Supplemental Device for Attachment to an Injection Device

A supplemental device for releasable attachment to an injection device, the supplemental device comprising:

• a housing;
• an electromechanical switch arrangement having an open state and a closed state, the electromechanical switch arrangement comprising a protrusion configured to contact a surface of the injection device while the supplemental device is attached to the injection device;
• a dose dialled detector operable to detect a dose of medicament dialled into the attached injection device;
• and
• a processor arrangement configured to:
• monitor the detected dose of medicament dialled into the attached injection device;
• detect a change in the state of the electromechanical switch arrangement;
• and
• change a display output of the supplemental device when a change in the state of the electromechanical switch arrangement is detected while a zero dose is dialled into the attached injection device;
• wherein the processor is configured to change the display output of the supplemental device by cycling through menu options.