The invention provides for a drug delivery device (130), comprising a hollow container comprising a wall structure and an internal volume (110) surrounded by the wall structure, the hollow container being adapted to contain within or transport through the internal volume a liquid drug to be supplied to a patient, the wall structure comprising an optical waveguide wall material (106), the optical waveguide wall material comprising a light scattering characteristic； and a light source (120), adapted to illuminate the internal volume by emitting illumination light such that the illumination light is coupled into the optical waveguide wall material through a light coupling area (122) of the wall structure, propagates through the optical waveguide wall material by total internal reflection and is scattered into the internal volume by the light scattering characteristic.
