Indwelling needle for subcutaneous administration

A method comprising:

• puncturing subcutaneous tissue of a living body with an inner needle, the inner needle including an inner needle main body possessing a distal end at which is located a sharp needle tip, the inner needle main body possessing a proximal end opposite the distal end of the inner needle main body, the inner needle also including an inner needle hub connected to the proximal end of the inner needle main body, the inner needle main body passing through a lumen in an outer needle main body of an outer needle, the outer needle main body possessing a proximal end connected to an outer needle hub, the outer needle hub including a hub insertion portion in which is positioned a distal portion of the inner needle hub;
• the puncturing of the subcutaneous tissue of the living body including puncturing the subcutaneous tissue of the living body with the sharp needle tip while a distal end of the sharp needle tip is positioned distal of the distal end of the outer needle by a distance of 2.5 mm to 9 mm;
• removing the inner needle from the outer needle after puncturing the subcutaneous tissue of the living body with the sharp needle tip, the removing of the inner needle from the outer needle occurring while outer needle remains in the living body;
• and
• delivering medicinal solution to the living body by way of the outer needle that remains in the living body.