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RAD-140

Also sold as testolone, RAD140. Selective androgen receptor modulator (SARM).

Serious risk (4 of 5)

RAD-140 is the most potent SARM in common circulation and the one with the least human evidence behind it — it was developed for breast cancer, never tested in anyone for building muscle, and its developer moved on.

What it is

RAD-140, sold as testolone, is a selective androgen receptor modulator developed by Radius Health. Like ostarine, it was designed to activate the androgen receptor in muscle and bone while sparing other tissues.

Two facts about its history matter more than the pharmacology.

It was developed for breast cancer, not for muscle. The published work on RAD-140 in humans is oncology work — the interest was in a compound that could act on androgen-receptor-positive breast cancer with a different mechanism from existing drugs. There has never been a trial testing whether RAD-140 safely builds muscle in healthy people, because nobody ever intended to use it that way.

Radius Health did not take it forward. The programme did not lead to an approved product, and the company’s development attention went elsewhere. As with cardarine, a company walking away from its own compound is a data point, though a much less specific one — programmes end for many reasons and we do not know precisely why this one did. We are flagging that uncertainty rather than filling it in with an implication.

The practical position: RAD-140 is the most potent SARM in general circulation and the one with the thinnest human evidence base. Those two facts together are why it sits a band above ostarine.

What it actually does

RAD-140 activates the androgen receptor, with high potency and high selectivity for muscle and bone tissue over prostate.

People take it because it is strong. In the informal hierarchy that circulates among users, RAD-140 sits at the top of the SARM list — closer to a steroid in effect than ostarine is. Users report significant strength gains and rapid changes in body composition, along with aggression and a stimulant-like drive that ostarine does not produce.

We have no trial data to check any of that against. What we can say from the pharmacology is that a more potent androgen receptor agonist will do more of everything an androgen receptor agonist does — including the parts nobody wants.

What the evidence actually shows

This section is short, and its shortness is the finding.

Human trials for building muscle: none. Not “small ones”, not “early ones”. None. The systematic review of randomised SARM trials that exists covers other compounds; RAD-140 does not have the trial evidence that ostarine has.

Human work in oncology: RAD-140 was studied in the context of androgen-receptor-positive breast cancer. Those investigations were in patients with cancer, at the amounts and durations relevant to that disease, and they tell you nothing useful about a healthy twenty-five-year-old taking it to add muscle.

Preclinical work: the compound is well characterised in cells and animals. It inhibits growth in breast cancer models, and separate work found it neuroprotective in cultured neurons and in rats. That is legitimate science and it is not human safety data. Animal and cell-culture results are the beginning of a drug programme, not a substitute for one.

On suppression: there is no ambiguity about the direction, only about the magnitude. A potent androgen receptor agonist suppresses your own testosterone production. Users consistently report suppression more pronounced and slower to recover than with ostarine, which is what the pharmacology predicts. Nobody has measured it properly in a trial.

On liver injury: there is a published case of severe idiosyncratic drug-induced liver injury attributed to RAD-140 in a young man, and it sits within a broader set of SARM liver-injury reports. “Idiosyncratic” is the important word: it means it was not predictable from how much he took or how long he took it. It happened to him and not to others taking the same thing.

What that adds up to: for the use people actually put it to, RAD-140 has no human safety data at all. The confident claims you will read about it — recovery times, comparisons, what to expect — are extrapolation from user reports. They may well be roughly right. They are not evidence, and it is worth knowing which one you are relying on.

The risk profile

Serious risk (4 of 5) — Documented harm in humans that is severe, common, or hard to see coming.

What going wrong looks like from the inside

The characteristic failure with RAD-140 is that it works well enough to keep you going while the two things that matter are happening silently.

The suppression compounds, and the feedback misleads you. While you are on it you feel strong — better than on ostarine, which is the reason people move to it. The receptor is being occupied, so you do not feel your own production shutting down. What arrives after stopping is heavier than people expect: profound fatigue, flat mood, no libido, training that stops producing anything. Because RAD-140 is more potent, recovery is generally described as taking longer, and there is a well-worn trap in which someone feeling that way starts another cycle to fix it. That is the mechanism by which a few months of use becomes a couple of years of it.

The aggression and drive people report is worth naming as a warning sign rather than a benefit. If people around you have started remarking on your temper, that is a real effect of a potent androgen and it is information.

The liver injury does not build up gradually and it is not proportional to how careful you have been. The published case describes exactly the pattern to watch for: a healthy young man, no other risk factors, who became progressively more tired, then itchy, then noticed dark urine, then yellowing of the eyes. That sequence — fatigue, then itching without a rash, then dark urine, then jaundice — is the one to act on. Stop and get a liver panel that week.

Being idiosyncratic, this cannot be avoided by using less or by cycling sensibly. That is precisely what makes it hard to reason about: nothing you do changes your odds much, and the absence of a problem so far tells you nothing about next month.

Interactions and combinations

RAD-140 is not a CNS depressant and does not carry the respiratory risk that dominates the opioid and GABA pages on this site.

The interaction that matters is anything else that stresses the liver: alcohol, regular paracetamol/acetaminophen, oral anabolic steroids, and the other SARMs it is routinely stacked with. Stacking is close to universal here, and it has a specific consequence — when someone does develop liver injury on a stack of four compounds from three vendors, nobody can determine which one did it, including the doctors treating them.

Cardarine is commonly sold and stacked with RAD-140 and is a completely different kind of risk. Do not carry a judgement about one across to the other.

RAD-140 is prohibited in all tested sport and is detectable well after the last use.

If you’re already using it

There is no withdrawal and no need to come off gradually. Stopping is simply stopping.

Get bloods, and get them before you feel bad. Testosterone, LH and FSH, and a liver panel. If you never established a baseline, get the panel anyway — a doctor can still tell a suppressed axis from a normal one.

Know the liver sequence — fatigue, itching without a rash, dark urine, pale stools, yellow eyes — and treat it as a stop-this-week signal rather than something to monitor.

If you feel flat, exhausted and low-libido for more than a few weeks after stopping, get it investigated. Suppression that is not recovering is a treatable medical problem. The trap is that the only thing that reliably makes you feel better in the short term is starting another cycle.

Tell your doctor what you took, by name. Many have not heard of RAD-140; “a selective androgen receptor modulator, an unapproved experimental drug that acts on the androgen receptor” is the phrase that gets you understood. It will not appear on any routine drug screen.

This page has not yet been reviewed by a clinician. It was written from the published literature and every claim is cited, but no named medical professional has checked it. We say so here rather than let a missing byline read as an implicit one.

Last reviewed 7 September 2026. Found something wrong? Corrections are published, not silently edited.