YK-11 10mg capsules, 60 per bottle
Structurally a steroid, not a true SARM. Sometimes described as a myostatin-pathway agent. Not authorised for human consumption in the UK or EU. Supplied for laboratory research use only. Read the evidence section below before you decide.
£0.83 per capsule · £0.083 per mg
WHAT IS
ACTUALLY KNOWN
We would rather you bought with your eyes open than not at all. Here is the state of the evidence, including the parts that do not help us.
What it is
This is a steroidal compound often grouped with SARMs. Structurally a steroid, not a true SARM. Sometimes described as a myostatin-pathway agent.
State of the evidence
The myostatin description rests largely on a single cell-culture study. There is no human data.
Known risks
A steroidal structure means androgenic and liver effects cannot be ruled out.
Regulatory status
Not authorised for human consumption in the UK or EU.
Status in sport
Prohibited in sport by WADA.
What we verify
Identity and purity, per batch, by a laboratory we do not own. We verify what is in the capsule, nothing about what it does.
SPEC SHEET
What is in the bottle, and what is on the certificate.
YK-11
10mg per capsule, as stated on the certificate of analysis for the batch.
Bottle contents
Each bottle contains 60 capsules.
Research use only
We do not publish a human dosing schedule for this compound.
Independently assayed
Each batch is assayed by Janoshik Analytical, an independent laboratory. The Certificate of Analysis for your batch is available on request.
This product is supplied for laboratory research use only. We do not provide dosing instructions, cycle lengths or post-cycle protocols for human use.
YK-11
Tax included · assayed per batch · £0.83 per capsule · £0.083 per mg
Multi-buy: buy more, pay less for each.
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WHAT WE CAN
PROVE
We don't have customer reviews to show you yet, and we're not going to invent any. Here is what we can actually put in front of you instead.
Assayed by a lab we don't own
Batches go to Janoshik Analytical, an independent testing laboratory. We don't choose the result.
Tested per batch, not per year
A certificate from a batch made two years ago says nothing about the pack in your hand.
Batch number on the pack
Email it to us with the product name and we'll send the Certificate of Analysis for that batch.
QUESTIONS, ANSWERED
Structurally a steroid, not a true SARM. Sometimes described as a myostatin-pathway agent. The myostatin description rests largely on a single cell-culture study. There is no human data.
This product is supplied for laboratory research use only. We do not provide dosing instructions, cycle lengths or post-cycle protocols for human use.
We do not give post-cycle therapy advice. This is a question for a qualified clinician, not for a shop.
Not strictly. It has a steroidal backbone, which is why grouping it with selective androgen receptor modulators is misleading. We would rather describe it accurately than conveniently.
Yes. Identity and purity, per batch, by Janoshik Analytical. Email us the batch number from your pack and we will send that batch's Certificate of Analysis. You do not need to have bought anything to ask.
Whoever you buy from, check five things: a batch number printed on the bottle, a certificate of analysis for that batch from a named laboratory, the strength per capsule stated by the seller, tracked delivery and a written returns policy. Free Muscle sells YK-11 as 10 mg capsules, 60 per bottle, for laboratory research use only, not for human consumption, to adults aged 18 or over, in our YK-11 collection. Every Free Muscle-brand batch is assayed by Janoshik Analytical, and we send the certificate for your batch on request.
YK-11 has no MHRA marketing authorisation, has never been licensed as a medicine anywhere and is not an authorised food supplement or novel food ingredient. It is not named in Schedule 2 to the Misuse of Drugs Act 1971; because it has a steroidal structure, and Part III also controls some steroids by a structural definition, we make no statement on whether that definition covers it. The 2026 WADA Prohibited List names it under section S1.2 (other anabolic agents), prohibited at all times. Free Muscle supplies it for laboratory research use only, not for human consumption, to adults aged 18 or over. This is general information, not legal advice.
Orders placed before 2pm UK time, Monday to Friday, are processed the same working day. UK delivery is free and tracked on every order, with no minimum spend, and usually takes 2–3 working days after dispatch; faster tracked UK delivery costs £6 and usually takes 1–2 working days after dispatch. Delivery to Romania and the rest of the EU uses our paid tracked international service and usually takes 3–7 working days after dispatch, and the rest of the world usually 5–14 working days. Details are on our shipping page.
Yes. Unopened items can be returned within 30 days; see our 30-day guarantee.
Adults aged 18 or over. YK-11 is supplied for laboratory research use only and is not for human consumption: we do not sell it as a medicine or as a food supplement, and we do not give dosing or usage advice.
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.
COMPOUND MONOGRAPH
Last reviewed: 16 October 2026 · sources and prices checked by Free Muscle.
Key facts
| What it is | A synthetic compound with a steroidal backbone, usually sold alongside SARMs; it has never been approved as a medicine. |
|---|---|
| Also known as | YK11 |
| CAS number | 1370003-76-1 |
| Molecular formula | C25H34O6 |
| Molar mass | 430.5 g/mol |
| This listing | 10 mg per capsule × 60 capsules (600 mg per bottle) |
| UK status | Not a licensed medicine in the UK (no MHRA marketing authorisation) and not an authorised food supplement or novel food ingredient. YK-11 is not named in Schedule 2 to the Misuse of Drugs Act 1971; it has a steroidal structure, and Part III also controls some steroids by a structural definition, on which we make no statement. This is general information, not legal advice. |
| Sport (WADA) | Prohibited at all times, in and out of competition: the 2026 WADA Prohibited List names YK-11 in section S1.2 (other anabolic agents), among SARMs. |
| What we verify | Every batch is assayed by Janoshik Analytical, an independent laboratory; the batch number is printed on the pack, and the certificate for your batch is sent by email on request. |
| Who can buy | Adults aged 18 or over, for laboratory research use only; not for human consumption. |
Where to buy YK-11 in the UK: what to check
Whichever seller you consider, check these five points:
- Stated strength and capsule count. Here: 10 mg per capsule, 60 capsules, 600 mg per bottle.
- A batch number on the pack. Here: printed on every bottle we ship.
- A certificate for that batch from a named independent laboratory. Here: Janoshik Analytical; we email the certificate for your batch on request.
- Tracked delivery in plain packaging and a written returns policy. Here: every order ships in plain packaging, UK delivery is free and tracked, EU delivery usually takes 3 to 7 working days after dispatch, and unopened items can be returned within 30 days.
- Sold for laboratory research only, to adults aged 18 or over. Here: no instructions for human use are given.
Our UK supplier checklist explains each point, and How we test sets out what a certificate does and does not prove.
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.
YK-11 in the UK: buying, legal status and what to check
Searches such as "yk11 buy uk" and "yk11 for sale uk" ask two things: can it be sold here, and how do you tell a sound listing from a doubtful one. YK-11 has no MHRA marketing authorisation, has never been licensed as a medicine anywhere, and is not an authorised food supplement or novel food ingredient, so it cannot lawfully be sold for human consumption. FreeMuscle, a business registered in Andorra with UK operations and dispatch in Scunthorpe, supplies it to adults aged 18 or over for laboratory research only. It is often listed among SARMs in UK searches, although chemically it is a steroid.
A listing worth trusting names the compound precisely (CAS 1370003-76-1), states the strength per capsule and the capsule count, prints a batch number on the pack and offers a certificate of analysis for that batch from a named laboratory. It ships in plain packaging with tracked delivery and publishes no human usage instructions. For this listing: 10 mg per capsule, 60 capsules (600 mg per bottle), a Janoshik Analytical certificate for every batch on request, and free tracked delivery in plain packaging. Orders placed before 2pm Monday to Friday are processed the same working day, and EU delivery takes 3 to 7 working days. See shipping, the guarantee and our UK supplier checklist.
Capsules compared with other forms
YK-11 is sold as capsules, as liquids in dropper bottles, as loose powder and, according to searches such as "yk11 injectable", in injectable form. None of these forms has been studied in people, so the comparison is about what can be measured and kept stable, not about effect. A capsule holds a weighed fill, fixed at manufacture, that an assay can check against the label. A liquid depends on how completely the compound stayed dissolved or suspended and on how accurately a dropper is read, and powder needs an analytical balance. Injectable products add questions of solvent and sterility that no published work on YK-11 addresses.
Stability favours a dry solid. YK-11 carries an orthoester-derived group on its D-ring that the Cologne doping-control group described as arguably labile (Piper 2018). Orthoesters as a class hydrolyse more readily in the presence of water and acid, so a solution exposes the compound to degradation for the life of the bottle in a way a sealed dry fill does not. Nor is YK-11 a peptide, despite the search "yk11 peptide": it is a small synthetic steroid, formula C25H34O6, so questions about peptides being digested do not apply to it.
YK-11 compared with RAD-140
RAD-140 (testolone) is the compound YK-11 is most often set against. RAD-140 is a non-steroidal SARM developed as a pharmaceutical candidate. YK-11 is a synthetic steroid on a 19-nor-pregnane skeleton, reported in cell assays as a partial agonist of the androgen receptor that activates it without inducing the N/C interaction seen with full androgens such as DHT (Kanno 2013).
| Point | YK-11 | RAD-140 |
|---|---|---|
| Structure | Steroidal, C25H34O6 | Non-steroidal, C20H16ClN5O2 |
| Published human data | None | A single phase 1 first-in-human study (22 patients), plus micro-dose excretion studies in 30 men |
| UK status | Not a licensed medicine; research use only | Not a licensed medicine; research use only |
| WADA class | S1.2, named in the 2026 list | S1.2, named in the 2026 list as RAD140 |
The evidence gap is the main difference. RAD-140 has one published first-in-human study, in 22 heavily pretreated postmenopausal women with ER-positive, HER2-negative metastatic breast cancer; the most frequent adverse events were raised liver enzymes (AST in 59.1% and ALT in 45.5% of patients), and grade 3 or 4 adverse events occurred in 72.7% (LoRusso 2022). No human trial of YK-11 has been published, so nothing comparable exists for it. The RAD-140 range is at /collections/rad-140.
Reading the certificate of analysis for this product
Each batch certificate from Janoshik Analytical has five fields worth reading. Identity confirms the material is YK-11, usually by HPLC retention time against a reference standard and by mass spectrometry. The PubChem record (CID 119058028) gives formula C25H34O6, molecular weight 430.5, monoisotopic mass about 430.24 and InChIKey KCQHQCDHFVGNMK-PQUNLUOYSA-N; a mass-spectrometry result should be consistent with these. It also specifies several stereocentres and an E-configured double bond, which a purity percentage alone cannot confirm. Purity is the main peak as a share of the total; the balance is related substances, residual solvent or degradation products. Content or assay is the amount found per capsule, the figure to set against the 10 mg on the label. The batch number must match the bottle exactly, and the test date shows how old the result is.
For this product a missing field has a simple meaning. Every Free Muscle batch is assayed, so a document without a batch number, test date or laboratory name is not the certificate for your bottle; ask us for the right one by emailing the batch number and product name through the contact page. Our guides to reading a certificate of analysis and Janoshik Analytical, and the lab tests page, go further.
Detection, sport and testing
YK-11 falls under S1, anabolic agents, on the WADA Prohibited List, and the 2026 edition names it in S1.2, other anabolic agents, among the examples of SARMs. It is prohibited at all times, in and out of competition, and S1 substances are non-Specified, which limits flexibility when sanctions are decided. UK Anti-Doping applies the same list.
Doping-control laboratories can find it. In an elimination study with deuterium-labelled YK-11, the Cologne laboratory identified fourteen urinary metabolites and no intact YK-11 in urine; unconjugated metabolites disappeared within 24 hours, glucuronidated and sulfated metabolites were traceable for more than 48 hours, and two glucuronides were added to the routine screening method for anabolic agents (Piper 2018). On "yk11 half life": no human pharmacokinetic study has been published, so no half-life is established, and the 48-hour figure is one study's observation rather than a detection window. In 2024 the UCLA Olympic Analytical Laboratory published the detection of YK-11 in a doping control sample (Sobolevsky 2024). YK-11 is detectable; the full window has not been established.
Storage, stability and handling
Keep the capsules in the original sealed bottle, somewhere cool and dry, away from direct light and heat. Moisture is the practical risk for a compound with a hydrolysable orthoester-derived group, so avoid bathrooms, kitchens and fridges, where condensation forms when a cold bottle is opened in warm air, and leave any desiccant sachet in place. Do not decant capsules into unlabelled containers: the batch number on the label is what links the material to its certificate. If capsules look discoloured, sticky or clumped, note the batch number and contact us. Keep out of reach of children and pets, and follow ordinary laboratory practice: gloves, no food or drink in the work area, and disposal in line with local rules for research chemicals.
What the published research reports
The evidence on YK-11 is small and entirely preclinical: cell-culture work, a handful of rodent studies and doping-control chemistry.
- Muscle cells. In C2C12 mouse myoblasts, YK-11 induced the myogenic factors MyoD, Myf5 and myogenin more strongly than DHT and, unlike DHT, induced follistatin; an anti-follistatin antibody reversed the differentiation (Kanno 2013). This study is the usual source of the "myostatin inhibitor" label. It measured follistatin, a myostatin-binding protein, in a mouse cell line, not myostatin or muscle tissue in a living animal.
- Rat brain. Over five weeks in male Wistar rats, YK-11 increased markers of oxidative stress and impaired mitochondrial function in the hippocampus; swimming exercise prevented some mitochondrial changes but not the oxidative stress (Dahleh 2023). The authors called for further research on the safety of YK-11 and SARMs in humans. A second five-week rat study from the same group reported reduced BDNF/TrkB/CREB signalling, raised IL-1beta and IL-6, activation of cell-death pathways and impaired memory consolidation (Dahleh 2024).
- Mouse sepsis. In mice infected with gram-negative bacteria, myostatin and follistatin rose in muscle, and YK-11, which the authors described as a myostatin inhibitor, reduced inflammatory cytokines, organ-damage markers and deaths (Lee 2021). This was an infection model in mice, not evidence about muscle or health in people.
- Rat bone repair. YK-11 promoted bone-forming differentiation of bone-marrow stem cells and, applied at the site in a hydrogel, the repair of skull defects in rats; inhibiting the androgen receptor suppressed both effects (Wang 2025).
Cell and rodent results do not predict effects in humans. None of this is a claim about the product on this page.
Related compounds and reading
- Every YK-11 listing, including iMuscle YK-11
- RAD-140 (testolone) and Free Muscle RAD-140
- LGD-4033, ostarine and the full SARMs range
- YK-11: a steroidal compound sold as a SARM, what is actually known
- What are SARMs? The 2026 research guide
- Price per milligram: comparing SARMs and peptides
Glossary
- Androgen receptor: the nuclear receptor activated by testosterone and DHT, and the receptor YK-11 binds.
- Partial agonist: a ligand that activates a receptor but produces less than the maximal response of a full agonist.
- N/C interaction: contact between the amino- and carboxyl-terminal regions of the androgen receptor, induced by full androgens; YK-11 was reported not to induce it.
- SARM: selective androgen receptor modulator, usually a non-steroidal molecule; YK-11 carries the label despite being a steroid.
- Follistatin: a protein that binds and neutralises myostatin and related growth factors.
- Myostatin: a growth factor that limits skeletal muscle growth.
- Orthoester: a carbon atom bonded to three alkoxy groups, a group prone to hydrolysis.
- Glucuronide: a metabolite joined to glucuronic acid for excretion; glucuronidated and sulfated YK-11 metabolites stayed traceable longest in the Cologne study.
- HPLC and LC-MS: liquid chromatography, alone or coupled to mass spectrometry, used for purity and identity testing.
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.
References
- Kanno Y, et al. Selective androgen receptor modulator, YK11, regulates myogenic differentiation of C2C12 myoblasts by follistatin expression. Biol Pharm Bull. 2013;36(9):1460-1465. PMID: 23995658.
- Dahleh MMM, 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. PMID: 37468001.
- Piper T, et al. Studies on the in vivo metabolism of the SARM YK11: Identification and characterization of metabolites potentially useful for doping controls. Drug Test Anal. 2018;10(11-12):1646-1656. PMID: 30379415.
- LoRusso P, et al. A First-in-Human Phase 1 Study of a Novel Selective Androgen Receptor Modulator (SARM), RAD140, in ER+/HER2- Metastatic Breast Cancer. Clin Breast Cancer. 2022;22(1):67-77. PMID: 34565686.
- Lee SJ, et al. Myostatin inhibitor YK11 as a preventative health supplement for bacterial sepsis. Biochem Biophys Res Commun. 2021;543:1-7. PMID: 33588136.
- Dahleh MMM, et al. From gains to gaps? How Selective Androgen Receptor Modulator (SARM) YK11 impact hippocampal function: In silico, in vivo, and ex vivo perspectives. Chem Biol Interact. 2024;394:110971. PMID: 38521455.
- Sobolevsky T, et al. Detection of selective androgen receptor modulator YK-11 in a doping control sample. Drug Test Anal. 2024;16(6):655-660. PMID: 37946705.
- Wang R, et al. YK11 promotes osteogenic differentiation of BMSCs and repair of bone defects. J Mol Endocrinol. 2025;74(2):e240073. PMID: 39660819.
