the detector device, which determines the hemoglobin derivatives and at least one further analyte from the spectrum recorded by the detector device. The measurement light source is a polychromatic LED, which for determination of hemoglobin derivatives emits measurement radiation in at least one spectral region B, in which the hemoglobin derivatives exhibit significant absorbance, and which for determination of the at least one further analyte emits measurement radiation in at least one other spectral region A, in which the at least one further analyte exhibits significant absorbance.