iMuscle Ibutamoren MK-677 is supplied as 60 capsules stated at 10 mg each, a total of 600 mg of MK-677 per pack. MK-677, also called ibutamoren, L-163,191 or Nutrobal, is an oral growth hormone secretagogue with a genuine human trial record. iMuscle manufactures the product and Free Muscle stocks it through the Muscle Market range for laboratory research by adults aged 18 and over.
About MK-677
MK-677, or ibutamoren, is an orally active ghrelin mimetic developed by Merck under the code L-163,191, a synthetic small molecule rather than a peptide. It binds the GHS-R1a receptor in the hypothalamus and pituitary, prompting pulsatile growth hormone release and a sustained rise in IGF-1. PubChem lists the free base as CID 178024, CAS 159634-47-6, formula C27H36N4O5S, molecular weight 528.7.
What the published research reports
The human literature is real but limited. In 1996 Chapman and colleagues reported that daily oral MK-677 in 32 healthy elderly volunteers, randomised against placebo, increased growth hormone pulse amplitude and raised IGF-1. Sampling every 20 minutes for 24 hours showed higher pulses and higher troughs between them, with no change in the number of pulses. IGF-binding protein 3 and fasting glucose rose; cortisol did not change. The study lasted four weeks at most and measured hormones only.
Svensson and colleagues then randomised 24 otherwise healthy obese men aged 18 to 50 to MK-677 or placebo for eight weeks (Svensson et al., 1998). IGF-1 rose by about 40 per cent with MK-677, significantly more than with placebo, and fat-free mass increased, while total and visceral fat did not change significantly. Basal metabolic rate was higher at two weeks but not significantly at eight, and an oral glucose tolerance test showed impaired glucose handling at both points although fasting glucose was unchanged.
The longest trial followed 65 healthy adults aged 60 to 81 for up to two years, with its main end points at twelve months (Nass et al., 2008). Fat-free mass went up by an average of 1.1 kg on MK-677 and drifted down by 0.5 kg on placebo, but strength, physical function and abdominal visceral fat did not differ, and limb fat grew more. Increased appetite, oedema, muscle pain, reduced insulin sensitivity, a small rise in fasting glucose, higher cortisol and greater weight gain were recorded. The authors judged the study too small and too short to assess function.
Across the three trials, higher growth hormone and IGF-1 came with poorer glucose handling, and the one trial that measured strength and function found no change in either. MK-677 was never approved as a medicine. Nothing in these studies is a claim about this listing.
This listing
- Compound: MK-677 (Ibutamoren)
- Brand: iMuscle
- Form: capsules
- Pack size: 60 capsules
- Stated strength: 10 mg per capsule (manufacturer's label claim)
- Stated total per pack: 600 mg
- Intended use: laboratory research only, not for human consumption
- Sold to adults aged 18 and over
The strength is the manufacturer's label claim; only a batch certificate confirms it. Because a figure is printed, this pack can be set against other brands of MK-677 on total milligrams, as explained in price per milligram, provided each figure refers to the same form: free base or the heavier mesylate salt.
MK-677 in the UK: buying, legal status and what to check
UK searches for this compound ask three things: is it legal ("MK 677 UK legal"), where can it be bought ("MK677 UK supplier", "MK 677 UK buy") and can a seller be trusted ("MK677 UK review").
The legal position
MK-677 is not a licensed medicine in the UK: it has no MHRA marketing authorisation, is not an authorised food supplement, and cannot lawfully be sold for human consumption. It is not a controlled drug either, which is why the question gets contradictory answers online; the restriction concerns what it may be sold as. Free Muscle supplies it to adults aged 18 or over for laboratory research only. It is prohibited at all times under section S2 (peptide hormones, growth factors and related substances) of the WADA Prohibited List. Buyers are responsible for the rules that apply to them, including any anti-doping code. See MK-677 legal status in the UK for more detail.
What a careful UK listing shows, and how this one compares
| Check | Why it matters | This listing |
|---|---|---|
| Named manufacturer and a UK seller | Someone is answerable for contents and sale | Made by iMuscle; sold by FreeMuscle LTD, Scunthorpe |
| Stated strength and count | Without both there is no pack total to compare | 10 mg x 60 capsules = 600 mg (label claim) |
| Lot number and a certificate for that lot | A certificate proves nothing unless the numbers match | iMuscle COA shown only where the manufacturer supplies one for the batch we hold |
| Research-use terms | Directions for use mean a product is being sold for consumption | 18+ only; no quantities, timings or promised outcomes |
| Tracked, discreet delivery | A traceable parcel is a record of the sale | Free tracked UK delivery in plain packaging; orders before 2pm Monday to Friday processed the same working day; EU 3-7 working days |
| Written returns policy | Terms are known before payment | 30-day returns on unopened items |
The certificate row varies for a third-party brand, so ask us before ordering if a current iMuscle certificate matters to your work. Forum and review searches meet a different limit: user reports describe sellers and parcels, but what a lot contains is a laboratory question. Prices change and appear on the listing, not in this text; cost per milligram is the fair measure. Our UK supplier checklist applies the same tests to any shop.
Capsules compared with other forms
MK-677 is also sold as tablets and research liquids, and is sometimes called a "peptide", which it is not. Every MK-677 trial cited here gave it by mouth, as the molecule was designed to be absorbed from the gut; none used an injectable form. Swallowed peptides, by contrast, are largely broken down by digestive enzymes (see do oral peptides work), which is why the human ipamorelin study below used an intravenous infusion.
Among solid forms, the question is how closely each unit matches the label. A capsule's content is fixed when powder, usually blended with a filler, is filled into shells, so an uneven blend lets one capsule differ from the next while the pack average stays right. Licensed medicines are tested for this as content uniformity, unit by unit; a research certificate reporting one pooled figure shows only the average. Tablets fix their content the same way at pressing.
Liquids carry a concentration instead, so the amount in a measured volume depends on complete dissolution, on the measuring device and on solvent not evaporating after opening, and most compounds degrade faster in solution than dry. None of this implies that one form acts differently in the body; it concerns only what a label and a certificate can vouch for.
MK-677 compared with ipamorelin
"Ibutamoren vs ipamorelin" is the comparison most often searched for this compound. Both are GHS-R1a agonists that prompt the pituitary to release its own growth hormone; the human data show where they part.
| Point | MK-677 (this product) | Ipamorelin |
|---|---|---|
| Chemical type | Non-peptide small molecule, C27H36N4O5S, 528.7, CAS 159634-47-6 | Pentapeptide Aib-His-D-2-Nal-D-Phe-Lys-NH2, C38H49N9O5, 711.9, CAS 170851-70-4 |
| Route in human studies | By mouth | Intravenous infusion |
| Time course in people | 24-hour growth hormone and IGF-1 raised during weeks of daily use | One burst of growth hormone peaking at about 40 minutes; terminal half-life about two hours |
| Human research base | Randomised trials in older adults (up to two years) and obese men | A pharmacokinetic study in healthy men across five infusion rates |
| UK status | Unlicensed; research use only | Unlicensed; research use only |
| WADA | S2, prohibited at all times | S2, prohibited at all times |
The time course is the sharpest contrast. In the study by Gobburu and colleagues, healthy men received ipamorelin as a 15-minute intravenous infusion; growth hormone rose in a single episode peaking at around 40 minutes and then declined, and the peptide's terminal half-life was about two hours (Gobburu et al., 1999). The MK-677 trials instead recorded raised 24-hour growth hormone and sustained IGF-1 during daily oral use. Different designs, routes and populations mean these profiles cannot rank the two, and we know of no trial giving both to the same people.
A PubMed search returns no human study of ipamorelin taken by mouth, so its human pharmacology comes from infusion alone, whereas MK-677's comes from oral use. Our ipamorelin listing is on the ipamorelin collection page; see also the ipamorelin research guide and MK-677 vs ipamorelin vs HGH. None of this recommends either compound.
Reading the certificate of analysis for this product
iMuscle is a third-party brand, so any certificate of analysis (COA) for this product is the manufacturer's, not ours. A COA is shown only where iMuscle supplies one for the batch we hold; a generic document is not a substitute for a batch certificate. A real batch certificate carries the lot number printed on the pack, the test method (HPLC or LC-MS) and a purity figure. Free Muscle-brand compounds are assayed batch by batch at Janoshik Analytical; that programme does not cover iMuscle. Read an iMuscle certificate against this page:
- Identity. HPLC matches the sample's retention time to an ibutamoren reference standard; LC-MS adds a measured mass, about m/z 529.25 for protonated C27H36N4O5S.
- Purity, as a percentage. It grades the material, not the amount; a high figure is compatible with capsules holding well over or under 10 mg.
- Content per capsule. The line that tests the 10 mg claim; multiplied by 60, it gives the real pack total to set against 600 mg. It should say whether it is expressed as free base or mesylate.
- Batch number and test date. These tie the result to your pot and show its age.
For this brand, a missing certificate leaves 10 mg and 600 mg as iMuscle's claim only; purity without content supports identity but not strength; a batch number that differs from your pot means another production run. In each case contact us with the lot number. See how to read a COA and our lab tests page.
Detection, sport and testing
Ibutamoren is prohibited in and out of competition under section S2 of the WADA Prohibited List, named among the growth hormone secretagogues; in the UK the list is applied by UK Anti-Doping. Accredited laboratories screen urine for it and its metabolites, athletes have been sanctioned after positive findings, and strict liability makes an athlete responsible for whatever is in their sample. A research-use label on a product changes nothing in that respect.
A PubMed search for ibutamoren in urine returns metabolism work in horses and hormone studies in volunteers, but no human excretion study that sets a detection window, so the accurate answer is: detectable, window not established. Windows quoted online without a study behind them deserve no weight, and blood half-life is no guide, because laboratories also target metabolites. Anyone bound by an anti-doping code should treat any exposure to MK-677 as a likely adverse finding and check the current list, which WADA revises every year.
Storage, stability and handling
We found no published stability study of ibutamoren capsules, so no shelf life is given here. Any date iMuscle prints on the pack is the limit, and a certificate describes the batch only as it was when tested.
- On arrival. Check the seal and record the lot number and date of receipt; only unopened items can be returned within 30 days. On first opening, count the capsules and tell us the lot number if there are not 60.
- In storage. Keep the pack closed in its original container, cool, dry and away from light. Humidity softens, sticks or cracks capsule shells and speeds the breakdown of damp powder; leave any desiccant sachet in place.
- In use. Wear nitrile gloves, work away from food and drink, and never decant capsules or mix lots, because the lot number on the pack is the only link to its certificate.
- Throughout. Keep the product out of reach of children and pets, set aside discoloured, clumped or split capsules, and dispose of surplus as chemical waste, not in household bins or drains.
Glossary
- Ghrelin mimetic: a compound that activates the ghrelin receptor as the stomach hormone ghrelin itself does.
- GHS-R1a: the type 1a growth hormone secretagogue receptor; both compounds compared on this page are agonists at it.
- Pulse amplitude: the height of each burst of growth hormone; MK-677 raised it without adding bursts.
- IGF-1 and IGFBP-3: insulin-like growth factor 1, produced largely by the liver when growth hormone rises, and the protein that carries most of it in blood.
- Oral glucose tolerance test: a measure of how blood glucose responds to a standard glucose drink; it can reveal impairment while fasting glucose looks normal.
- Fat-free mass: everything in the body that is not fat, bone and body water included, so it is not a measure of muscle alone.
- Terminal half-life: the time for blood concentration to halve once a compound has distributed; about two hours for infused ipamorelin.
- Content uniformity: how closely individual units match the label claim, as opposed to the batch average.
- Retention time: how long a compound takes to pass through an HPLC column, the basis of an HPLC identity match.
- Mesylate: a methanesulfonate salt; ibutamoren mesylate is heavier than the free base, so equal milligrams hold unequal amounts of ibutamoren.
Related
- All brands of MK-677 (Ibutamoren), compared on strength, pack size and batch testing
- All iMuscle products
- Free Muscle's own MK-677: 10mg, 12.5mg and 25mg, each batch assayed by Janoshik Analytical
- Ipamorelin, the peptide compared above
- Background reading: the MK-677 research review and how MK-677 brands differ
- Delivery and returns
This product is supplied for laboratory research use only. It is not a medicine or a food supplement, has not been evaluated by the MHRA, EMA or FDA, and is not for human consumption. Sold to adults aged 18 and over. Nothing on this page is medical, dosing or usage advice.
References
- Chapman IM, et al. Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretogogue (MK-677) in healthy elderly subjects. J Clin Endocrinol Metab. 1996;81(12):4249-57. PMID: 8954023.
- 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.
- 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.
- Gobburu JV, et al. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res. 1999;16(9):1412-6. PMID: 10496658.
Frequently asked questions
Is MK-677 legal in the UK?
It is not a controlled drug in the UK, yet it holds no MHRA licence as a medicine and is not an authorised food supplement, so it may not be sold for human consumption. Free Muscle supplies this iMuscle pack for laboratory research only, and only to adults aged 18 and over. In sport, WADA prohibits it under section S2. More detail is on our MK-677 legal status page.
Is MK-677 a SARM?
No. MK-677 (ibutamoren) is a growth hormone secretagogue that acts as an agonist at the ghrelin receptor, prompting the pituitary to release growth hormone. It does not bind the androgen receptor. It is often sold alongside SARMs and grouped with them in shops, but the mechanism, the trial literature and the WADA category (S2 rather than S1) are all different.
Is MK-677 a peptide?
No, although it is often sold beside peptides and searched for as one. MK-677 is a synthetic non-peptide small molecule, formula C27H36N4O5S and molecular weight 528.7, designed to act at the same receptor as the growth hormone releasing peptides while remaining active by mouth. Peptides such as ipamorelin are chains of amino acids that digestive enzymes largely break down. Free Muscle sells MK-677 for laboratory research only, to adults aged 18 and over.
Is MK-677 a supplement?
No. In the UK MK-677 is not an authorised food supplement, and with no MHRA marketing authorisation it is not a licensed medicine either, so it cannot lawfully be sold for people to take under either heading. Listings elsewhere that call it a supplement do not change that. This iMuscle pack is sold as a research compound for laboratory use only, to adults aged 18 and over.
What is the difference between ibutamoren and ipamorelin?
Both activate the ghrelin receptor, GHS-R1a, and prompt the pituitary to release growth hormone. Ibutamoren (MK-677) is a non-peptide molecule studied by mouth, with growth hormone and IGF-1 raised during weeks of daily use in trials. Ipamorelin is a five-residue peptide; in its human study, given by intravenous infusion, it produced a single burst of growth hormone and had a half-life of about two hours. Neither is a licensed medicine, and WADA lists both under S2.
What side effects of MK-677 have been reported in research?
In the 2008 trial of 65 adults aged 60 to 81, the most frequent were increased appetite that eased within a few months, and transient mild leg swelling and muscle pain; fasting glucose rose, insulin sensitivity fell, cortisol increased and body weight rose more than on placebo. A 1998 trial in obese men found impaired glucose tolerance at two and eight weeks. These were findings in supervised study participants, not predictions and not claims about this pack.
What strength of MK-677 should I choose?
We give no advice on strength or quantity: MK-677 is sold for laboratory research, not for human use. The 10 mg per capsule and 600 mg per pack shown here are iMuscle's label details, listed so packs can be compared on total milligrams and checked against a batch certificate. How a compound behaves in people is a question for the published literature, not for a product page.
Do you publish MK-677 dosage, cycle, benefits or before-and-after information?
No. This pack is sold for laboratory research, not for human consumption, so the page carries no amounts, schedules, cycle lengths or combinations, and no promised benefits or results. A before-and-after photograph records neither what a capsule held nor what else changed between the two pictures, so it is not evidence about any product. What the controlled trials measured, adverse findings included, is summarised above for reference only.
How do I verify the batch of iMuscle MK-677 I receive?
Check that the lot number printed on your pack is the one on the certificate of analysis, then read the content line against 10 mg per capsule. An iMuscle COA is shown only where the manufacturer has supplied one for the batch we hold, so contact us to ask about current stock. A certificate with no batch number, or a different one, does not verify your pack.
Is MK-677 detectable in sports drug tests?
Yes. WADA lists ibutamoren under section S2 of its Prohibited List, banned in and out of competition, and accredited laboratories screen urine for the compound and its metabolites. Athletes have been sanctioned for it. No verified human study sets a detection window, so anyone subject to anti-doping testing should treat MK-677 as a substance that will produce a positive result.
Related research and listings
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- Research guides: What Is Janoshik Analytical? Third-Party Testing Explained
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Supplied for laboratory and research use. Not for human consumption. Not an approved medicine, and nothing above is dosing advice. You must be 18 or over to order.