Embodiments of the present disclosure relate to approaches for more efficiently measuring glucose levels using a wearable drug delivery device. In some embodiments, the wearable drug delivery device may include a needle deployment component including a cannula and an optical conduit deployable into a user, the cannula operable to deliver a liquid drug to the user. The wearable drug delivery device may further include a glucose monitor including an optical sensor, the optical sensor operable to measure a light output received via the optical conduit.