The present invention relates to a dose indicating mechanism for a drug delivery device for displaying of a dose of a medicament to be dispensed by the drug delivery device, the dose indicating mechanism comprising: an elongated housing (212) extending in an axial direction (1, 2) and having at least a first window (225) and a second window (235) that are spaced apart from each other in axial direction (1, 2), a dose indicating sleeve (200) movably disposed in the housing (212) and having at least one dose indication (204) coinciding with the first window (225) to display the size of a dose actually set, an indicator (206) operably engaged with the dose indicating sleeve (200) and axially displaceable relative to the housing (212) to coincide with the second window (235) for indicating an operational status of the dose indicating mechanism.