There is provided an auto-injector for a syringe that is suitable for use in the injected delivery of drug to a patient. The auto-injector comprises a cassette unit arranged for receipt of a syringe provided with a needle cover and removable cap. The auto-injector also comprises a drive unit arranged for docking receipt of the cassette unit at a docking position and a drive arrangement. The drive unit is provided with a timer that starts a time count on removal of the removable cap and needle cover from the cassette unit.