A battery-powered device intended to be used with an insulin autoinjector (insulin pen) to provide the patient with an indication of time elapsed since last insulin injection to help manage self-administration of insulin injections. It is in the form of a pen cap with an integrated timer that typically starts timing when placed on the pen and resets soon after being removed. It is intended to replace the pen’s original protective cap and is normally available [non-prescription] over-the-counter (OTC). This is a reusable device.