Systems and methods of micro-infusion of medical fluids are disclosed. Micro-infusion systems may include a pump, a patient interface, tubing between the pump and the interface, and a micro-infusion device along the tubing. A first portion of the tubing above the micro-infusion device is longer than a second portion of the tubing below the device. The micro-infusion device may include a chamber in-line with the tubing, a first valve between the chamber and the first portion of the tubing, a second valve between the chamber and the second portion of the tubing and a third valve between the chamber and a dump chamber. The second valve may be slidably disposed within the chamber. A medical fluid may be provided into the chamber that slides the second valve displacing another fluid in the chamber through the third valve into the dump chamber.