Adapters for utilizing a syringe or pen injector with a subcutaneous injection port to deliver a therapeutic substance through the injection port and methods of using the adapters are provided. A syringe adapter has a body having a first end and a second end. The first end of the body is configured to receive and engage the end of a syringe so that the cannula of the syringe is held at a fixed position with the respect to the adapter. The second end of the adapter configured to mate with a mating portion of the injection port. When the second end of the adapter engages the mating portion of the injection port, the adapter assures that the cannula of the syringe is properly aligned with the subcutaneous injection port and assures that the cannula penetrates the injection port to the proper depth. Adapters for use with pen style delivery systems are also disclosed. Additionally, an adapter to facilitate loading a syringe with a therapeutic substance from a vial is disclosed.