A volumetric infusion pump useful in intravenous feeding includes a detector which provides an alarm when the supply bag or reservoir becomes empty or an occlusion occurs between the supply bag and the pump. The pump includes a first pumping chamber having a cylinder, a piston, a first flexible diaphragm and first and second valves. The piston is driven by a first cam through a first cam follower which is connected to the piston. The empty supply bag detector senses contact between the first cam and the first cam follower. During normal operation, when the first valve opens and the second valve closes the first pumping chamber fills due to the head pressure of fluid from the bag, and the cam follower remains in contact with the cam. When the supply bag becomes empty due to an improper setup or a system malfunction such as an occlusion occurs, head pressure in the fluid being supplied to the pumping chamber is lost, and the cam follower no longer can maintain contact with the cam during the fill portion of the pumping cycle. This results in an alarm signal which stops the pump.