The HumatroPen for injecting Human Growth Hormone is designed to provide a wide range of HGH doses and allow for precise dose adjustments for your HGH hormone shots.HumatroPen is a very easy to use injection system for hormone therapy. It is quick and easy for patients to use. Humatrope HGH must be kept refrigerated before and after it is mixed but do not freeze the cartridges. Once Humatrope has been mixed and is in liquid form, the HGH cartridges must be used within 28 days. If you are using the traditional syringe and vial method of injection, the HGH Humatrope vials must be used within 14 days. Humatrope Injections. Before giving yourself an HGH injection, check the expiration date on the Humatrope cartridge or vial and do not use the cartridge or vial if you discover it has already expired.   Hormone Shot Self-Administration. When you give yourself your HGH shot you place the head of the pen on the injection site, press down the injection button and hold it in. The Humatropen injection is finished when you have slowly counted to five while you are still holding the injection button in.Before you remove the needle from the skin make sure the HGH pen reads 0.00 in the center of the dose window.