Blast injury to the external genitalia is associated with considerable morbidity, including the risk of primary hypogonadism due to insufficient testosterone. It is of the utmost importance that, prior to any testosterone replacement being commenced, serious consideration is given to sperm retrieval. The clinical and biochemical picture of hypogonadism allows a relatively straightforward diagnosis in most cases although it is important to be alert to the possibility of hypogonadism in the context of partial testicular tissue preservation. It is also prudent to consider the possibility of secondary hypogonadism especially in patients with chronic pain or those on opiate medication. Therapeutic options for testosterone replacement are diverse but relatively simple. This article aims to give guidance to the non-specialist in the consideration, diagnosis, and treatment of hypogonadism, with particular reference to blast injury of the external genitalia.