A disposable single-needle extracorporeal blood treatment circuit for such treatments of blood hemofiltration, plasma filtration, detoxification and alike includes a manually operated syringe attached to a proximal bifurcation and a patient's access port attached to a distal bifurcation. Both bifurcations are connected with each other by a withdrawal line and in parallel by a treatment loop including a blood treatment unit and an air removal element. In the first embodiment, one or two three-way valves (such as stop-cocks) are positioned at these bifurcations to allow directing the flow of blood from the patient to the syringe through the withdrawal line and redirecting the flow through the treatment loop when blood is being returned to the patient from the syringe. In a second embodiment, two check valves are positioned along said withdrawal line and said treatment loop to automatically direct the blood floe in the same manner. Additional flush and drain circuits are optionally included allowing a “stand-by” mode of operation.