A process comprises the phases of: activating a pusher, which exerts a push force on a plunger of a syringe containing the infusion liquid; measuring the push force by means of a load cell; comparing the push force with a maximum threshold; halting the pusher when the maximum threshold is exceeded; after a predetermined pause, restarting the pusher and emitting a consent signal indicating correct loading of the syringe if, within a certain time from the restart, the push force again exceeds the maximum threshold. The infusion device serves to inject an anticoagulant into an extracorporeal blood circuit. The control process guarantees against loss of infusion due to an incorrect initial loading of the syringe.