Free Muscle MK-677: 10mg, 12.5mg and 25mg
Compare the three Free Muscle-brand MK-677 strengths: 10mg, 12.5mg and 25mg, 60 capsules per bottle. Every batch Janoshik-tested, COA on request. Research use only, 18+.
Free Muscle MK-677 Ibutamoren is our own-brand ibutamoren (MK-677, MK-0677, L-163,191, Nutrobal), a non-peptide growth hormone secretagogue and ghrelin receptor agonist, supplied as capsules in three strengths: 10mg, 12.5mg and 25mg, 60 capsules per bottle. This page is about those three listings, made to one specification and assayed batch by batch at Janoshik Analytical. If you want to see Free Muscle set against iMuscle, Yakka Strength and Thoroughbred Labs, the comparison page is MK-677, all brands. Research use only, 18+.
What is MK-677?
Ibutamoren is a spiroindoline small molecule designed at Merck in the mid-1990s to reproduce, in an orally active form, the growth hormone release triggered by the injected growth hormone releasing peptides. Its target is the growth hormone secretagogue receptor GHS-R1a, a G protein-coupled receptor expressed in the pituitary and hypothalamus and later identified as the receptor for the stomach hormone ghrelin. Activation of that receptor in trial participants increased the amplitude of growth hormone pulses and, over days to weeks, raised circulating IGF-1 and IGF-binding protein 3.
Ibutamoren is chemically unrelated to SARMs and to anabolic steroids, is not a peptide, and contains no growth hormone. It has been studied in humans in more than a dozen published trials, spanning healthy older adults, dieting volunteers, obese men, hip fracture patients and people with Alzheimer disease. It was never granted a marketing authorisation in any country and its clinical programme was discontinued. In the UK it is neither a licensed medicine nor an authorised food supplement.
What the published research reports
In a randomised, double-blind, placebo-controlled study of 32 healthy adults aged 64 to 81 (Chapman et al., 1996), two weeks of oral MK-677 increased 24-hour mean growth hormone concentration in a dose-dependent way, roughly doubling it at the highest level studied, by enhancing existing pulsatile secretion rather than adding pulses. Serum IGF-1 rose into the young-adult range by four weeks. The same participants showed a significant rise in fasting glucose, from about 5.4 to 6.8 mmol/L, and a 23 per cent rise in prolactin that stayed within the reference range.
In a cross-over study of eight healthy young men placed on a calorie-restricted diet (Murphy et al., 1998), a week of MK-677 during the second week of dieting reversed the negative nitrogen balance seen on placebo, and IGF-1 and IGF-binding protein 3 rose. The study lasted 14 days per period, involved eight people, and measured nitrogen balance rather than body composition or performance.
The largest trial, in 563 patients with mild to moderate Alzheimer disease (Sevigny et al., 2008), gave MK-677 or placebo for 12 months. Serum IGF-1 increased by around 60 per cent at six weeks and 73 per cent at 12 months, confirming that the compound engaged its target, but there was no difference from placebo on any of the four clinical outcome scales. Target engagement, in other words, did not produce a clinical effect.
Two reports from an eight-week placebo-controlled trial in 24 obese men looked beyond growth hormone. Free T3, a thyroid hormone, was higher than on placebo by eight weeks, and peak TSH rose while staying within the normal range (Svensson et al., 1999, Clin Endocrinol). Lipid changes in the same men were mostly short-lived: HDL cholesterol and triglycerides were raised at week two but no longer at week eight, total and LDL cholesterol did not change significantly, the LDL to HDL ratio was lower at eight weeks, and lipoprotein(a) was unaffected (Svensson et al., 1999, J Clin Endocrinol Metab).
These findings describe trial participants under medical supervision. They are not claims about the capsules on this page, and the elevated glucose and unchanged clinical outcomes are as much part of the record as the IGF-1 numbers.
Free Muscle MK-677 Ibutamoren: the three strengths
| Listing | Per capsule | Capsules | Total per bottle | Batch testing |
|---|---|---|---|---|
| MK-677 Ibutamoren 10mg | 10mg | 60 | 600mg | Janoshik, every batch |
| MK-677 Ibutamoren 12.5mg | 12.5mg | 60 | 750mg | Janoshik, every batch |
| MK-677 Ibutamoren 25mg | 25mg | 60 | 1,500mg | Janoshik, every batch |
All three are Free Muscle brand, capsule form, and every batch of each strength is tested for identity and purity by Janoshik Analytical. The only variable between them is the quantity of ibutamoren per capsule and therefore per bottle. We do not recommend one strength over another, because a recommendation would be dosing guidance for a compound sold for laboratory research, and we do not give that. Which listing suits a given piece of laboratory work is a matter for the researcher's own protocol.
How to compare them
Multiply strength by capsule count to get total compound per bottle, then divide the listed price by that figure for a cost per milligram. Within the Free Muscle range the arithmetic is straightforward because the capsule count is fixed at 60. When you compare against another brand, add two more checks: does a batch-specific certificate exist for the bottle you would receive, and does the stated strength refer to ibutamoren itself or to its heavier mesylate salt? Our 12.5mg listing explains why that second point can shift the real content by around 15 per cent. Our article on price per milligram covers the method, and the all-brands MK-677 page sets out every MK-677 product we stock side by side.
Batch testing and certificates of analysis
Each production batch of Free Muscle MK-677, at every strength, is sent to Janoshik Analytical, an independent laboratory, for assay. The certificate for a batch reports the identity of the compound against a reference standard and its measured purity, with the batch number, test date and laboratory details. The batch number is printed on your label: email it to us with the product name and strength and we send the Certificate of Analysis for that exact batch. We do not publish one representative certificate and apply it to every bottle, because a certificate that does not carry your batch number is not evidence about your bottle. Our lab tests page explains what each line means, and this article covers who Janoshik are and how their testing works.
Legal status in the UK
MK-677 has no MHRA marketing authorisation and is not a licensed medicine in the UK. It is not an authorised food supplement or novel food and cannot be sold for human consumption. Free Muscle supplies it strictly for laboratory research to adults aged 18 or over. Under the WADA Prohibited List, growth hormone secretagogues including ibutamoren are prohibited at all times, so the compound is incompatible with tested sport. Our MK-677 legal status in the UK page sets out the position in full.
Storage and handling
Store the sealed bottle in a cool, dry place away from light and heat, and reseal it after each opening. Do not transfer capsules to unlabelled containers. Note the batch number in your records at receipt so any certificate request or query can be matched to the material. Keep out of reach of children and pets and follow normal laboratory good practice when handling.
Delivery and returns
Free Muscle is the trading name of FreeMuscle, a business registered in Andorra, with UK operations and dispatch in Scunthorpe. Delivery is free and tracked on every order, the packaging is plain, and an order received before 2pm on a working day (Monday to Friday) is processed that same day. Customers in the EU should allow 3 to 7 working days. If an item arrives and stays unopened, it can be returned within 30 days under our guarantee. See delivery and returns.
Related reading
- MK-677 (Ibutamoren): What the Research Says
- What Is Janoshik Analytical? Third-Party Testing Explained
- How to Read a Certificate of Analysis (COA)
- MK-677 by brand: what actually differs when the molecule is the same
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):4249-4257. PMID: 8954023.
- Murphy MG, et al. MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism. J Clin Endocrinol Metab. 1998;83(2):320-325. PMID: 9467534.
- Sevigny JJ, et al. Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial. Neurology. 2008;71(21):1702-1708. PMID: 19015485.
- Svensson J, et al. Discrepancy between serum leptin values and total body fat in response to the oral growth hormone secretagogue MK-677. Clin Endocrinol (Oxf). 1999;50(4):451-456. PMID: 10468903.
- Svensson J, et al. Treatment of obese subjects with the oral growth hormone secretagogue MK-677 affects serum concentrations of several lipoproteins, but not lipoprotein(a). J Clin Endocrinol Metab. 1999;84(6):2028-2033. PMID: 10372705.
Last reviewed: October 2026.
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. Summaries of published research describe study findings and are not claims about any product.
Frequently asked questions
What is the difference between the 10mg, 12.5mg and 25mg Free Muscle MK-677?
Only the quantity of ibutamoren in each capsule. All three hold 60 capsules, and every batch of each strength is assayed by Janoshik Analytical. Per bottle that works out at 600mg, 750mg and 1,500mg of compound respectively. We do not recommend a strength, because the product is sold for laboratory research only.
Which Free Muscle MK-677 strength should I choose?
We do not advise on this. MK-677 is supplied for laboratory research, not for human use, and recommending a strength would be dosing guidance we are not in a position to give. Choose according to your research protocol, compare the total milligrams per bottle, and request the batch certificate for whichever listing you order.
Is Free Muscle MK-677 tested by an independent laboratory?
Yes. Every batch of every strength is sent to Janoshik Analytical, an independent laboratory, for identity and purity testing. The batch number is on the label. Email it to us with the product name and we send the Certificate of Analysis for that specific batch. We do not reuse one certificate across batches.
Where can I compare Free Muscle MK-677 with other brands?
On our all-brands MK-677 collection page, which lists Free Muscle alongside iMuscle, Yakka Strength and Thoroughbred Labs with strength, capsule count and batch-testing status for each. This page covers only the three Free Muscle strengths. The molecule is the same across brands; what differs is quantity per capsule and whether a batch certificate exists.
Is MK-677 legal to buy in the UK?
Yes, in the sense that ibutamoren is not scheduled under the Misuse of Drugs Act, so purchase is lawful. What it lacks is any MHRA licence or food-supplement authorisation, which is why it may only be supplied for laboratory research, never for consumption, and only to adults aged 18 or over. Athletes should note that WADA prohibits it at all times. Our legal status page goes through the position in full.
Is MK-677 a peptide or a SARM?
Neither. MK-677 is a non-peptide small molecule that acts at the ghrelin receptor (GHS-R1a) to stimulate growth hormone release. Peptides such as ipamorelin act at the same receptor but are amino-acid chains. SARMs act at the androgen receptor and are a different class altogether. Ibutamoren is often grouped with both in shops, but it belongs to neither class.
Will MK-677 be detected in a drugs test for sport?
Ibutamoren is listed by WADA under growth hormone secretagogues and is prohibited at all times. Accredited anti-doping laboratories have methods for detecting it and its metabolites. Anyone who competes in tested sport should treat it as a banned substance regardless of brand or strength.
What is the half-life of MK-677?
We do not quote one, because we have not found a verified human elimination half-life in the published trial reports, and we could not trace the figures repeated online to a published source. The trials measured something different: growth hormone sampled every 20 minutes over 24 hours, with the 24-hour average raised after two weeks (Chapman 1996), and IGF-1 still raised after 12 months of treatment in the Alzheimer trial (Sevigny 2008). That describes hormone markers in supervised studies, not guidance for use.