Needle for penetrating a membrane

A membrane penetrating needle for repeatedly penetrating a membrane, having a pointed end provided with a blunt penetrating tip and with an opening for letting a liquid in and/or out in a main direction which is substantially parallel to the longitudinal extension of the needle, wherein the blunt penetrating tip is designed with a rounded point to initially prick a membrane when the membrane is penetrated and that the outer edges present on the pointed end in the area from the rounded point to a position beyond the opening are rounded so that after the initial penetration the pointed end will push the membrane material away rather than cutting the membrane material;

• wherein the rounded point is arranged to lie substantially on a longitudinal centre line of the needle when viewed along the longitudinal centre line of the needle, and wherein the cross section of the penetrating tip of said membrane penetrating needle is substantially triangular with rounded corners and has a symmetry causing at least three substantially equally sized forces (F) in different directions which are radial to the longitudinal centre line of the needle and which forces counteract each other so that the needle will tend not to deviate from the initial penetration direction when the needle penetrates a membrane.