Testolone + YK-11 + Ibutamoren stack

iMuscle Testolone + YK-11 + Ibutamoren stack is a 60-capsule combined listing from iMuscle, labelled as containing three research compounds: YK-11, Testolone (RAD-140) and Ibutamoren (MK-677). The manufacturer does not state the amount of each compound per capsule on the label. It is supplied through the Muscle Market range for laboratory research only, is not for human consumption, and is sold to adults aged 18 and over. Each compound is covered in turn below.

This listing

• Manufacturer: iMuscle
• Compounds named on the label: YK-11, Testolone (RAD-140) and Ibutamoren (MK-677)
• Form: capsules
• Pack size: 60 capsules
• Strength: not stated by the manufacturer for any of the three compounds, so no per-capsule or per-pack figure is given
• Batch certificate of analysis: shown where iMuscle supplies one for the batch we hold
• Sold to adults aged 18 and over, for laboratory research only

iMuscle also sells each compound on its own with a stated strength: iMuscle YK-11, iMuscle Testolone RAD-140 and iMuscle Ibutamoren MK-677 are each labelled 10 mg per capsule, 60 capsules.

The three compounds in this pack

YK-11

YK-11 is a synthetic steroidal compound, a 19-nortestosterone derivative carrying a methoxyethylidene group, that is marketed as a SARM. It was first described by Kanno and colleagues at Toho University in Japan (PubChem CID 119058028, CAS 1370003-76-1, C25H34O6).

In a 2011 cell-culture study using a reporter-gene assay, YK-11 acted as a partial agonist of the androgen receptor and activated it without the receptor's N/C-terminal interaction that dihydrotestosterone induces (Kanno 2011). A 2013 study in mouse C2C12 myoblast cells reported that YK-11 increased follistatin expression and promoted myogenic differentiation through the androgen receptor, the origin of the myostatin-inhibitor description (Kanno 2013). Those are the founding primary studies; there are no human trials or toxicology data, and later work has been limited to a few rodent studies and doping-control metabolism research. It has never been approved as a medicine.

RAD-140 (Testolone)

RAD-140, also listed as testolone and vosilasarm, is a non-steroidal selective androgen receptor modulator designed by Radius Health (PubChem CID 44200882, CAS 1182367-47-0, C20H16ClN5O2). Its human data come from a single clinical trial. A first-in-human phase 1 study enrolled 22 postmenopausal women with oestrogen receptor-positive, HER2-negative metastatic breast cancer and gave RAD-140 by mouth (LoRusso 2022). The most frequent adverse events were raised AST in 59.1 per cent of participants, raised ALT in 45.5 per cent and raised bilirubin in 27.3 per cent, and 16 of the 22 had a grade 3 or 4 adverse event. The measured half-life was 44.7 hours. The trial assessed tolerability and tumour response, not muscle or strength, and RAD-140 has not been approved as a medicine anywhere.

MK-677 (Ibutamoren)

MK-677, or ibutamoren, is a non-peptide growth hormone secretagogue developed by Merck under the code L-163,191 (PubChem CID 178024, CAS 159634-47-6, C27H36N4O5S). It mimics ghrelin at the GHS-R1a receptor, prompting the pituitary to release growth hormone, and it raises IGF-1. Randomised trials in older adults and in obese men recorded higher growth hormone and IGF-1 together with poorer glucose handling, and in the older adults increased appetite and mild oedema (Nass 2008; Svensson 1998); those trials are summarised in MK-677 (ibutamoren): what the research says. It was never approved as a medicine.

Each compound was studied on its own. No published study has examined YK-11, RAD-140 and MK-677 together, in cells, animals or people. We do not advise on combining compounds; the listing is described as the manufacturer presents it. Nothing above is a claim about this product.

YK-11, RAD-140 and MK-677 in the UK: buying, legal status and what to check

None of the three compounds is a licensed medicine in the UK. None holds an MHRA marketing authorisation, none is an authorised food supplement, and none may lawfully be sold for human consumption. Free Muscle supplies this pack to adults aged 18 and over for laboratory research only.

The three do not sit in identical positions. YK-11 is a steroid, and because anabolic steroids are Class C controlled drugs in the UK its status is less clear-cut than that of RAD-140, a non-steroidal SARM with no steroid backbone. MK-677 acts on the growth hormone axis; its UK position is set out on our MK-677 legal status page. All three are prohibited in sport. Buyers are responsible for the rules that apply to them, and our SARMs research guide covers the wider legal picture.

What to check before buying a multi-compound pack

• Every compound named precisely, with a separate stated amount per capsule for each. A list of names alone does not say how much of anything is present.
• A printed lot number that ties the pack to a named laboratory's certificate.
• A certificate that identifies and quantifies each compound, not only the one in the product title.
• A named UK company, an 18+ restriction, plain packaging and tracked delivery.
• No instructions for human use, no stacking advice and no promises of outcomes.

How this listing measures up

iMuscle does not state per-capsule amounts, so this listing fails the first check, and we do not fill the gap with an estimate. A certificate is shown only where iMuscle supplies one for the batch we hold. Orders ship from FreeMuscle LTD in Scunthorpe with free tracked UK delivery in plain packaging, orders placed before 2pm Monday to Friday are processed the same working day, EU delivery takes 3 to 7 working days, and unopened items can be returned within 30 days (delivery, returns). Our UK supplier checklist explains each test.

Capsules compared with other forms

YK-11, RAD-140 and MK-677 are each sold separately as capsules, liquids and powder. No study has compared these forms for any of the three, so the points here concern what can be measured and kept stable, not effect. This pack is a single capsule said to hold all three.

Putting three compounds in one fill changes the measurement problem. In a blend, the amount of each compound depends on how evenly the powders were mixed before filling, and a minor component that is poorly mixed can vary from capsule to capsule even when the total fill weight is consistent. Only a content assay of finished capsules, reporting each compound separately, shows the actual ratio.

The chemistry points the same way. All three are small molecules rather than peptides, so the digestion argument made about peptides taken by mouth, discussed in Do oral peptides actually work?, does not apply to them. YK-11 carries an orthoester-derived group that its main metabolism study called arguably labile (Piper 2018), which makes a water-free fill easier to keep stable than a solution. MK-677 is often supplied as its mesylate salt, which weighs more than the free base, so a label amount should say which form it refers to. None of this is a claim about what a capsule does.

YK-11 compared with RAD-140 and MK-677, and where RAD-150 fits

A common question is how the three compounds differ, and how RAD-140 relates to RAD-150. The table uses only points that published sources support.

Point	YK-11	RAD-140	MK-677
Chemical family	Steroidal, 19-nor skeleton	Non-steroidal SARM	Non-peptide ghrelin mimetic
Main target	Androgen receptor, partial agonist in cell assays	Androgen receptor	Ghrelin receptor (GHS-R1a)
Formula and molecular weight	C25H34O6, 430.5	C20H16ClN5O2, 393.8	C27H36N4O5S, 528.7
Developed by	Academic group, Toho University	Radius Health	Merck, as L-163,191
Published human data	None	One phase 1 trial, 22 women with metastatic breast cancer	Randomised trials in older adults and obese men
Adverse findings in people	Not studied	Raised liver enzymes and bilirubin	Poorer glucose handling, appetite, oedema
WADA section	S1, anabolic agents	S1, anabolic agents	S2, growth hormone secretagogues

Two of the three share a target. YK-11 and RAD-140 both act at the androgen receptor, though they come from unrelated chemical families, while MK-677 works on a separate system, the growth hormone and IGF-1 axis. On human evidence, MK-677 has the most trial data, RAD-140 a single oncology study, and YK-11 none. Nothing here ranks one above another for any purpose.

RAD-150, also sold as TLB-150, is not in this pack. PubChem records it as the benzoate ester of RAD-140; it appears in a Radius Health patent but has no peer-reviewed study, so claims that it acts for longer are inference. It is stocked separately on the RAD-150 collection page, and RAD-140 vs RAD-150 (TLB-150) sets out the chemistry. For MK-677 the most searched comparison is with ipamorelin, a peptide acting at the same ghrelin receptor; see the ipamorelin collection and MK-677 vs ipamorelin vs somatropin.

Reading the certificate of analysis for this product

iMuscle is a third-party brand in the Muscle Market range, so any certificate for this pack is the manufacturer's, not ours. We show one only where iMuscle supplies it for the specific batch we hold, and a generic PDF with no batch number is not a batch certificate, so we do not present one as such. Janoshik Analytical testing of every batch applies to Free Muscle-brand products only, not to iMuscle. A three-compound certificate has more to prove; check these fields.

• Batch number: the same number as the one printed on your pack.
• Identity of each compound: a method such as HPLC against reference standards or LC-MS, with a separate result for YK-11 (C25H34O6, 430.5), RAD-140 (C20H16ClN5O2, 393.8) and MK-677 (C27H36N4O5S, 528.7 as the free base). A certificate that confirms only one of them says nothing about the other two.
• Content per capsule for each compound: because iMuscle states no strengths, these figures would be the only statement of how much of each is present.
• Purity: in a blend a single percentage is ambiguous, because three main peaks are expected. Look for each compound reported separately, with any unidentified peaks listed on their own.
• Test date and laboratory: a named lab and date allow the result to be confirmed at source.

For this listing a missing field has a specific meaning. With no certificate for the batch in stock, nothing independent confirms which compounds are present or in what amounts. With identity results but no content figures, the certificate confirms presence, not quantity. Email us through the contact page with the product name and batch number and we will send what we hold, or say plainly that there is none. See lab tests and how to read a certificate of analysis.

Detection, sport and testing

Every compound in this pack is prohibited at all times, in and out of competition, on the WADA Prohibited List, which UK Anti-Doping applies in the UK. YK-11 and RAD-140 fall under section S1, anabolic agents, where RAD-140 is named; MK-677 falls under section S2 as a growth hormone secretagogue. Under strict liability an athlete answers for any prohibited substance found in their sample, whatever a label says.

For YK-11 there is direct evidence. The Cologne anti-doping laboratory followed deuterium-labelled YK-11 through urine. The parent compound never appeared, but fourteen metabolites did. Free metabolites were gone by 24 hours, whereas forms bound to glucuronic acid or sulfate remained measurable past 48 hours, and two of them were built into the laboratory's screen for anabolic agents (Piper 2018). That is one study, not a detection window. RAD-140 and MK-677 are screened for by accredited laboratories as well; this page cites no study that sets a window for either, so the accurate answer for both is detectable, window not established. A blood half-life is no guide to detection, since laboratories also target metabolites.

Storage, stability and handling

No stability study has been published for YK-11, RAD-140 or MK-677 capsules, singly or combined, so no shelf life is given here beyond any date iMuscle prints on the pack. A blend is only as stable as its least stable component. The ester and orthoester-derived groups of YK-11 can be split by water, which makes moisture the main avoidable risk for the whole capsule.

• Store the sealed container cool, dry and out of direct light.
• Replace the lid straight after opening and leave any desiccant sachet in place.
• Keep capsules in their own labelled pot; once moved or mixed, they lose their link to any certificate.
• Note the date received alongside the batch number.
• Set aside soft, sticky or discoloured capsules and contact us with the batch number.
• Wear gloves, work away from food, drink, children and pets, and treat any surplus as chemical waste.

Only unopened items can be returned within 30 days.

Glossary

• Androgen receptor: the receptor inside cells that testosterone switches on; YK-11 and RAD-140 both bind it, from different chemical starting points.
• SARM: selective androgen receptor modulator; RAD-140 is one, while YK-11 is a steroid sold under the same label.
• Growth hormone secretagogue: MK-677's class, meaning any substance that triggers growth hormone release from the pituitary gland.
• GHS-R1a: the receptor for the hunger hormone ghrelin, which MK-677 mimics.
• IGF-1: insulin-like growth factor 1, the hormone the liver releases when growth hormone rises; MK-677 trials tracked it.
• AST and ALT: liver enzymes whose blood levels rise when liver cells are damaged; the most frequent adverse findings in the RAD-140 phase 1 trial.
• Phase 1 trial: first-in-human testing that asks how well a compound is tolerated and how the body handles it, not whether it works.
• Mesylate salt: a form of a compound paired with methanesulfonic acid that weighs more than the free base.
• Blend uniformity: how evenly several powders are mixed before capsule filling, which decides whether each capsule holds the same ratio of compounds.
• Strict liability: the rule under which a prohibited substance in an athlete's sample counts against them whether or not they knew it was there.

Related

• All brands of YK-11 we stock, compared
• RAD-140 (Testolone) collection and MK-677 (Ibutamoren) collection
• All iMuscle products and Muscle Market bundles
• YK-11: a steroidal compound sold as a SARM, what is actually known
• RAD-140 (Testolone): what the research says
• Batch testing and certificates of analysis
• Delivery and returns

This product is supplied for laboratory research use only. It has not been evaluated by the MHRA, EMA or FDA. It is not a medicine, not a food supplement and not for human consumption. Sold only to adults aged 18 and over. Nothing on this page is medical, dosing or usage advice, and descriptions of published studies are not claims about this product.

References

1. Kanno Y, 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. PMID: 21372378.
2. Kanno Y, et al. Selective androgen receptor modulator, YK11, regulates myogenic differentiation of C2C12 myoblasts by follistatin expression. Biol Pharm Bull. 2013;36(9):1460-5. PMID: 23995658.
3. 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):1646-56. PMID: 30379415.
4. 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.
5. Nass R, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med. 2008;149(9):601-11. PMID: 18981485.
6. Svensson J, et al. Two-month treatment of obese subjects with the oral growth hormone (GH) secretagogue MK-677 increases GH secretion, fat-free mass, and energy expenditure. J Clin Endocrinol Metab. 1998;83(2):362-9. PMID: 9467542.