A dose capturing assembly (200, 200) adapted to be releasably attached to or formed integrally with a drug delivery device, the drug delivery device comprising: - a housing, - a drug reservoir or means for receiving a drug reservoir, - drug expelling means comprising a rotatable dose setting member allowing a user to set a dose amount of drug to be expelled, - an actuation member actuatable between a first and a second state, the first state allowing a dose amount to be set, the second state allowing the drug expelling means to expel a set dose, and - an indicator with indicia adapted to display the set dose amount during dose setting, and to display the remaining dose amount to be expelled during drug expelling, the dose capturing assembly comprising: - a camera (221, 321) adapted to capture an indicia-containing image of the indicator, and - processor means (210, 310) adapted to: (a) determine the value of a captured image using a first image analysis process, the value corresponding to the set dose amount, characterized in that the processor means (210, 310) is further adapted to: (b) if the determined value belongs to a pre-defined group of values, then confirm the determined value based on a second image analysis process, wherein for a given value from the pre-defined group of values one or more partial image areas and an associated nominal content thereof are pre-defined, each nominal content being different from the value of a captured image using the first image analysis process, the second image analysis process comprising the steps of: (i) for a given value from the pre-defined group of values compare the captured content of the partial image areas with the nominal content, and (ii) if the captured content corresponds to the nominal content, then confirm the determined value based on the second image analysis process. - a housing, - a drug reservoir or means for receiving a drug reservoir, - drug expelling means comprising a rotatable dose setting member allowing a user to set a dose amount of drug to be expelled, - an actuation member actuatable between a first and a second state, the first state allowing a dose amount to be set, the second state allowing the drug expelling means to expel a set dose, and - an indicator with indicia adapted to display the set dose amount during dose setting, and to display the remaining dose amount to be expelled during drug expelling, - a camera (221, 321) adapted to capture an indicia-containing image of the indicator, and - processor means (210, 310) adapted to: (a) determine the value of a captured image using a first image analysis process, the value corresponding to the set dose amount, characterized in that the processor means (210, 310) is further adapted to: (b) if the determined value belongs to a pre-defined group of values, then confirm the determined value based on a second image analysis process, wherein for a given value from the pre-defined group of values one or more partial image areas and an associated nominal content thereof are pre-defined, each nominal content being different from the value of a captured image using the first image analysis process, the second image analysis process comprising the steps of: (i) for a given value from the pre-defined group of values compare the captured content of the partial image areas with the nominal content, and (ii) if the captured content corresponds to the nominal content, then confirm the determined value based on the second image analysis process. (a) determine the value of a captured image using a first image analysis process, the value corresponding to the set dose amount, characterized in that the processor means (210, 310) is further adapted to: (b) if the determined value belongs to a pre-defined group of values, then confirm the determined value based on a second image analysis process, (i) for a given value from the pre-defined group of values compare the captured content of the partial image areas with the nominal content, and (ii) if the captured content corresponds to the nominal content, then confirm the determined value based on the second image analysis process.