HCG injection is a medication that contains human chorionic gonadotropin (HCG), a hormone that is naturally produced by the placenta during pregnancy. It is primarily used to treat fertility issues in women and men, as well as to help with weight loss and certain medical conditions. In women, HCG injection is used to stimulate ovulation and increase the chances of pregnancy. It is typically administered as an injection in combination with other fertility medications. In men, HCG injection is used to increase testosterone production and improve fertility. It can also be used to treat medical conditions such as cryptorchidism (undescended testes) and hypogonadism (low testosterone levels).