In a procedure for flushing a catheter, connected to an apparatus, implanted in a patient for infusing liquid medication, in particular insulin, through the catheter, the infusion channel (1) in the catheter is isolated from the patient and connected from a circuit (1,10,6,12,2) separated from the patient. Cleaning fluid is then flushed through the circuit. In a device for flushing a catheter, connected to an apparatus, implanted in a patient for infusing fluid medication, in particular insulin, through the catheter, the catheter is at least of a double-lumen type. One channel (1) is intended for the infusion of the medication through an outlet valve (4) in the catheter, and a second valve (6) is arranged in the tip of the catheter to interconnect the two channels (1,2). The second valve is openable, and the outlet valve is closable, so the catheter's two channels form a circuit, isolated from the patient, for flushing the infusion channel.