At a glance · 10 Nov 2026
- Suppliers serving the UK
- 11 list YK-11; 10 with a listing on sale (16 listings confirmed in stock)
- Based in the UK or shipping in
- 10 of the 10 stores with YK-11 on sale are based in the UK; 0 ship in from abroad or do not say where they are based.
- Sizes on sale
- Suppliers on this page sell YK-11 in 5 mg vials. Some also sell packs of 50 to 100 vials, compared per mg of the whole pack rather than against single vials. Other forms on sale (liquid) are different products and are not compared per mg with vials. How prices are compared
- Price per mg
- Not enough validated single-vial prices to publish a range yet
- Test certificates
- Not yet collected by PepFinder for YK-11; check each supplier's site. How to read a COA
- Legal status in the UK
- Most research peptides are not controlled drugs in the UK, but selling or supplying an unlicensed medicine is an offence under the Human Medicines Regulations 2012; growth hormone and HCG are Class C controlled drugs. Full summary with sources
What YK-11 is
YK-11 is a synthetic steroid derivative, first described by researchers at Toho University in Japan, that acts as a partial agonist of the androgen receptor and raised follistatin expression in cultured mouse muscle cells. It is sold as a SARM, but structurally it is a steroid, and its entire evidence base is three cell-culture papers: there are no human trials and no animal efficacy trials. It has never been approved as a medicine anywhere, the FDA has warned consumers about SARM products, and WADA prohibits SARMs in sport at all times. Read the full YK-11 guide, with the published research and references.
Before you choose a YK-11 supplier
Price per mg is only half the comparison. Check that the supplier publishes a certificate of analysis for the batch it is selling, ideally from an independent laboratory, and that the certificate confirms identity as well as purity: our guide on how to read a COA shows what to look for. A price far below the rest of the list is more often a warning than a bargain; peptide prices explained sets out why.
For what YK-11 is and what published studies have found, see our YK-11 guide. Handling questions are covered in how to store peptides, and the peptide calculator converts a vial size and water volume into concentration and syringe units. Rules on buying and importing differ by country: read are peptides legal in the UK? and see all suppliers serving the UK.
Checking a YK-11 certificate of analysis
- The certificate names a laboratory you can find independently, and ideally one with no stake in the result.
- It carries a batch or lot number that matches the product page or the vial label, and a test date.
- It confirms identity by mass spectrometry, not only purity by HPLC. Purity alone does not show the vial contains YK-11.
- It includes the chromatogram and mass spectrum, not just a summary table.
- Where the laboratory offers online verification of its reports, the report number checks out.
Red flags
- No certificates at all, or certificates available only “on request”.
- The same certificate used for several products or several years of stock.
- Payment only by cryptocurrency or bank transfer, with a discount for paying that way.
- A price far below every other supplier on this page.
- No way to contact the store other than a web form.
- Vials labelled only with a code rather than the product name and strength.
How to spot a fake peptide supplier explains each of these in more detail, and third-party peptide testing covers what independent results can and cannot prove.
Vials, capsules and pre-mixed products
Most research peptides are sold as freeze-dried (lyophilised) powder in sealed vials, which is mixed with a diluent such as bacteriostatic water before use in the lab. Some suppliers also sell pre-mixed solutions, nasal sprays or capsules under the same name. These are different products with different stability and dosing, so compare price per mg only between the same form, and check which form a listing is before comparing it with the rest of the table.
How this list is built: suppliers appear because they list YK-11 on their own website, read by our catalogue checks; nobody pays to be included or to move up. Ranking is by PepFinder Score, with stores that have nothing on sale after those that do. Prices, sizes and stock are as each site listed them when checked and may have changed.
