RAD 140, also called Testolone, is an experimental drug that activates androgen receptors in muscle and bone tissue while largely bypassing the prostate. It belongs to a class of compounds called selective androgen receptor modulators (SARMs), designed to mimic some effects of testosterone with fewer hormonal side effects. RAD 140 is not approved for human use by any regulatory agency, and it carries real health risks that are still being characterized.
How RAD 140 Works in the Body
RAD 140 binds to androgen receptors with high affinity and specificity. Androgen receptors are the docking sites that testosterone uses to trigger muscle growth, bone density changes, and other masculinizing effects. What makes RAD 140 different from testosterone is its selectivity: it activates these receptors in certain tissues (like skeletal muscle) but not in others (like the prostate). In lab studies, RAD 140 activated androgen receptors in breast cancer cells but not in prostate cancer cells, demonstrating this tissue-specific behavior.
This selectivity is the entire appeal of SARMs. In theory, you get the muscle-building signal without the prostate enlargement, hair loss, or other androgenic side effects that come with anabolic steroids. In practice, the selectivity isn’t perfect, and the compound still disrupts your hormonal system in significant ways.
The drug has a half-life of roughly 45 hours, meaning it stays active in your system for nearly two days after a single dose. This long duration supports once-daily dosing in the clinical trials that have been conducted.
Effects on Muscle and Strength
The primary reason people seek out RAD 140 is for building muscle. Users commonly report gaining 5 to 10 pounds of lean muscle mass over a cycle of 6 to 8 weeks, with relatively little water retention compared to traditional anabolic steroids. Strength increases of 20 to 30 percent on major lifts like the squat, bench press, and deadlift are frequently reported during that same timeframe.
These figures come from user reports and case studies rather than large controlled trials. One frequently cited example involves a bodybuilder who gained 8 pounds of lean muscle in 6 weeks, and an athlete who increased squat strength by 25 percent after just 4 weeks. Individual results vary significantly depending on training intensity, diet, genetics, and dosage. Still, the anabolic effect is real and consistent enough that RAD 140 has become one of the most popular SARMs in bodybuilding communities.
Potential Neuroprotective Effects
Lab research has found that RAD 140 may protect brain cells from damage caused by amyloid-beta, the protein that accumulates in the brains of people with Alzheimer’s disease. In cell cultures, exposure to amyloid-beta killed roughly half of the neurons. Pretreating those neurons with RAD 140 significantly improved survival, with the protective effect increasing at higher concentrations. The minimum effective dose in this experiment was quite low (30 nanomolar).
This is purely preclinical data from cells in a dish, not from human brains. No one should take RAD 140 expecting cognitive protection. But it does suggest the compound interacts with androgen receptors in neural tissue in potentially meaningful ways.
Liver Damage Risk
The most alarming documented risk of RAD 140 is liver toxicity. A case published in The American Journal of Gastroenterology describes a 29-year-old man with no prior health problems who developed severe jaundice and lethargy after taking RAD 140 for a few months. His bilirubin level, a marker of liver dysfunction, was nearly seven times the upper limit of normal at initial presentation and continued climbing to 42 mg/dL before slowly improving.
He was diagnosed with drug-induced liver injury caused by RAD 140. The authors noted that recovery can take 3 to 5 months for liver values to return to normal, and that acute liver failure requiring transplant remains a real possibility with this type of injury. This isn’t an isolated report. The pattern of liver enzyme elevation has appeared repeatedly in SARM users, with one documented case showing ALT (a liver enzyme) tripling from 20 to 61 IU/L after just 5 weeks of use.
Cholesterol and Cardiovascular Effects
RAD 140 significantly lowers HDL cholesterol, the type that protects against heart disease. In one case, HDL dropped from 55 to 35 mg/dL after 5 weeks of SARM use. That’s a 36 percent reduction, moving from a healthy level to one associated with increased cardiovascular risk. A systematic review of SARM clinical trials found that dose-dependent reductions in HDL were one of the most consistent adverse effects across multiple compounds in the class.
The good news from the available data is that HDL levels appear to recover. In at least one study, cholesterol returned to baseline about 25 days after the last dose. But during a cycle, your cardiovascular risk profile worsens meaningfully, and the long-term consequences of repeated cycles are unknown. The FDA has specifically warned that SARMs may increase the risk of heart attack and stroke.
Hormonal Suppression
Like anabolic steroids, RAD 140 suppresses your body’s natural testosterone production. When your androgen receptors are being activated by an external compound, the feedback loop that controls testosterone output registers the signal and dials down production. Users typically experience lowered testosterone levels during and after a cycle, which can cause fatigue, reduced libido, mood changes, and loss of the muscle gained during the cycle. This is why many SARM users follow their cycles with post-cycle therapy to help restart natural hormone production.
The Only Completed Human Trial
RAD 140 has been through exactly one completed human clinical trial: a Phase 1 study in postmenopausal women with hormone receptor-positive breast cancer, finished in September 2020. The study tested doses of 50 to 100 mg per day and found an acceptable safety profile at those doses, with the maximum tolerated dose set at 100 mg daily. One patient with a specific gene mutation at baseline had a partial tumor response.
This trial was designed to establish basic safety and dosing, not to measure muscle-building effects. It involved cancer patients, not healthy adults. The doses tested (50 to 100 mg) are considerably higher than what recreational users typically take, which makes direct comparisons difficult. No further clinical development for any indication has produced approved results.
Legal and Regulatory Status
RAD 140 occupies a gray area that confuses many people. It is not approved by the FDA for any medical use. It cannot be legally prescribed by a doctor. It is not a legal ingredient in dietary supplements, despite being sold online in products marketed as supplements. The FDA has issued warnings about the life-threatening risks of SARMs sold in this way.
For athletes, the picture is clearer. The World Anti-Doping Agency (WADA) prohibits all SARMs at all times, both in and out of competition, at every level from recreational to elite. RAD 140 is specifically named on the prohibited list under “Other Anabolic Agents.” USADA, the U.S. anti-doping agency, has emphasized that this ban applies even to recreational-level competitors.
RAD 140 is currently sold as a “research chemical,” which is the loophole that allows it to exist on the market. Sellers label it “not for human consumption,” but the products are clearly marketed to bodybuilders and fitness enthusiasts. The quality, purity, and actual contents of these products are unregulated and unverified.