Provided is a precision variable flow rate infusion system and method for delivering a liquid from a reservoir having an initial potential outflow rate to a patient. The system includes at least a first flexible flow rate tubing having a pre-defined flow rate selected at a maximum dosage flow rate for the liquid from the reservoir, the pre-defined flow rate being less than the initial potential outflow rate of the reservoir. Also provided is an adjustable flow rate controller having an inlet and an outlet, at least one internal fluid pathway there between and a fluid pathway modifier structured and arranged to modify the internal fluid pathway from the inlet to the outlet from a closed pathway to a maximum flow pathway with a plurality of different flow rate pathways there between. Moreover, the at least first flexible flow rate tubing and adjustable flow rate controller determine the maximum flow rate of liquid from the reservoir to a patient and the adjustable flow rate controller permits precision flow rate control from an off flow rate to about the maximum flow rate permitted. Associated methods of providing, calibrating and using the precision variable flow rate infusion system are also provided.