A medication injection supervisor device, in one example embodiment, comprises a particular sleeve, the particular sleeve being designed to lock onto to a prefabricated injection pen of a particular design, a universal header designed slide onto the particular sleeve irrespective of the particular model of the prefabricated injection pen, an electronics assembly housed by the universal header, a sensor to detect an injection automatically, the sensor being communicatively coupled to the electronics assembly, a display to display injection data, and a button to allow manipulation and display of the injection data, including resetting of the time. The medication injection supervisor device can infer the completion of the injection from a plunger of the injection pen being depressed.
