One example discloses a handheld medical device, comprising: a patient attribute sensor input configured to receive a patient attribute input signal; a dosage calculator configured to output a prescribed dosage volume output signal in response to the patient attribute input signal; a dosage volume sensor input configured to receive an actual dosage volume input signal; and a dosage comparator configured to generate a comparator output signal based on a comparison between the prescribed dosage volume output signal and the actual dosage volume input signal.