This application relates to a medicament delivery device such as medicament injection pen that can distinguish between a priming dosage and the injection of therapeutic dosage into a patient. In one aspect, the medicament injection device includes a housing having a chamber configured to contain a cartridge of medicament, and a dose setting and dispensing mechanism configured to set and dispense a dose of the medicament from the cartridge. The device may also include a logging module configured to detect and record as a pen event a dispensed volume of a medicament dose and a time when the medicament dose is dispensed. The device may further include a dose distinguisher configured to distinguish between pen events associated with priming doses and pen events associated with therapeutic doses based at least in part on historical user data identifying pen events as a therapeutic pen event or a priming pen event.