A SARM, or selective androgen receptor modulator, is a synthetic drug designed to mimic some of the muscle-building effects of testosterone while targeting specific tissues like muscle and bone. Unlike traditional anabolic steroids, which flood the entire body with androgenic activity, SARMs are engineered to be selective, activating androgen receptors in some tissues while largely sparing others like the prostate or skin. No SARM has been approved for human use by the FDA or any other regulatory body. They remain investigational drugs, meaning they are still in the experimental phase of development.
How SARMs Work in the Body
Your body’s androgen receptors respond to hormones like testosterone by switching on genes involved in building muscle, maintaining bone density, and developing male sex characteristics. When testosterone binds to an androgen receptor, it triggers a cascade of activity across many tissues at once. SARMs bind to those same receptors but cause the receptor to fold into a slightly different shape. That different shape changes which helper proteins (called coregulators) attach to the receptor, and that in turn changes which genes get activated. Because different tissues contain different sets of coregulators, a SARM can switch on muscle-building genes in skeletal muscle while staying relatively quiet in tissues like the prostate gland.
There’s a second reason for this selectivity. Testosterone gets converted into a more potent form called DHT in certain tissues, particularly the prostate, skin, and hair follicles. That conversion amplifies its effects in those areas. Nonsteroidal SARMs cannot be converted into DHT or into estrogen, which means they don’t trigger the hair loss, acne, or prostate enlargement commonly associated with anabolic steroids. At least, that’s the theory. In practice, the degree of selectivity varies between compounds and hasn’t been fully proven in long-term human studies.
Common SARM Compounds
SARMs are typically identified by alphanumeric codes rather than brand names, since none have completed the approval process to earn a generic drug name most people would recognize. The most widely discussed compounds include:
- Ostarine (MK-2866 or enobosarm): The most extensively studied SARM in clinical trials. It has been tested in cancer patients experiencing muscle wasting and showed significant increases in lean body mass over 16 weeks.
- Ligandrol (LGD-4033): Developed originally for muscle wasting and osteoporosis. A clinical trial in healthy young men showed dose-dependent gains in lean body mass and leg press strength over 21 days, and the drug was generally well tolerated at those doses.
- Testolone (RAD-140): One of the more potent SARMs, originally developed for muscle wasting and breast cancer. It has gained popularity in bodybuilding circles but is also one of the compounds most frequently linked to liver injury case reports.
- Andarine (S-4): An earlier SARM known for a distinctive side effect of yellow-tinted vision, along with testosterone suppression.
Several products commonly sold alongside SARMs are not actually SARMs at all. Ibutamoren (MK-677) stimulates growth hormone secretion, and GW501516 (Cardarine) activates a completely different receptor involved in fat metabolism. Both are unapproved drugs frequently mislabeled and bundled with SARMs in online marketplaces.
What SARMs Are Being Studied For
The medical conditions driving SARM research center on muscle and bone loss. Cancer cachexia, the severe muscle wasting that accompanies many cancers, is one of the most active areas. A phase 2 trial of enobosarm in cancer patients showed meaningful gains in lean body mass, and a follow-up study in lung cancer patients showed improvements in lean mass, strength, and survival, though it didn’t hit its primary study goals.
Osteoporosis is another target. Preclinical studies with LGD-4033 demonstrated improvements in bone mineral density, bone formation, and bone strength. Osteoporosis is considered a particularly promising pathway for SARM development because the regulatory process for bone drugs is well established, with clear benchmarks for measuring effectiveness. Other conditions under investigation include age-related muscle loss (sarcopenia), anemia, and wound healing. None of these applications have progressed to approved treatments.
How SARMs Differ From Anabolic Steroids
Traditional anabolic steroids are modified versions of testosterone itself. They activate androgen receptors throughout the body indiscriminately, which is why they build muscle effectively but also cause a long list of side effects: liver damage, heart problems, acne, hair loss, prostate enlargement, and hormonal disruption. SARMs are nonsteroidal compounds with a completely different chemical structure. They were designed from the ground up to be tissue-selective, acting as full activators in muscle and bone while behaving as partial activators or even blockers in other tissues.
In practical terms, this means SARMs are generally less potent than steroids for raw muscle growth, but they were intended to carry fewer androgenic side effects. That said, “fewer” does not mean “none.” SARMs still suppress the body’s natural testosterone production, still affect the liver, and still alter cholesterol levels. The gap between SARMs and steroids in terms of safety is narrower than early marketing suggested.
Known Health Risks
Liver Damage
SARMs can disrupt liver function through oxidative stress, changes in fat metabolism, and direct damage to liver cells. Case reports have documented outcomes ranging from mild enzyme elevations to jaundice, bile flow obstruction, and acute liver failure. In one documented case involving RAD-140, a patient’s liver enzyme levels rose to over 50 times the normal upper limit. Ligandrol and RAD-140 are the two compounds most frequently implicated in liver injury reports. Symptoms typically include fatigue, nausea, abdominal pain, and yellowing of the skin or eyes.
Cholesterol Changes
A 12-week clinical study found that SARM use significantly suppressed HDL cholesterol (the protective kind) in a dose-dependent manner. The drug also reduced levels of a key protein that helps HDL do its job of clearing cholesterol from arteries. LDL cholesterol and triglycerides were not significantly affected, but the drop in HDL alone shifts the balance toward increased cardiovascular risk, particularly with repeated or prolonged cycles.
Testosterone Suppression
Even at relatively low doses, SARMs suppress the body’s own testosterone production. In a clinical trial of Ligandrol at just 1 mg per day, both free testosterone and follicle-stimulating hormone dropped significantly. Hormone levels returned to normal after the drug was stopped, but the timeline for full recovery varies. In bodybuilding communities, users commonly report needing about four weeks of post-cycle recovery, and side effects during and after a cycle can include fatigue, low libido, headaches, and nausea, all consistent with low testosterone.
Other Reported Effects
The FDA has specifically warned that SARM-containing products carry risks of heart attack, stroke, psychosis or hallucinations, sleep disturbances, sexual dysfunction, infertility, pregnancy miscarriage, and testicular shrinkage. Life-threatening reactions requiring hospitalization have been reported.
Legal and Regulatory Status
SARMs occupy an unusual legal gray zone. They are not approved by the FDA for any medical use. They cannot be legally prescribed by a doctor. They are not dietary supplements, despite being widely marketed as such online. The FDA has issued explicit warnings that these products are unapproved drugs that have not been reviewed for safety or effectiveness, and has urged consumers not to purchase them.
In competitive sports, SARMs are banned without exception. The World Anti-Doping Agency lists them under “Other Anabolic Agents” on its prohibited list, and they are banned at all times, both in and out of competition, at every level from elite to recreational. Athletes have been suspended after testing positive for SARMs, sometimes claiming they unknowingly consumed contaminated supplements.
Product Quality Is Unreliable
One of the most underappreciated risks of SARMs is that the products sold online frequently don’t contain what they claim. A study published in JAMA analyzed 44 products marketed as SARMs and purchased through the internet. Only 52% actually contained a SARM. Another 39% contained a different unapproved drug entirely. Nine percent contained no active compound at all. A full 25% contained substances not listed on the label, and 59% had quantities that didn’t match what was advertised. Four products even contained tamoxifen, a prescription breast cancer drug, without listing it.
This means that even someone who has weighed the risks and decided to use a SARM has no reliable way of knowing what they’re actually taking, how much of it is in each dose, or whether it’s been contaminated with something else entirely. The lack of manufacturing oversight makes every purchase a gamble on both identity and purity.