A sensor adapted for sensing of glucose, urea or lactate, the sensor configured to be implanted in the body of a living creature or an object and configured for sensing in tissue or bodily fluids, the sensor comprising - a radiation source configured for irradiating said tissue or bodily fluids in a measurement region, an integrated radiation processor and an integrated detection element, whereby integrated refers to monolithical integration using a single processing flow, heterogeneous integration for which components are processed in separate process flows but which are integrated at die or wafer level or hybrid integration of components or materials on processed photonic integrated platforms, the sensor furthermore comprising the measurement region from which the radiation interacting with the glucose, urea or lactate is captured, characterised in that - the integrated radiation processor is integrated in a silicon photonics integrated circuit and configured for spectrally processing radiation interacting with the glucose or urea or lactate, wherein the radiation processor comprises at least an integrated optical waveguide, a multiplexer and/or de-multiplexer adapted for obtaining spectrally resolved information from the spectrally processed radiation, and - the integrated detection element is integrated in said silicon photonics integrated circuit and being configured for detecting the radiation processed by the radiation processor, the radiation processor and the detection element forming an integrated spectrometer in said silicon photonics circuit and being configured for performing spectral absorption measurements for detecting spectral absorption bands of glucose, urea or lactate for performing a quantification of glucose, urea or lactate based thereon, and the radiation processor and the measurement region being configured for allowing substance-sampling free spectral absorption measurements so that sensing can be performed without the need for extracting a sample or guiding a substance of interest in a forced manner to the measurement region. - a radiation source configured for irradiating said tissue or bodily fluids in a measurement region, an integrated radiation processor and an integrated detection element, whereby integrated refers to monolithical integration using a single processing flow, heterogeneous integration for which components are processed in separate process flows but which are integrated at die or wafer level or hybrid integration of components or materials on processed photonic integrated platforms, the sensor furthermore comprising the measurement region from which the radiation interacting with the glucose, urea or lactate is captured, characterised in that - the integrated radiation processor is integrated in a silicon photonics integrated circuit and configured for spectrally processing radiation interacting with the glucose or urea or lactate, wherein the radiation processor comprises at least an integrated optical waveguide, a multiplexer and/or de-multiplexer adapted for obtaining spectrally resolved information from the spectrally processed radiation, and - the integrated detection element is integrated in said silicon photonics integrated circuit and being configured for detecting the radiation processed by the radiation processor, the radiation processor and the detection element forming an integrated spectrometer in said silicon photonics circuit and being configured for performing spectral absorption measurements for detecting spectral absorption bands of glucose, urea or lactate for performing a quantification of glucose, urea or lactate based thereon, and the radiation processor and the measurement region being configured for allowing substance-sampling free spectral absorption measurements so that sensing can be performed without the need for extracting a sample or guiding a substance of interest in a forced manner to the measurement region.