Sustanon (commonly known as Sustanon 250) is the brand name for an oil-based injectable testosterone blend. It is primarily formulated for testosterone replacement therapy (TRT) to treat clinical male hypogonadism or testosterone deficiency.

Unlike single-ester variations, Sustanon uniquely combines four distinct testosterone esters in a single dose: testosterone propionate, phenylpropionate, isocaproate, and decanoate. This multi-ester profile is designed to provide a rapid initial release of testosterone followed by a sustained release into the bloodstream over several weeks, reducing the frequency of required medical injections.

While legally prescribed for medical hormone deficiencies, Sustanon is frequently sought out or misused within athletic and bodybuilding communities for its powerful anabolic properties to increase muscle mass, strength, and physical recovery. However, its use carries significant health risks. Potential side effects include severe natural testosterone suppression, cardiovascular strain, liver dysfunction, acne, fluid retention, and mood alterations. Furthermore, because it is formulated with peanut oil, it is strictly contraindicated for anyone with a peanut allergy.