The present invention concerns a double-lumen catheter and a method for delivering or withdrawing fluids to/from a patient, in particular for use in hemodialysis. The double-lumen catheter comprises an elongated tubular body having a proximal end and distal end, with the distal end being positionable within a vessel of a patient, a divider wall extending along an interior of said tubular body and separating said interior into an intake lumen and a return lumen. The intake lumen and said return lumen each comprise an opening sloping toward the divider wall and toward the distal end of the tubular body, respectively, the openings.