Is ostarine a steroid? MK-2866 classification and legal status

What counts as a steroid in law

The statutory text: the Controlled Substances Act defines an anabolic steroid as "any drug or hormonal substance, chemically and pharmacologically related to testosterone (other than estrogens, progestins, corticosteroids, and dehydroepiandrosterone)", then lists the compounds it covers.

Two conditions, both required: chemical relation and pharmacological relation. A compound that acts on the androgen receptor but shares no steroid chemistry fails the first test.

Where ostarine lands: outside that definition. The enumerated list inside the statutory definition at 21 U.S.C. 802(41)(A) does not name it, and neither does the anabolic-steroid entry in the federal schedules at 21 CFR 1308.13(f), which schedules any substance meeting that same statutory definition. We searched both texts for ostarine, enobosarm and MK-2866 and found no match. Not being scheduled is a different statement from being lawful to sell, and the two get conflated constantly.

What ostarine is

The class: the developer described GTx-024, the compound published as enobosarm, as a nonsteroidal selective androgen receptor modulator with tissue-selective anabolic effects in muscle and bone, sparing other androgen-responsive tissue (Dalton, 2011).

The names: ostarine, enobosarm, MK-2866 and GTx-024 all point at the same molecule. Retail listings favor the first and third; the published literature uses the second.

The development history: it went through company-run phase 2 trials in muscle wasting, which is precisely why FDA can exclude it from the supplement definition. Public clinical investigation is the trigger.

The status today: in the United States, FDA has told sellers that products labeled to contain it are new drugs with no approved application and that SARMs cannot be legally marketed as a supplement or a drug. We have run no search of other countries' registers, so we make no claim about them.

Is ostarine a steroid?

No. It is nonsteroidal by chemistry and it sits outside the statutory definition of an anabolic steroid, which requires a drug or hormonal substance chemically and pharmacologically related to testosterone. What it shares with a steroid is the receptor it binds, and that is where the resemblance stops.

Why people assume otherwise: the marketing borrows steroid language, and FDA's own consumer notice describes SARMs as chemical substances that mimic the effects of testosterone and anabolic steroids. Mimicking an effect is not the same as being in the class.

Is ostarine legal in the United States?

Not as a supplement, and not as a drug. In a warning letter dated 23 October 2017, FDA told a seller that products labeled to contain ostarine and LGD-4033 do not meet the definition of a dietary supplement in section 201(ff) of the Federal Food, Drug, and Cosmetic Act, because section 201(ff)(3)(B)(ii) excludes an article authorized for investigation as a new drug once substantial clinical investigations have been instituted and made public.

The second half of the same letter: because the marketing claimed effects on body structure, the products were drugs under section 201(g)(1)(C), then new drugs under 201(p) with no approved application, then misbranded for lacking adequate directions for use.

The current agency line: FDA's consumer notice, current as of 26 April 2023, states that SARMs cannot be legally marketed in the United States as a dietary supplement or a drug at this time.

What "research use only" did in one later letter: not enough to change the outcome. In a December 2025 warning letter to a different seller, covering LGD-4033, RAD-140, MK-677 and S-23 rather than ostarine, FDA treated the products as unapproved new drugs despite labeling that read "RESEARCH COMPOUND" and "NOT FOR HUM[AN]", on the basis of the website evidence of intended use.

Did the SARMs Control Act ever pass?

No, and neither did the version before it. S. 2895, the SARMs Control Act of 2019, was introduced on 19 November 2019 in the 116th Congress. It would have added a defined SARM category to Schedule III of the Controlled Substances Act, naming ostarine and enobosarm first in its list alongside LGD-4033, LGD-3303, LY2452473, RAD-140, andarine, BMS-564929, LG-121071 and S-23. Its official bill-status record carries nothing dated after the day it was introduced: the latest action reads "Read twice and referred to the Committee on the Judiciary", and the record shows no law. S. 2742, the SARMs Control Act of 2018, was introduced on 24 April 2018 in the 115th Congress with the same structure, and its status record ends the same way on its own introduction date.

What that does and does not settle: both bills proposed to add SARMs to Schedule III and neither became law, so ostarine is not scheduled today and the enforcement that does exist runs through drug law instead. Neither the bill texts nor the status records state why either one stopped, so this page does not supply a reason for it.

Is ostarine banned in sport?

Yes, in and out of competition. The 2026 WADA Prohibited List names enobosarm (ostarine) at S1.2, other anabolic agents, in the entry that reads "selective androgen receptor modulators [SARMs, e.g. andarine, enobosarm (ostarine), LGD-4033 (ligandrol), RAD140, S-23 and YK-11]". Every substance in the S1 class is a non-specified substance, and the list has been in force since 1 January 2026.

The scope of "including, but not limited to": the list names six SARMs and covers the class. A compound not printed by name is not thereby permitted.

What is in a product sold as ostarine?

One published analysis answers this for its own sample, and that sample was not ostarine-specific. In a chemical analysis of 44 products bought online as SARMs generally, only 23 contained any SARM at all, 17 contained a different unapproved drug, and 4 contained no active compound. The amount on the label matched the amount found in only 18 of the 44, and 11 held substances the label never mentioned (Van Wagoner, 2017).

What that sample showed: for these 44 products, nothing in the supply chain was making the label match the contents. The analysis measured identity and amount against the label; it did not examine any manufacturer's specifications, so we make no claim about what does or does not sit behind an individual product.

What the record still leaves open

Four items, none of them small:

• Healthy-population effect. The published randomized data sits in older adults and in cancer-associated wasting, not in young healthy users.
• Duration. The two trials on this page ran 12 weeks and up to 113 days. Neither describes longer use, and we have not run a systematic search of the wider literature, so this is a limit of what is reported here rather than a ceiling on the published record.
• Liver signal. FDA cites liver injury and acute liver failure among reported harms, and states the real number of adverse events is likely higher because reporting is voluntary and users may not connect symptoms to the product.
• Product identity. The 2017 analysis sampled products purchased between February and August 2016, so it is one snapshot of that market at that time.

How this page is sourced

Read at the source: the statutory definition comes from the United States Code and the federal schedules from the Code of Federal Regulations, both searched by name for this compound; the enforcement position from FDA letters and the agency's own consumer notice; the trial figures from the two published papers; the legislative history from each bill's own text and its official status record; and the sport classification from the official 2026 list text.

Eleven sources: three papers with DOIs and PubMed IDs, one statute, one regulation, two bills with their official status records, three FDA documents, and one international standard.

The standard: the full sourcing and citation-verification standard for this site, including who checks a page before it ships, lives on the methodology page.

Last reviewed: 29 July 2026.

1. 1

   Dalton JT, Barnette KG, Bohl CE, et al. The selective androgen receptor modulator GTx-024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women: results of a double-blind, placebo-controlled phase II trial. J Cachexia Sarcopenia Muscle. 2011;2(3):153-161. doi:10.1007/s13539-011-0034-6. PMID 22031847.

2. 2

   Dobs AS, Boccia RV, Croot CC, 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. doi:10.1016/S1470-2045(13)70055-X. PMID 23499390.

3. 3

   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. doi:10.1001/jama.2017.17069. PMID 29183075.

4. 4

   Definition of anabolic steroid, 21 U.S.C. section 802(41), including the enumerated list at 802(41)(A), searched for ostarine, enobosarm and MK-2866 with no match. Accessed 29 July 2026. govinfo.gov, 21 U.S.C. 802.

5. 5

   Schedules of controlled substances, Schedule III, 21 CFR 1308.13(f), anabolic steroids, searched for ostarine, enobosarm, MK-2866 and selective androgen receptor modulators with no match. Accessed 29 July 2026. ecfr.gov, 21 CFR 1308.13.

6. 6

   S. 2895, SARMs Control Act of 2019, 116th Congress, introduced 19 November 2019. Its official bill-status record carries no action dated after the introduction date, its latest action reads "Read twice and referred to the Committee on the Judiciary", and it records no law. Accessed 29 July 2026. govinfo.gov, BILLS-116s2895is. govinfo.gov, BILLSTATUS-116s2895.

7. 7

   S. 2742, SARMs Control Act of 2018, 115th Congress, introduced 24 April 2018. Its official bill-status record carries no action dated after the introduction date, its latest action reads "Read twice and referred to the Committee on the Judiciary", and it records no law. Accessed 29 July 2026. govinfo.gov, BILLS-115s2742is. govinfo.gov, BILLSTATUS-115s2742.

8. 8

   U.S. Food and Drug Administration. Warning letter to Panther Sports Nutrition, WL 535341, 23 October 2017. Accessed 27 July 2026. fda.gov warning letter 535341.

9. 9

   U.S. Food and Drug Administration. FDA warns of use of selective androgen receptor modulators (SARMs) among teens, young adults. Consumer update, content current as of 26 April 2023. Accessed 29 July 2026. fda.gov consumer update.

10. 10

    World Anti-Doping Agency. World Anti-Doping Code International Standard: Prohibited List 2026, section S1.2. Effective 1 January 2026. Accessed 29 July 2026. Re-checked 31 July 2026: an automated request for the list PDF returned HTTP 202 with an empty body, which is a bot challenge rather than a missing document, so this source could not be re-retrieved by script on that date. wada-ama.org, 2026 Prohibited List.

11. 11

    U.S. Food and Drug Administration. Warning letter to Prime Sports Nutrition, reference 719433, 12 December 2025. Accessed 29 July 2026. fda.gov warning letter 719433.

Related pages

Around this page: five neighboring pages on classification and on what a vial can be shown to contain.

• Is MK-677 a SARM: the compound sold beside ostarine that is not in the class at all.
• Cardarine (GW501516) explained: the third compound in the same retail bucket, and the toxicology record behind it.
• How to read a COA: what a certificate of analysis tests, and what it leaves untested.
• What an HPLC purity number misses: why a high percentage on paper answers a narrow question.
• The dose-math hub: the arithmetic section, for the pages where numbers do the work.

Where the next one lands: every new statute-and-label read goes out through The Decadewise briefing on the day it is finished.