YK-11 UK law vs WADA rules: two different questions

Written by Free Muscle · Published by a seller of these compounds · Last updated

People searching for "YK-11 UK" are usually asking two different questions that often get run together. The first is a question of UK law: where does the compound stand under UK medicines and novel foods legislation? The second is a question of sport: what do the World Anti-Doping Agency (WADA) rules say? The answers come from different sources, and a yes or no to one is not an answer to the other. This guide separates the two, using primary legislation and published studies, explains what a "research use only" label really means, shows how to tell a properly tested batch from an untested one, and then explains how ordering, batch testing and storage work at Free Muscle.

Key takeaways

  • YK-11 is a steroidal compound that researchers have described as a selective androgen receptor modulator (SARM). The YK-11 studies reviewed for this article are cell-culture studies, rodent studies, equine studies, a supplement-screening analysis and doping-control analysis. No human clinical trial of YK-11 appears in the literature reviewed for this article.
  • A 2024 review states that none of the SARMs it covered has been approved by the US Food and Drug Administration or the European Medicines Agency for pharmacotherapy (Leciejewska et al., 2024).
  • In sport, review authors report that SARMs were added to the World Anti-Doping Agency (WADA) Prohibited List in 2008 (Thevis and Schanzer, 2018). Anyone subject to anti-doping rules should check the current List directly.
  • A research use only label is a description, not evidence of identity, purity or legality.
  • A Certificate of Analysis (COA) from a named independent laboratory, matched to the batch number on the label, is the usual evidence of identity and purity for laboratory materials.
  • Research compounds sold by Free Muscle are supplied for laboratory research use only and are not for human consumption. They are not authorised as medicines by the MHRA, EMA or FDA, are not food supplements, and are sold only to adults aged 18 or over. Nothing on this page is medical or dosing advice.

This is general information, not legal advice and not medical advice.

There is no simple yes or no to the YK-11 UK legal question, and this article cannot give one. What it can do is point to primary legislation and to published reviews, so that readers can read the sources themselves. This is general information, not legal advice. Anyone who needs a firm answer for their own circumstances should ask a solicitor or the relevant regulator.

What the review literature says about approval

A 2024 review of adverse events states that, despite SARMs being in clinical trials, none has been approved by the US Food and Drug Administration or the European Medicines Agency for pharmacotherapy (Leciejewska et al., 2024). A 2018 review of doping-control analysis likewise noted that none of the SARMs it discussed had yet received full clinical approval (Thevis and Schanzer, 2018). Neither paper is a statement of UK law, and this article draws no legal conclusion from them.

Primary legislation

Two pieces of UK legislation are linked below so that readers can read the wording for themselves. Neither mentions YK-11 by name, and the pages linked here do not mention SARMs, so how they apply to any particular compound is a matter for regulators and courts, not for this article.

  • The Human Medicines Regulations 2012 define a "medicinal product" in regulation 2(1), including a substance that may be administered to human beings to restore, correct or modify a physiological function by a pharmacological, immunological or metabolic action. Regulation 46(1) says a person may not sell or supply, or offer to sell or supply, an unauthorised medicinal product; the regulation is subject to the exceptions set out in the Regulations themselves.
  • The retained novel foods Regulation (EU) 2015/2283, Article 6, provides that only novel foods authorised by the appropriate authority may be placed on the market within Great Britain as such or used in or on foods.

Anti-doping literature on SARMs

A review of doping-control analysis noted that SARMs were added to the WADA Prohibited List in 2008 and that numerous adverse analytical findings have been reported for various SARMs since (Thevis and Schanzer, 2018). The 2017 mass-spectrometry paper on YK-11 states that, because of their anabolic properties, the use of SARMs is prohibited in sports as regulated by WADA (Thevis et al., 2017). A 2021 supplement-screening paper described SARMs as having been on the WADA prohibited list for more than a decade (Lee JH et al., 2021).

These are descriptions of SARMs as a class in published papers. They are not a quotation of the current Prohibited List, which this article does not reproduce. Anyone subject to anti-doping rules should read the current WADA Prohibited List and their own anti-doping body's guidance directly.

The position for the other compounds we stock, side by side: Are SARMs legal in the UK? 2026 guide

What "research use only" means, and what it does not

As used on this site, the phrase "for research use only" refers to laboratory research use only. On its own it is a label, not a guarantee of anything.

What Free Muscle states about its research compounds

  • The material is sold for laboratory research use only, to customers aged 18 or over.
  • It is not a medicine and not a food supplement, and it is not for human consumption.
  • Nothing in the listing, the label or this guide is medical advice.
  • Every batch is assayed for identity and purity by an independent laboratory, and the Certificate of Analysis is available on request (see the batch testing section below).

What the phrase does not do

The wording alone should not be read as evidence of anything about legality or quality. That is why this guide concentrates on things that can be checked: the named laboratory, the batch number, the test method and the date.

It also does not turn any claim about benefits into a fact. This article does not state or imply that any compound performs a particular function in people. The published literature on YK-11 is laboratory and animal work, summarised in the next section.

What researchers say

This is the "what others say" section: published research and review authors, each cited. Anecdotal reports from individuals are not evidence, and none are used here. The laboratory studies below describe what happened to the named cells or animals in each experiment; the reviews describe what was reported in the patients or athletes they covered. None of this can be assumed to apply to the reader, and nothing here suggests that anyone should consume any compound.

Cell-culture findings on how YK-11 works

In an early study, YK-11 behaved as a partial agonist of the androgen receptor in a reporter-gene assay, speeding up the receptor's movement into the cell nucleus without triggering the receptor's amino/carboxyl-terminal interaction. In MDA-MB 453 cells it acted as a gene-selective agonist, meaning its effect relative to an androgen varied with the gene studied (Kanno et al., 2011). A later study in the same cell line found that dihydrotestosterone (DHT) and YK-11 produced different patterns of target-gene expression and AR recruitment to enhancer regions, and the authors' assays suggested different cofactor recruitment (Kanno et al., 2022).

One cell-culture study examined myogenic differentiation of C2C12 myoblasts. In that cell culture, YK-11 but not DHT induced follistatin, and the YK-11-linked muscle-cell differentiation was reversed by an anti-follistatin antibody (Kanno et al., 2013). The authors framed follistatin induction as important for the compound's anabolic effect in that system. Two caveats matter. This is cell culture only, and the abstract does not describe independent replication in animals or people. A separate mouse sepsis study described YK-11 as inhibiting myostatin and reported lower inflammatory markers and lower mortality in the septic mice (Lee SJ et al., 2021), but that is a single rodent model of infection and says nothing about healthy people.

Bone-related laboratory findings

In MC3T3-E1 mouse osteoblast cells, YK-11 and DHT accelerated cell proliferation and mineralisation, and the bone-formation markers osteoprotegerin and osteocalcin rose compared with untreated cells (Yatsu et al., 2018). A 2025 study reported that YK-11 promoted osteogenic differentiation of bone marrow-derived stem cells and, delivered in a hydrogel, promoted repair of cranial bone defects in rats, with these effects suppressed when the androgen receptor was inhibited (Wang et al., 2025).

Adverse and cautionary findings

The same literature contains warning signs. In a five-week study in male Wistar rats, YK-11 was associated with increased oxidative stress and impairment of mitochondrial function markers in the hippocampus, and combining it with swimming exercise prevented alterations in some mitochondrial markers but did not reverse the increased oxidative stress or the impaired mitochondrial respiratory chain and dynamics proteins (Dahleh et al., 2023). A second five-week rat study reported impaired aversive memory consolidation, down-regulated BDNF/TrkB/CREB signalling and raised hippocampal IL-1 beta and IL-6, and its authors said the findings challenge the common perception that SARMs have minimal side effects (Dahleh et al., 2024).

No human trial of YK-11 appears in the literature reviewed here, so the nearest human safety data come from other SARMs. A systematic review of 33 studies (2,136 patients, of whom 1,447 were exposed to a SARM) found 15 drug-induced liver injury case reports and a mean 7.1% rate of elevated ALT across the trials (Vignali et al., 2023). Another review identified 20 reports of adverse events since 2020, mostly drug-induced liver injury, and noted that data on dosage and purity of the products involved were limited (Leciejewska et al., 2024). A systematic review of 72 articles estimated athlete prevalence at 1% to 3% and said most SARMs bought online were shown to be contaminated with other substances (Vasireddi et al., 2025).

Analytical chemistry: why testing matters

Doping-control laboratories have characterised YK-11 by mass spectrometry (Thevis et al., 2017), mapped its metabolites in horse urine and plasma after oral administration (Harding et al., 2023) and detected it in horse mane hair, where it appeared to arrive mainly through sweat or sebum (So et al., 2025). A further letter (Sobolevsky et al., 2024) is titled as describing detection of YK-11 in a doping control sample; PubMed lists no abstract, so its details are not summarised here. These papers establish that the compound can be detected. They say nothing about benefit or safety.

One analytical paper bears on quality testing. A 2021 method-validation study applied its LC-MS/MS screening method to 60 dietary supplements obtained online and directly from international vendors in 2020, and found YK-11, not declared on the label, in some products. It also reported that YK-11 is easily hydrolysed in just a few hours (Lee JH et al., 2021). The authors reported that hydrolysed YK-11 was confirmed under acidic conditions; the abstract does not state the conditions or say how this applies to stored capsules.

Evidence gaps, in one list

  • In the sources reviewed for this article, no human clinical trial of YK-11 appears.
  • In the sources reviewed for this article, no human pharmacokinetic or toxicology data for YK-11 appear, so nothing can be assumed about an oral capsule.
  • The follistatin finding rests on one cell-culture study (Kanno et al., 2013), and the only myostatin experiment in the sources reviewed is a single mouse model of sepsis (Lee SJ et al., 2021).
  • In the sources reviewed for this article, none of the abstracts reports independent replication of the follistatin cell findings.
  • Doping-control papers establish detection, not benefit or safety.

For the wider SARM background, the 2026 SARM research guide covers the compound class in general terms.

How to judge quality: the Certificate of Analysis explained

A Certificate of Analysis is a report from a laboratory describing what it found when it tested a specific batch. Two terms are worth defining. Identity asks whether the compound is what the label says. Purity asks what proportion of the material is that compound rather than something else. The usual methods are HPLC (high-performance liquid chromatography, which separates the components of a sample and measures each) and mass spectrometry (which measures molecular mass and fragments to confirm structure). For a deeper walk-through, see how to read a Certificate of Analysis.

What to check What it tells you Red flag
Named laboratory Who ran the test, and whether an outside party can be asked to confirm it No laboratory named, or a logo with no contact route
Batch number matches the label That the report describes the bottle in front of you, not a different lot Batch number missing, or different from the one on the bottle
Product name and compound identity That the compound tested is the compound listed Generic wording such as "SARM blend", or a different compound name
Identity method (mass spectrometry, HPLC retention match) Whether structure was actually confirmed against a reference Purity percentage given but no identity method stated
Purity result (HPLC area percentage) How much of the sample is the target compound by that method A round figure with no chromatogram, or results that look edited
Test date When the batch was assayed, which matters for an unstable compound No date, or a date long before the stated manufacture
Quantity per unit, where tested Whether the declared amount matches the measured amount Declared strength that cannot be reconciled with the pack

The test date is worth checking, for the reason given in the analytical section above (Lee JH et al., 2021). A report cannot show what has happened to a bottle since it was tested, which is one more reason the batch number on the label matters.

How batch testing works at Free Muscle

Every Free Muscle batch of research compounds is assayed for identity and purity by Janoshik Analytical, an independent laboratory. The Certificate of Analysis for a batch is sent on request. To ask for one, email the batch number printed on the label together with the product name. The full process is described on the lab tests page, and the background on the laboratory is in what Janoshik Analytical is.

Batch testing applies to the YK-11 10mg, 60 capsules listing as to the other research compounds.

A COA does not make a compound a medicine, and it does not change the legal and anti-doping points set out above. It is evidence about the contents of a batch, and nothing more.

How to order from Free Muscle, step by step

These are the steps for a YK-11 UK order, from choosing the listing to requesting the Certificate of Analysis for the batch.

  1. Choose the listing. The YK-11 10mg, 60 capsules listing is the laboratory material this guide refers to. The wider SARMs collection shows the other listed research compounds.
  2. Age. Research compounds are sold only to customers aged 18 or over.
  3. Delivery. UK delivery is free and tracked, sent in plain packaging. Standard UK delivery takes 2 to 5 working days, and orders placed before 2pm UK time Monday to Friday are processed the same working day. Details are on the shipping page.
  4. Check the label on arrival. The batch number is printed on the label. Keep a note of it with the product name.
  5. Request the COA. Email the batch number and product name, as described in the batch testing section above.
  6. Returns. Unopened items in their original packaging can be returned within 30 days, as set out in the guarantee page. Apparel returns follow the refund policy.

Reading the strength and pack size on a label

This guide uses the YK-11 10mg, 60 capsules listing as its worked example: the listing names a strength of 10mg per capsule and a pack of 60 capsules. Other listings may differ, so always read the strength and capsule count on the label of the product in front of you.

One practical point follows from this: if a COA reports a quantity, it should be reconcilable with the strength and count on the label; a mismatch is a reason to query the batch with the seller. Readers comparing different compound families may find the SARMs versus peptides overview useful for context on how those categories differ.

Storage and handling of laboratory materials

These are general principles of good laboratory practice for any research material, not instructions specific to a person or to a product's intended effect.

  • Keep it sealed. Keep the container closed in its original packaging until it is needed for laboratory work.
  • Follow the supplier's documentation. Check the label and any supplier documentation for storage conditions. The analytical section above notes a stability observation from one study (Lee JH et al., 2021); its abstract gives no storage conditions, so this article does not set any.
  • Labelled. Keep the batch number and product name legible on the container, and record them in a log. This is what lets you request the right COA later.
  • Separate and secure. Store laboratory materials away from food and drink, and out of reach of children and pets.
  • Record keeping. Note the date received and the date opened.

Anyone unsure how to handle a laboratory material safely should consult the supplier's documentation and their own institution's safety guidance.

Frequently asked questions

Is YK-11 legal in the UK?

This guide cannot give legal advice on the YK-11 UK question. A 2024 review states that none of the SARMs it covered has been approved by the US FDA or the European Medicines Agency for pharmacotherapy (Leciejewska et al., 2024), and the primary legislation is linked in the legal section above. Free Muscle sells YK-11 for laboratory research use only, not for human consumption. Anyone needing a firm answer should consult a solicitor.

Is YK-11 banned in sport in the UK?

A 2017 doping-control paper on YK-11 states that the use of SARMs is prohibited in sports as regulated by WADA (Thevis et al., 2017). This guide does not reproduce the current Prohibited List, so anyone subject to anti-doping rules should check the current List directly.

Are UK law and WADA rules the same question for YK-11?

No. They are two different questions answered by two different sets of sources. UK law is a matter of primary legislation, such as the Human Medicines Regulations 2012 and the retained novel foods Regulation (EU) 2015/2283, both linked in the legal section above; neither mentions YK-11 by name, and how they apply to any particular compound is a matter for regulators and courts. The WADA position is an anti-doping rule for sport: published reviews report that SARMs were added to the WADA Prohibited List in 2008 (Thevis and Schanzer, 2018), and the current List should be read directly. A Certificate of Analysis changes neither answer. This is general information, not legal advice.

What does "research use only" mean?

It means the material is sold for laboratory research, to customers aged 18 or over, and is not a medicine, food supplement or product for human consumption. The wording on its own is not evidence of legality or quality, so it should be read alongside evidence such as a COA.

What is a Certificate of Analysis?

It is a laboratory report on a specific batch. It should name the laboratory, give the batch number and product name, state the test methods (for example HPLC and mass spectrometry), and report identity and purity results with a date.

How do I get the COA for my batch?

Email Free Muscle with the batch number printed on the label and the product name. The process for requesting a COA for a YK-11 order is described on the lab tests page.

Who tests Free Muscle batches?

Every batch of research compounds is assayed for identity and purity by Janoshik Analytical, an independent laboratory.

How long does UK delivery take?

Standard UK delivery takes 2 to 5 working days, it is free and tracked, and parcels are sent in plain packaging. Orders placed before 2pm UK time Monday to Friday are processed the same working day.

Can I return an order?

Unopened items in their original packaging can be returned within 30 days. See the guarantee page for details.

Is there an age limit?

Yes. Research compounds are sold only to customers aged 18 or over.

Has YK-11 been tested in humans?

No human clinical trial of YK-11 has been published in the sources reviewed for this article. The YK-11 studies reviewed are cell-culture studies, rodent studies, equine studies, a supplement-screening analysis and doping-control analysis; the human safety data cited come from other SARMs.

Why does purity testing matter for YK-11?

A 2021 method-validation study applied its LC-MS/MS screening method to 60 dietary supplements obtained online and directly from international vendors in 2020, and found YK-11, not declared on the label, in some products (Lee JH et al., 2021). The authors reported that YK-11 is easily hydrolysed in just a few hours; the abstract does not state the conditions or say how this applies to stored capsules.

Sources

  1. Kanno Y, Hikosaka R, Zhang SY, et al. (17alpha,20E)-17,20-[(1-methoxyethylidene)bis(oxy)]-3-oxo-19-norpregna-4,20-diene-21-carboxylic acid methyl ester (YK11) is a partial agonist of the androgen receptor. Biol Pharm Bull. 2011;34(3):318-23. doi:10.1248/bpb.34.318 PMID 21372378
  2. Kanno Y, Ota R, Someya K, et al. Selective androgen receptor modulator, YK11, regulates myogenic differentiation of C2C12 myoblasts by follistatin expression. Biol Pharm Bull. 2013;36(9):1460-5. doi:10.1248/bpb.b13-00231 PMID 23995658
  3. Kanno Y, Saito N, Saito R, et al. Differential DNA-binding and cofactor recruitment are possible determinants of the synthetic steroid YK11-dependent gene expression by androgen receptor in breast cancer MDA-MB 453 cells. Exp Cell Res. 2022;419(2):113333. doi:10.1016/j.yexcr.2022.113333 PMID 36030969
  4. Yatsu T, Kusakabe T, Kato K, et al. Selective androgen receptor modulator, YK11, up-regulates osteoblastic proliferation and differentiation in MC3T3-E1 cells. Biol Pharm Bull. 2018;41(3):394-398. doi:10.1248/bpb.b17-00748 PMID 29491216
  5. Wang R, Zhong Y, Du Q, et al. YK11 promotes osteogenic differentiation of BMSCs and repair of bone defects. J Mol Endocrinol. 2025;74(2). doi:10.1530/JME-24-0073 PMID 39660819
  6. Dahleh MMM, Bortolotto VC, Guerra GP, et al. YK11 induces oxidative stress and mitochondrial dysfunction in hippocampus: the interplay between a selective androgen receptor modulator (SARM) and exercise. J Steroid Biochem Mol Biol. 2023;233:106364. doi:10.1016/j.jsbmb.2023.106364 PMID 37468001
  7. Dahleh MMM, Bortolotto VC, Boeira SP, et al. [...] How Selective Androgen Receptor Modulator (SARM) YK11 impact hippocampal function: In silico, in vivo, and ex vivo perspectives. Chem Biol Interact. 2024;394:110971. doi:10.1016/j.cbi.2024.110971 PMID 38521455
  8. Lee SJ, Gharbi A, Shin JE, et al. Myostatin inhibitor YK11 as a preventative health supplement for bacterial sepsis [title as published]. Biochem Biophys Res Commun. 2021;543:1-7. doi:10.1016/j.bbrc.2021.01.030 PMID 33588136
  9. Thevis M, Piper T, Dib J, et al. Mass spectrometric characterization of the selective androgen receptor modulator (SARM) YK-11 for doping control purposes. Rapid Commun Mass Spectrom. 2017;31(14):1175-1183. doi:10.1002/rcm.7886 PMID 28440570
  10. Harding C, Viljanto M, Habershon-Butcher J, et al. Equine metabolism of the selective androgen receptor modulator YK-11 in urine and plasma following oral administration. Drug Test Anal. 2023;15(4):388-407. doi:10.1002/dta.3425 PMID 36519889
  11. So YM, Kong FK, Kwok WH, et al. Detection of nonsteroidal and steroidal selective androgen receptor modulators in equine hair after oral administrations. Drug Test Anal. 2025;17(5):655-662. doi:10.1002/dta.3772 PMID 39001560
  12. Sobolevsky T, Kucherova Y, Ahrens B. Detection of selective androgen receptor modulator YK-11 in a doping control sample. Drug Test Anal. 2024;16(6):655-660. doi:10.1002/dta.3604 PMID 37946705
  13. Thevis M, Schanzer W. Detection of SARMs in doping control analysis. Mol Cell Endocrinol. 2018;464:34-45. doi:10.1016/j.mce.2017.01.040 PMID 28137616
  14. Lee JH, Han JH, Jung EJ, et al. Development and validation of liquid chromatography-tandem mass spectrometry method for screening six selective androgen receptor modulators in dietary supplements. Food Addit Contam Part A. 2021;38(7):1075-1086. doi:10.1080/19440049.2021.1906954 PMID 33934684
  15. Leciejewska N, Jedrejko K, Gomez-Renaud VM, 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(2):185-202. doi:10.1007/s00228-023-03592-3 PMID 38059982
  16. Vignali JD, Pak KC, Beverley HR, et al. Systematic review of safety of selective androgen receptor modulators in healthy adults: implications for recreational users. J Xenobiot. 2023;13(2):218-236. doi:10.3390/jox13020017 PMID 37218811
  17. Vasireddi N, Hahamyan HA, Gould HP, et al. Athlete selective androgen receptor modulators abuse: a systematic review. Am J Sports Med. 2025;53(4):999-1009. doi:10.1177/03635465241252435 PMID 39755947
  18. UK legislation. Human Medicines Regulations 2012, regulation 2; regulation 46; Regulation (EU) 2015/2283, Article 6.

Notice. This article is published by Free Muscle, which sells the research compounds discussed. Research compounds sold by Free Muscle are supplied for laboratory research use only and are not for human consumption. They are not authorised as medicines by the MHRA, EMA or FDA, are not food supplements, and are sold only to adults aged 18 or over. Nothing on this page is medical or dosing advice. This is general information, not legal advice.

Related guides