Testosterone (esters)
Also known as: enanthate, cypionate, propionate, undecanoate, test
The natural male androgen; injected esters are the reference anabolic steroid all others are measured against.
Legal status: UK: Class C controlled drug and prescription-only medicine. Supplying it (including to friends) and importing it by post are criminal offences; personal possession for your own use generally is not. Checked 2026-07-26.
Prohibited in sport: Yes — on the WADA Prohibited List.
Approved medical use: Licensed for testosterone-replacement therapy in men with clinically diagnosed hypogonadism.
What it is
Testosterone is the body's principal male sex hormone. As a drug it is given as an ester (a fatty-acid tail slows release) and is the compound every other anabolic steroid is designed to imitate. In medicine it treats diagnosed hypogonadism; in a performance context it is used at supraphysiological levels far above what the body makes.
Testosterone-replacement therapy is a legitimate, doctor-supervised treatment for men whose bodies do not produce enough — a different thing, at different levels, from performance use.
What’s claimed
- Increased muscle mass and strength
- Faster recovery between sessions
- Improved confidence and drive
What the evidence shows
That testosterone above natural levels increases muscle size and strength is one of the few genuinely well-supported claims in this whole area (Gold): controlled trials show a clear dose-response. What the same evidence base shows just as clearly is that those gains come with real physiological cost, and that the effect on actual athletic performance is far less clean than the effect on the scale.
The risks
- Cardiovascular: raised haematocrit (thicker blood), adverse cholesterol shifts, left-ventricular changes and higher long-term cardiovascular risk with sustained supraphysiological use.
- Endocrine: shutdown of the body's own testosterone production (HPTA suppression), testicular atrophy and impaired fertility — sometimes slow or incomplete to recover.
- Oestrogenic: gynaecomastia and fluid retention as testosterone aromatises to oestrogen.
- Psychiatric: irritability, aggression and mood disturbance in some users.
What needs monitoring
- Full blood count (haematocrit/haemoglobin)
- Lipid profile
- Blood pressure
- Liver and kidney markers
- Cardiac review where use is sustained — a doctor is the right person to arrange and read these.
Sources
- NHS. Anabolic steroid misuse — health risks and the law.
- GOV.UK. Controlled drugs: Misuse of Drugs Act 1971 drug classes.
- World Anti-Doping Agency. The Prohibited List.
- Pope HG, et al. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocr Rev. 2014;35(3):341-375.