“Gear” is slang for injectable testosterone and other anabolic steroids used for muscle building outside of a medical prescription. The term comes from bodybuilding and gym culture, where it functions as a catch-all for performance-enhancing drugs, though testosterone itself is the foundation of nearly every gear cycle. Understanding what gear actually involves means looking at what’s being injected, what it does inside the body, and what it costs in terms of health.
What Gear Actually Is
At its core, gear refers to synthetic testosterone, the same hormone your body produces naturally but manufactured in a lab and delivered by injection in much higher amounts. The most common forms are testosterone cypionate, testosterone enanthate, and testosterone propionate. These are all the same base hormone attached to different chemical chains that control how quickly your body absorbs and processes the drug.
Testosterone propionate has a half-life of roughly 19 hours and needs to be injected every two to three days. Cypionate and enanthate last longer in the body and are typically injected once or twice per week. These longer-acting versions are the most popular in both medical settings and underground use because the injection schedule is more manageable.
The critical difference between gear and prescribed testosterone replacement therapy is dose. Therapeutic doses aim to bring someone’s testosterone into the normal range. Gear doses for performance enhancement run far higher. Surveys of steroid users in bodybuilding and weightlifting have documented weekly doses ranging from 250 to 3,200 milligrams, which can be 5 to 29 times greater than a standard medical dose. At those levels, testosterone stops being hormone replacement and becomes a powerful anabolic drug.
How It Builds Muscle
Testosterone is the primary male sex hormone, and one of its core jobs is signaling muscle tissue to grow. When you flood the body with doses many times above normal, this signaling gets amplified dramatically. Research published in the British Journal of Pharmacology found that a single 200-milligram injection of testosterone enanthate doubled the rate of protein synthesis in muscle tissue, while protein breakdown stayed the same. That means the body is building new muscle protein far faster than it’s losing it.
At sustained high doses, the effect goes deeper than just speeding up protein production. Testosterone activates satellite cells, which are essentially repair cells sitting on the surface of muscle fibers. These satellite cells donate new nuclei to muscle fibers, giving them a greater capacity to produce protein and grow larger. This is why steroid users can push past the size limits that natural trainees eventually hit. The muscle fibers literally gain more cellular machinery for growth. Testosterone also reduces body fat, creating the combination of rapid muscle gain and fat loss that makes gear appealing to bodybuilders.
What Users Take Alongside It
Gear cycles rarely involve testosterone alone. Because the body converts a portion of testosterone into estrogen through a process called aromatization, high doses can cause estrogen-related side effects like breast tissue growth in men (gynecomastia) and water retention. To counter this, many users take aromatase inhibitors, drugs that block the conversion of testosterone to estrogen. These keep estrogen levels low throughout a cycle.
Users also commonly plan for what happens after they stop injecting. When you supply testosterone from outside the body, your brain detects the surplus and shuts down its own production signal. The longer and heavier the cycle, the more suppressed natural production becomes. Post-cycle therapy, or PCT, is a protocol users follow to restart their own hormone production. It typically combines drugs that stimulate the testes directly with drugs that block estrogen’s suppressive effect on the brain’s hormonal signaling. A survey of 470 male steroid users found that those who used PCT reported fewer withdrawal symptoms than those who stopped without it.
Health Risks at High Doses
The most immediate and well-documented risk of supraphysiological testosterone is a condition called erythrocytosis, an abnormal increase in red blood cells. Testosterone stimulates red blood cell production both directly and by increasing iron availability in the blood. At gear-level doses, red blood cell counts can climb well above safe thresholds. This thickens the blood, which raises the risk of blood clots, heart attack, and stroke. Symptoms of thickened blood include chest pain, headaches, blurred vision, fatigue, and tingling in the extremities. Data from the Framingham Heart Study, which followed participants for 34 years, found a clear association between elevated red blood cell concentration and cardiovascular death.
The FDA has issued warnings about the risk of venous blood clots, heart attack, and stroke in patients using testosterone products, and those warnings are based on therapeutic doses. At the levels gear users take, these risks are magnified. Research also shows that supraphysiological testosterone activates inflammatory pathways in blood vessels, directly contributing to vascular dysfunction independent of blood thickness.
Other common side effects include severe cystic acne, hair loss in those genetically predisposed, liver strain (particularly with oral steroids stacked alongside injectable testosterone), elevated blood pressure, and unfavorable shifts in cholesterol where protective HDL drops and harmful LDL rises. Prolonged use can also cause testicular atrophy, since the testes shrink when they stop producing testosterone on their own. Fertility can be significantly impaired, sometimes for months or longer after stopping.
Legal Status in the United States
Testosterone is classified as a Schedule III controlled substance under the Anabolic Steroids Control Act. This means it is legal to possess and use with a valid prescription, but purchasing, possessing, or distributing it without one is a federal offense. Schedule III carries penalties that can include fines and imprisonment, and individual states may impose additional consequences. The distinction between legal testosterone replacement therapy and illegal gear use comes down entirely to whether a licensed physician prescribed it for a documented medical condition.
Why the Term “Gear” Exists
The slang serves a practical purpose. Talking openly about illegal steroid use invites legal and social scrutiny, so gym culture developed a vocabulary of euphemisms. “Gear,” “juice,” “sauce,” and “pinning” (for injecting) let users discuss cycles, sources, and protocols in semi-coded language. If someone in a gym context asks whether another person is “on gear,” they’re asking whether that person uses anabolic steroids. If someone says they’re “running gear,” they’re in the middle of a cycle. The term is almost always understood to mean injectable steroids, with testosterone as the base compound.