MK-677 (Ibutamoren)
7 products from 4 brands · free UK delivery · EU 3–7 days
Every MK-677 (Ibutamoren) listing compared
Strength and pack size as stated by each manufacturer. Total milligrams = strength per capsule multiplied by capsules per pack. Price per milligram is calculated from the current price. A dash means the manufacturer does not state that figure.
| Brand | Listing | Strength | Pack | Total | Price | Per mg | Availability |
|---|---|---|---|---|---|---|---|
| FreeMuscle | MK-677 Ibutamoren — 25mg · 60 Capsules | 25mg | 60 capsules | 1500mg | £69.99 | £0.047 | In stock |
| FreeMuscle | MK-777 (Acetamoren) — Bioreactive Series | – | – | – | £69.99 | – | In stock |
| FreeMuscle | MK-677 Ibutamoren — 10mg · 60 Capsules | 10mg | 60 capsules | 600mg | £49.99 | £0.083 | In stock |
| FreeMuscle | MK-677 Ibutamoren — 12.5mg · 60 Capsules | 12.5mg | 60 capsules | 750mg | £44.99 | £0.060 | In stock |
| Yakka Strength | MK-677 | – | 60 capsules | – | £64.99 | – | In stock |
| Thoroughbred Labs | MK-677 | – | 60 capsules | – | £44.99 | – | In stock |
| iMuscle | Ibutamoren MK-677 — 60 caps, 10mg | 10mg | 60 capsules | 600mg | £62.99 | £0.105 | In stock |
MK-677, also known as ibutamoren, ibutamoren mesylate, MK-0677, L-163,191 and Nutrobal, is a non-peptide growth hormone secretagogue: an orally active small molecule that acts as an agonist at the ghrelin receptor, GHS-R1a. This page lists every brand of MK-677 stocked at Free Muscle, our own Janoshik batch-tested capsules alongside iMuscle, Yakka Strength and Thoroughbred Labs, compared on strength per capsule, pack size and batch testing. Everything here is supplied for laboratory research only, to adults aged 18 or over.
What is MK-677?
MK-677 belongs to the growth hormone secretagogue class. It was developed at Merck in the 1990s as an orally available, non-peptide mimic of the growth hormone releasing peptides such as GHRP-6, which are only active by injection. It binds and activates the growth hormone secretagogue receptor (GHS-R1a) in the pituitary and hypothalamus, the same receptor that the stomach hormone ghrelin acts on. In trial participants, this amplified the pulsatile release of growth hormone and raised circulating insulin-like growth factor 1 (IGF-1) levels.
It is worth being precise about what MK-677 is not. It is not a SARM, not an anabolic steroid, not a peptide and it contains no growth hormone. It is unusual among research compounds sold in the UK in having a substantial published human trial record, including studies in older adults, obese men, patients recovering from hip fracture and patients with Alzheimer disease. Despite that record, it was never approved as a medicine anywhere in the world, and clinical development was discontinued.
What the published research reports
In a two-year randomised, placebo-controlled trial in 65 healthy adults aged 60 to 81 (Nass et al., 2008), MK-677 raised growth hormone and IGF-1 into the range seen in young adults. Fat-free mass rose by about 1.1 kg in the MK-677 group against a fall of 0.5 kg on placebo, and body weight rose by 2.7 kg against 0.8 kg. Abdominal visceral fat and total fat mass did not change, but limb fat increased more in the treated group. Fasting glucose rose, insulin sensitivity fell, cortisol increased, and the most frequent side effects were increased appetite, transient lower-limb oedema and muscle pain. The extra fat-free mass did not translate into any change in strength or function.
In an eight-week trial in 24 obese men (Svensson et al., 1998), serum IGF-1 rose by roughly 40 per cent and fat-free mass increased, while total and visceral fat were unchanged. Basal metabolic rate rose at two weeks but not at eight, and an oral glucose tolerance test showed impaired glucose handling at both time points.
A phase IIb study in 123 elderly patients recovering from hip fracture (Adunsky et al., 2011) found that IGF-1 rose but most functional measures did not improve. The trial was terminated early because of a safety signal of congestive heart failure in a small number of patients, and the authors concluded that the compound had an unfavourable safety profile in that population.
None of these findings is a claim about the products listed on this page. They describe what was measured in specific trial populations under medical supervision, and they include the adverse findings for a reason.
Brands of MK-677 we stock
- Free Muscle MK-677 Ibutamoren: our own brand, capsules, 60 per bottle, in three strengths: 10mg, 12.5mg and 25mg. Every batch is assayed for identity and purity by Janoshik Analytical, with the Certificate of Analysis sent on request. The three strengths have their own page at Free Muscle MK-677 Ibutamoren.
- iMuscle Ibutamoren MK-677: 10mg per capsule, 60 capsules, 600mg total per pack. A COA is shown where iMuscle supplies one for the batch we hold.
- Yakka Strength MK-677: 60 capsules. The strength per capsule is stated on the product listing where the manufacturer declares it. A COA is shown where Yakka Strength supplies one for the batch we hold.
- Thoroughbred Labs MK-677: 60 capsules. Check the listing for the declared strength. A COA is shown where Thoroughbred Labs supplies one for the batch we hold.
- MK-777 (Acetamoren) Bioreactive Series: a Free Muscle product designation from our Bioreactive Series, 60 capsules, Janoshik batch-tested. MK-777 is not a name found in the published pharmacological literature, so it is compared on its own page at MK-777 rather than treated as an MK-677 equivalent.
- Research Bundle: MK-677 + RAD-140 + YK-11 (not listed at the moment; see other bundles and stacks): a Free Muscle bundle of three separate research compounds in one parcel. Each item in it is batch-tested individually.
How to compare them
Two bottles of 60 capsules can contain very different quantities of compound. Multiply the strength per capsule by the number of capsules to get total milligrams per pack: 10mg x 60 is 600mg, 12.5mg x 60 is 750mg, 25mg x 60 is 1,500mg. Divide the price on the listing by that total to get a cost per milligram, which is the only like-for-like comparison between brands. Then check whether a batch certificate exists for the exact batch on the label, because an untested 25mg capsule is not worth more than a tested 10mg one. Our article MK-677 by brand walks through the same arithmetic.
Batch testing and certificates of analysis
A Certificate of Analysis (COA) is a laboratory report on one specific batch. For MK-677 it should show the identity of the compound (usually by HPLC or mass spectrometry against a reference standard), the measured purity as a percentage, the batch number, the date of testing and the name of the laboratory. Every Free Muscle brand batch is assayed by Janoshik Analytical, an independent laboratory; email us with the batch number printed on your label and we send the certificate for that batch. For iMuscle, Yakka Strength and Thoroughbred Labs, a COA is shown on the listing only where the manufacturer supplies one for the batch we hold. A generic PDF with no batch number, or a certificate for a batch that is not the one in your hand, is marketing rather than evidence. See how we test and how to read a COA.
Legal status in the UK
MK-677 is not a licensed medicine in the UK and has no marketing authorisation from the MHRA. It is not an authorised food supplement or novel food, and it cannot be sold for human consumption. Free Muscle supplies it as a research compound for laboratory use only, to customers aged 18 or over. Growth hormone secretagogues, including ibutamoren, are prohibited at all times under section S2 of the WADA Prohibited List, so it is not compatible with drug-tested sport. Full detail is on our MK-677 legal status in the UK page.
Storage and handling
Keep capsules in the original sealed container, in a cool, dry place away from direct light and heat. Reseal after opening and do not decant into unlabelled containers. Keep out of the reach of children and pets. Handle in line with normal laboratory good practice, record the batch number for any work you carry out, and dispose of unwanted material responsibly.
Delivery and returns
Free Muscle is a UK company (FreeMuscle LTD, Scunthorpe). Every order ships with free tracked UK delivery in plain packaging, and orders placed before 2pm Monday to Friday are processed the same working day. EU delivery takes 3 to 7 working days. Unopened items can be returned within 30 days. See delivery and our 30-day guarantee.
Related reading
- MK-677 (Ibutamoren): What the Research Says
- MK-677 by brand: what actually differs when the molecule is the same
- Price per milligram: the only honest way to compare SARMs and peptides
- What Is Janoshik Analytical? Third-Party Testing Explained
- What Are SARMs? The 2026 Research Guide
All MK-677 products on this page are sold for laboratory research use only. They are not licensed medicines, have not been evaluated by the MHRA, EMA or FDA, and are not for human consumption. Customers must be 18 or over. Nothing on this page is medical advice or dosing guidance.
Research guides
Frequently asked questions
Is MK-677 legal in the UK?
MK-677 is not a controlled substance in the UK, but it is not a licensed medicine and not an authorised food supplement, so it cannot be sold for human consumption. Free Muscle sells it as a research compound for laboratory use to adults aged 18 or over. It is prohibited in sport under the WADA list. Our MK-677 legal status page covers the detail.
Is MK-677 a SARM?
No. SARMs act at the androgen receptor. MK-677 is a growth hormone secretagogue that acts at the ghrelin receptor (GHS-R1a) and has no direct androgenic activity. It is often sold alongside SARMs because it comes from the same suppliers, but it is a different class of compound with a different receptor and a different research literature.
What is the difference between MK-677 and MK-777?
MK-677 (ibutamoren) is a compound with published human trials. MK-777 (Acetamoren) is Free Muscle's own product designation for a Bioreactive Series capsule; you will not find it in the pharmacological literature under that name, and there are no trials under it. We keep the two on separate pages so nobody mistakes one for the other.
Which strength of MK-677 should I choose?
We do not advise on strength. MK-677 is sold for laboratory research only, and any recommendation would amount to dosing guidance for human use, which we do not give. The strengths listed simply reflect the quantity of compound per capsule. Compare total milligrams per pack and the batch certificate, and choose according to your research requirements.
How do I verify the batch of MK-677 I have bought?
Find the batch number on the label. For Free Muscle brand, email it to us and we send the Janoshik Analytical certificate for that batch, showing identity and purity. For iMuscle, Yakka Strength and Thoroughbred Labs, the manufacturer's certificate is shown on the listing where one exists for the batch we hold. Always match the batch number on the certificate to the one on the bottle.
Will MK-677 show up in a sports drug test?
Ibutamoren is named on the WADA Prohibited List as a growth hormone secretagogue and is banned at all times, in and out of competition. Accredited laboratories have detection methods for it and its metabolites. Anyone subject to anti-doping testing should treat it as a prohibited substance.
How is MK-677 shipped and can I return it?
Every order ships with free tracked UK delivery in plain packaging, with no reference to the contents on the outside. Orders placed before 2pm Monday to Friday leave the same working day, and EU delivery takes 3 to 7 working days. Unopened items in original packaging can be returned within 30 days under our guarantee.
Why does the price differ so much between brands of MK-677?
Because the amount of compound differs. A 60-capsule bottle at 10mg contains 600mg; the same bottle at 25mg contains 1,500mg. Brands also differ in whether an independent batch certificate exists. Work out the cost per milligram from the listing and check the certificate before comparing on price alone.