Testosterone enanthate is a synthetic form of the naturally occurring hormone testosterone. It is an androgen and anabolic steroid that is commonly used for testosterone replacement therapy in males with hypogonadism (low testosterone levels). It is also sometimes used off-label for other purposes, such as building muscle mass and improving athletic performance, although this use is controversial and carries potential risks. Testosterone enanthate is a long-acting ester of testosterone, meaning it is designed to be slowly released into the bloodstream over several days or weeks after injection. This allows for less frequent dosing compared to shorter-acting testosterone formulations. The drug is typically administered by deep intramuscular injection every one to four weeks, with dosage and frequency determined by factors such as the individual's age, body weight, and the severity of their hypogonadism or other condition being treated. Like other forms of testosterone therapy, potential side effects of testosterone enanthate can include acne, sleep apnea, male pattern baldness, and potential cardiovascular risks. It may also cause or worsen prostate issues and increase the risk of developing male breast cancer. Regular monitoring of prostate health and red blood cell levels is recommended during treatment. Testosterone enanthate should be used with caution in individuals with certain medical conditions, such as heart disease, liver or kidney disease, sleep apnea, or breast or prostate cancer. It is also contraindicated in women who are pregnant or breastfeeding. It is important to follow dosage instructions carefully and only use testosterone enanthate under medical supervision, as misuse or abuse can lead to serious health consequences.