An injection aid for a syringe includes a disk with a central orifice and a flange. The flange is located on the top of the disk, and surrounds the central orifice. The outlet end or needle hub of a syringe or insulin pen fits in the flange, with the syringe needle extending through the orifice, thereby securing the disk to the syringe. The bottom surface of the disk is generally flat. The bottom surface of the disk makes contact with the skin when the needle is inserted to the proper depth. In other words, the needle lies perpendicular to the disk and is arranged to project past the disks flat bottom surface by a set, pre-determined length. When the disk is pressed flat against a patients skin, the needle is at the proper depth for the substance being injected.