Data collection apparatus for attachment to an injection device

An apparatus, comprising:

• a medicament administration apparatus comprising:
• an injection device having:
• a housing,
• a proximal end,
• a dosage knob for allowing a dosage of medicament to be set by a user, and
• a dose delivery button for allowing the user to cause delivery of medicament from the injection device;
• and
• a data collection device, wherein the data collection device is attachable to the proximal end of the injection device, wherein the data collection device:
• includes a cavity that is configured to receive the proximal end of the injection device,
• includes features that are configured to mate with one or more external features of the dosage knob of the injection device,
• is configured such that, when installed on the injection device, the data collection device is not engaged with the housing of the injection device,
• is configured such that, when installed on the injection device and , manipulated by the user, the data collection device affects operation of the injection device,
• is configured such that, when the data collection device is rotated by the user during setting of a dosage of medicament, the dosage knob also rotates,
• is configured such that movement of the data collection device in a distal direction is communicated to movement of the dose delivery button of the injection device in the distal direction,
• includes a sensor arrangement which is configured to detect rotation of the dosage knob relative to the dose delivery button when a dose is being delivered, and
• includes a processor arrangement that is configured to, based on the detected rotation of the dosage knob relative to the dose delivery button when the dose is being delivered, determine an amount of medicament amount expelled by the injection device.