A selective androgen receptor modulator binds the androgen receptor and acts on it selectively by tissue — the intent being anabolic activity in muscle and bone with less action elsewhere than testosterone produces. That is the whole definition, and it is the line that decides what belongs on this page.
Most of the confusion in this category is not about dosing or stacking. It is that half the compounds sold as SARMs are not SARMs, and the research people cite for one is research on a different one.
What Is Actually a SARM, and What Is Not
| Compound | Actually a SARM? | What it really is |
|---|---|---|
| RAD-140 (testolone) | Yes | Androgen receptor agonist. One first-in-human trial, in breast cancer patients. |
| LGD-4033 (ligandrol) | Yes | Androgen receptor agonist. Has been through randomised controlled trials. |
| Ostarine (MK-2866, enobosarm) | Yes | Androgen receptor agonist. The most clinically studied of the group. |
| Andarine (S-4) | Yes | Androgen receptor agonist. Largely abandoned in development. |
| MK-677 (ibutamoren) | No | Ghrelin receptor agonist. Raises the body's own growth hormone. Does not touch the androgen receptor. |
| GW501516 (cardarine) | No | PPAR-delta agonist. A metabolic compound, not an androgen one. |
| SR9009 (stenabolic) | No | Rev-ErbA agonist. Also not an androgen compound. |
The bottom three are on every SARM retailer's shelf and in most SARM articles. None of them is a SARM. This matters practically: if you read that "SARMs suppress testosterone" and you are taking MK-677, that sentence does not apply to you, and if you read that "SARMs are well studied" on the strength of the ostarine trials, that does not transfer to RAD-140.
What the Human Evidence Actually Covers
There is real clinical trial evidence in this category, and it is narrower than the marketing implies. A 2025 systematic review in Clinical Endocrinology gathered every randomised controlled trial of SARMs and physical performance: nine trials, 970 patients, mean age 57, mean follow-up 80 days. The six compounds covered were LGD-4033, PF-06260414, GSK2881078, GTx-024, MK-0773 and OPK-88004.
Two things follow from that list. First, the trials were mostly in older and clinical populations being studied for sarcopenia and cachexia — not healthy trained adults trying to add muscle. Second, RAD-140 is not on it. The most heavily marketed SARM in Ireland has no randomised performance trial at all, and its only human study was a phase 1 dose-escalation in 22 breast cancer patients whose most frequent adverse events were elevated AST (59.1%) and ALT (45.5%).
What the Case Reports Say
Alongside the trial literature there is a steadily growing record of harm, most of it from case reports rather than controlled data. A case report cannot tell you how likely something is; it can tell you the thing happens in real people.
- Liver injury. Drug-induced liver injury linked to RAD-140 has been published every year since 2020, including a severe case in Australian Prescriber after use for bodybuilding and a cholestatic case requiring corticosteroids.
- Cardiac events. Myocarditis, myopericarditis and heart failure have all been reported in RAD-140 users.
- Tendon rupture. Flagged alongside liver injury and myocarditis in a 2025 systematic review in the American Journal of Sports Medicine on SARM abuse in athletes.
- Suppression. Expected from the mechanism for any true SARM. Recovery of natural production is not guaranteed to be quick or complete.
The Purity Problem Comes First
Before any of the risks above apply, there is the question of whether the product contains the compound at all. A 2017 JAMA analysis bought 44 products sold online as SARMs and tested them in a WADA-accredited laboratory:
- 52% contained any SARM at all.
- 39% contained a different unapproved drug — ibutamoren, GW501516 and SR9009 among them.
- 9% contained no active compound whatsoever.
- 25% contained substances not listed on the label.
- 41% matched the amount of active compound the label claimed.
That last figure is the one to sit with. In roughly six products out of ten, the amount in the bottle was not the amount on the label. Any risk calculation you make about a specific compound is being made about a bottle whose contents you do not know.
Where Irish Law Sits
No SARM holds a medicinal licence from the Health Products Regulatory Authority or the European Medicines Agency. None is an approved ingredient in a food supplement under EU rules. Selling them for human consumption in Ireland is not permitted, which is why they are sold under research-chemical labelling — a statement about legal category, not about quality or purity.
They are not controlled substances under the Misuse of Drugs Acts. That is the distinction people usually mean when they say SARMs are "legal in Ireland": possession is not a criminal matter in the way it is for controlled drugs, but nothing about them is approved, tested for consumer sale, or supervised.
For anyone subject to testing, it is simple. SARMs are on the WADA prohibited list at all times, in and out of competition, with long detection windows.
My Own Position On This
I have used RAD-140, for eight weeks, and I have written up what that was actually like rather than pretending otherwise. I am on TRT, I had bloods done, and the risk calculation I made was mine and applies to my circumstances. It is not a recommendation and there are no doses on this site. If you're weighing up where these products actually get sourced in Ireland, see the HardCore Supplements review — same disclosure applies there.
What I would say to anyone reading this page for a decision: the research does not support what the shops claim, the product frequently is not what the label says, and the documented human record for the most popular compound in this category is a list of liver and cardiac case reports. That is not a scare paragraph, it is what the citations above contain.
Frequently Asked Questions
Is MK-677 a SARM?
No. It is a ghrelin receptor agonist that raises your own growth hormone output. It does not bind the androgen receptor. It is sold as a SARM almost everywhere, which is a retail habit rather than a fact. Full detail in the MK-677 research guide.
Are SARMs legal to buy in Ireland?
They are not licensed as medicines and not approved as supplement ingredients, so they cannot lawfully be sold for human consumption. They are not controlled substances, so possession is not a criminal matter. That gap is what the research-chemical label exists to sit in.
Which SARM has the most human research?
Ostarine (enobosarm), by a distance, followed by LGD-4033. Both have been through randomised controlled trials, mostly in clinical populations rather than healthy trained adults. RAD-140, which is the most marketed, has the least — one phase 1 trial in cancer patients.
Will liver supplements protect me?
There is no trial evidence that milk thistle, TUDCA or NAC prevents SARM-induced liver injury. Bloodwork tells you damage is happening; it does not stop it happening. Treating either as protection is the mistake.
Will SARMs show on a drugs test?
Yes. WADA prohibits them at all times, the assays are well established and detection windows are long.