A precision variable flow rate infusion system for delivering a liquid from a reservoir having an initial potential outflow rate to a patient, the liquid having a maximum dosage flow rate, comprising: at least a first flexible flow rate tubing having a known length and internal diameter that define a pre-defined flow rate not exceeding the maximum dosage flow rate for the liquid, the known length and internal diameter being defined to provide a laminar flow of the liquid through the first flexible flow rate tubing; and an adjustable flow rate controller having an inlet and an outlet, at least one internal fluid pathway therebetween 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 therebetween providing from a maximum adjuster flow rate to a zero flow rate, wherein the adjustable flow rate controller is connected to the first flexible flow rate tubing and wherein the adjustable flow rate controller is configured to receive the liquid from the reservoir, in use; wherein, when the first flexible flow rate tubing and the adjustable flow rate controller are connected, the pre-defined flow rate and the maximum adjuster flow rate cooperatively combine to be equal to or less than the maximum dosage flow rate for the liquid from the reservoir; wherein the combination of the pre-defined flow rate and the maximum adjuster flow rate determine a maximum flow rate of liquid from the reservoir to a patient, which is equal to or less than the maximum dosage flow rate, and wherein the adjustable flow rate controller permits precision flow rate control from an off flow rate to about the maximum flow rate permitted by the combination of the pre-defined flow rate and the maximum adjuster flow rate. at least a first flexible flow rate tubing having a known length and internal diameter that define a pre-defined flow rate not exceeding the maximum dosage flow rate for the liquid, the known length and internal diameter being defined to provide a laminar flow of the liquid through the first flexible flow rate tubing; and an adjustable flow rate controller having an inlet and an outlet, at least one internal fluid pathway therebetween 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 therebetween providing from a maximum adjuster flow rate to a zero flow rate, wherein the adjustable flow rate controller is connected to the first flexible flow rate tubing and wherein the adjustable flow rate controller is configured to receive the liquid from the reservoir, in use; wherein, when the first flexible flow rate tubing and the adjustable flow rate controller are connected, the pre-defined flow rate and the maximum adjuster flow rate cooperatively combine to be equal to or less than the maximum dosage flow rate for the liquid from the reservoir; wherein the combination of the pre-defined flow rate and the maximum adjuster flow rate determine a maximum flow rate of liquid from the reservoir to a patient, which is equal to or less than the maximum dosage flow rate, and wherein the adjustable flow rate controller permits precision flow rate control from an off flow rate to about the maximum flow rate permitted by the combination of the pre-defined flow rate and the maximum adjuster flow rate.