Sustanon is used to treat confirmed testosterone deficiency in males. The active substances of Sustanon are turned into testosterone by your body. Testosterone is the natural male hormone known as androgen. In men, testosterone is produced by the testicles. It is necessary for the growth, development, and function of the male sex organs and for secondary male sex characteristics. It is necessary for the growth of body hair, the development of bones and muscles, and it stimulates the production of red blood cells. It also makes men’s voices deepen. Preparations containing testosterone are used to replace testosterone in a person who has low or no natural testosterone.