What is it?
What ostarine is
1Ostarine is the research compound enobosarm, also known as MK-2866 or GTx-024. It activates androgen receptors and was investigated for muscle-related clinical outcomes. A compound being called a SARM does not establish cognitive benefit or supplement safety.
Names, aliases and forms
Mechanisms of action
Selective androgen receptor modulator
2Ostarine is a nonsteroidal androgen-receptor modulator developed for tissue-selective anabolic effects. Selectivity describes pharmacology; it does not mean that liver, lipid or hormone effects are absent.
Potential effects and evidence map
Human phase 2 studies provide population-specific lean-mass signals, with less certain translation to meaningful physical function. These trials did not establish cognitive enhancement, young-adult bodybuilding benefits or a safe consumer cycle. Clinical biomarker changes and postmarketing reports require safety context.
Small trials provide muscle-mass signals in older or cancer populations; healthy-user athletic and cognitive benefits remain unestablished.
Typical dosages and timing
The older-adult study compared four oral doses (0.1, 0.3, 1 and 3 mg daily) with placebo. The separate cancer trial used 1 or 3 mg daily. These are study exposures, not a recommended consumer dosage or a basis for post-cycle therapy.
Timing & effect horizon
The featured window comes from the older-adult trial. It describes when repeated-use outcomes were assessed, not how soon a person should feel an effect, a safe cycle length, or an elimination The time for blood levels to fall by half during the final elimination phase.Source. No featured onset or half-life is asserted here.
Safety, side effects and risk profile
As of October 2026, US FDA excludes SARMs from lawful dietary-supplement marketing; WADA 2026 prohibits ostarine at all times in governed sport.
Ostarine/enobosarm and other SARMs have published liver-injury case reports and adverse-event analyses.
The older-adult trial found lower total testosterone and SHBG in men, without significant free-testosterone, LH or FSH differences versus placebo.
Dose-related HDL reductions occurred in the older-adult trial; cardiovascular event rates were not established.
Pregnancy, breastfeeding and attempts to conceive require particular caution: safe reproductive exposure is not established, and FDA reports pregnancy and fertility concerns with SARMs.
Consumer stacking and post-cycle regimens lack validated interaction and safety data.
Retail SARM product identity and dose may not match labels, making self-directed risk hard to assess.
An ostarine case report describes marked cholestatic liver injury after nonmedical use. Case reports cannot estimate frequency or fully exclude retail-product confounding. The signal is clinically important, but it does not show that every user develops liver injury.
In the older-adult trial, total testosterone and sex hormone-binding globulin fell in men at higher study doses. Free testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) did not differ significantly from placebo. A lower total testosterone result alone does not prove the same degree of endocrine suppression in every user.
HDL cholesterol fell with increasing dose in the older-adult trial. That biomarker change does not quantify heart-attack or stroke incidence. FDA separately warns about serious cardiovascular events with SARM products; individual risk cannot be calculated from these small trials.
Interactions and cautions
Reliable interaction trials for consumer ostarine combinations are lacking. Combining SARMs with anabolic agents or other performance drugs complicates attribution of liver, hormonal and cardiovascular effects. A post-cycle regimen is not an established safeguard against these harms.
Legal and regulatory status
As of 18 October 2026, FDA states that SARMs cannot legally be marketed in the United States as dietary supplements or drugs. A research-use label does not make consumer sale an approved use. Other countries have their own rules for sale, import and possession; US status should not be generalized worldwide.
The WADA 2026 Prohibited List names enobosarm (ostarine) in S1.2, Other Anabolic Agents, prohibited at all times in WADA-governed sport. This sporting restriction is separate from national consumer law.
How it compares
Enobosarm, MK-2866 and GTx-024 identify ostarine. AC-262536 (AC-262, Accadrine) is a different investigational SARM. A listing advertised as an Ostarine alternative does not establish that it contains ostarine; its dose or price cannot be compared as the same ingredient.
Lean mass measured by dual-energy X-ray absorptiometry (DXA) is not the same outcome as stronger lifts, durable athletic performance or cognition. The cancer trial included 159 participants for safety but only 100 in its evaluable efficacy analysis; illness, attrition and sponsorship limit generalization. Its findings do not validate a healthy-user cycle.
Practical buying and quality notes
- A 2017 analysis of 44 internet products marketed as SARMs found only 23 contained a SARM; 11 contained an unlisted substance, and only 18 matched their labelled quantity. This historical sample demonstrates a quality problem, not the failure rate of every current retailer.4
- Confirm enobosarm identity before comparing capsule, powder or solution listings. A capsule count, total powder mass and solution concentration are different quantities. Do not infer ostarine milligrams from an alternative compound or use a stale catalog amount as a dosing recommendation.6
- A useful report identifies the tested batch, analytical method and measured compound amount. Identity and quantity testing can address label uncertainty; it cannot establish that a product is safe, approved or suitable for sport. Price alone answers none of those questions.4
FAQ
Is ostarine a nootropic?
2No established human evidence supports memory, attention or productivity benefits. The cited trials examined muscle-related outcomes in selected populations, not cognitive enhancement.
Is ostarine allowed in sport?
7No in WADA-governed sport: the 2026 list prohibits enobosarm (ostarine) at all times, including outside competition.
What should buyers check first?
6Check the actual compound first: AC-262 alternatives are not ostarine. Then distinguish labelled quantity from independently measured content and review the local legal and sporting rules. A listing is evidence of availability, not proof of efficacy or safety.
References
- PubChem. Ostarine. Compound CID 11326715.
- Dalton JT, Barnette KG, Bohl CE, Hancock ML, Rodriguez D, et al. The selective androgen receptor modulator GTx-024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women. J Cachexia Sarcopenia Muscle. 2011;2(3):153-161.
- Dobs AS, Boccia RV, Croot CC, Gabrail NY, Dalton JT, et al. Effects of enobosarm on muscle wasting and physical function in patients with cancer: a double-blind, randomised controlled phase 2 trial. Lancet Oncol. 2013;14(4):335-345.
- Van Wagoner RM, Eichner A, Bhasin S, Deuster PA, Eichner D. Chemical Composition and Labeling of Substances Marketed as Selective Androgen Receptor Modulators and Sold via the Internet. JAMA. 2017;318(20):2004-2010.
- US Food and Drug Administration. Certain bodybuilding products put consumers at risk for heart attack, stroke, serious liver damage and more. Accessed 18 October 2026.
- Operation Supplement Safety. SARMs: What's the Harm? Updated 19 August 2025; accessed 18 October 2026.
- World Anti-Doping Agency. The Prohibited List, 2026 List effective 1 January 2026.
- Leciejewska N, et al. Selective androgen receptor modulator use and related adverse events including drug-induced liver injury: Analysis of suspected cases. Eur J Clin Pharmacol. 2024;80:185-202.
- Bedi H, Hammond C, Sanders D, Yang HM, Yoshida EM. Drug-Induced Liver Injury From Enobosarm (Ostarine), a Selective Androgen Receptor Modulator. ACG Case Rep J. 2021;8(1):e00518.