MK-677
Ibutamoren
An oral ghrelin mimetic studied in human trials for raising growth hormone and IGF-1.
MK-677, also known as ibutamoren, is a non-peptide small molecule that mimics the hormone ghrelin. It binds the ghrelin receptor and prompts the pituitary gland to release more growth hormone (GH). Unlike most compounds in this category, it's taken by mouth, and once-daily doses raised GH and insulin-like growth factor 1 (IGF-1) for as long as two years in a trial of healthy older adults. Several randomized human trials found that GH, IGF-1 and lean mass rose, but strength didn't. A Phase IIb trial in older adults recovering from hip fracture was stopped early over a heart-failure signal. As of October 2026, MK-677 isn't approved as a drug anywhere; a Phase 3 trial in children with GH deficiency began in May 2026. FDA lists ibutamoren in Category 2 for both 503A and 503B compounding because of the heart-failure risk. This product is sold for research use only.
Read the research profile for mechanisms, citations, and safety context before comparing vendors. View the MK-677 research profile.
Key Benefits
Mechanism of Action
MK-677 is an agonist of the ghrelin receptor (GHSR) in the pituitary and hypothalamus. In a 1996 trial in 32 healthy adults aged 64-81, 25 mg/day for two weeks nearly doubled average 24-hour GH. The rise came from taller GH pulses and higher levels between pulses; the number of pulses didn't change. IGF-1 rose into the normal range for young adults within four weeks. Its effect on cortisol depends on how long it's taken. Cortisol didn't change in short trials of one to two weeks, but in a two-year trial in 65 healthy older adults, cortisol rose by an average of 47 nmol/L. Prolactin rose 23% in the 1996 trial while staying within the normal range.
Dosing Guidelines
Typical Dose
10-25 mg/day
Frequency
1x daily
Duration
8-16 weeks
Note: These figures reflect what users commonly report: 10-25 mg by mouth, often at bedtime to match overnight GH release and avoid daytime lethargy. Users say water retention becomes pronounced at 25 mg. The 8-16 week duration comes from vendor and community guidance; trials ran from one week to two years. Adult trials used 25 mg/day, and the pediatric Phase 3 uses 1.6 mg/kg/day. The empty-stomach advice is community practice; we found no study testing it. Fasting glucose rose in trials, so some users monitor it. As of October 2026, WADA prohibits MK-677 at all times (S2.2.4), and FDA lists it as a compounding safety risk.
Research & Studies
How MK-677 works, what the human trials found, the side effects seen in trials and user reports, and how users report dosing it.
Read Full ResearchWhat happens after a year or more of use, including the 2-year MK-677 trial in healthy older adults, in which GH, IGF-1 and lean mass rose and fasting glucose went up.
Read Full ResearchHow a GHRH analogue and ipamorelin, an injectable that acts on the same ghrelin receptor as MK-677, raise GH release.
Read Full ResearchPotential Side Effects
Reported side effects may include:
- - Increased hunger (trials); it faded within a few months in the 2-year trial, though some users describe it as lasting
- - Water retention and mild leg swelling (trials, users); users say it's pronounced at 25 mg
- - Lethargy or fatigue, especially on waking (user reports)
- - Reduced insulin sensitivity and higher fasting glucose (trials); one user reported fasting glucose rising from 84 to 104 mg/dL over 10 weeks
- - Raised cortisol with long-term use (47 nmol/L over a 2-year trial; no change in trials of 1-2 weeks)
- - Muscle pain (2008 trial)
- - Heart-failure signal: a Phase IIb trial in older adults recovering from hip fracture was stopped early (2011)
- - Prolactin rose 23% but stayed in the normal range (1996 trial)
- - Numbness or tingling in hands or feet (vendor lists; not traced to a study)
This information is for research purposes only. Always consult with a healthcare professional.
Popular Stacking Options
MK-677 + CJC-1295 / Ipamorelin
Some users add an injectable GHRH analogue and GHRP to MK-677, expecting a larger GH release. Ipamorelin acts on the same ghrelin receptor as MK-677, and no controlled human trial has tested any of these combinations. Some users on peptide forums describe choosing one route or the other rather than combining them.
Shop this stackMK-677 + Tesamorelin
Some users pair the two, hoping tesamorelin's effect on abdominal fat will complement MK-677's rise in IGF-1. No study has tested the combination, and in the 2-year MK-677 trial visceral fat didn't change. Tesamorelin is an FDA-approved prescription medicine (Egrifta) for excess abdominal fat in HIV-associated lipodystrophy; research-use versions aren't equivalent to it.
Shop this stackMK-677 + BPC-157 / TB-500
Users pair them for injury recovery, combining MK-677's rise in IGF-1 with BPC-157 and TB-500, whose tissue-repair data come mostly from animal studies. No study has tested the combination, and in the one MK-677 trial after hip fracture, most function measures didn't improve. As of October 2026, none of the three is approved as a drug.
Shop this stackFrequently Asked Questions
Is MK-677 a SARM or a peptide?
Neither. MK-677 is a non-peptide small molecule that acts as a ghrelin receptor agonist. It's often grouped with SARMs because it's taken by mouth and sold by the same vendors, but it doesn't act on androgen receptors.
When is the best time to take MK-677?
No trial has compared dosing times. Most users report taking it before bed, to line up with the large natural GH pulse during sleep and to sleep through the lethargy some people feel. The 1997 sleep trials also gave it at bedtime. Users who take it in the morning commonly report daytime sleepiness and stronger hunger.
Will MK-677 cause a 'GH bleed'?
The trial data say GH stays pulsatile. In a 1996 trial in older adults, 25 mg/day made GH pulses taller and raised the levels between pulses, without changing the number of pulses. Some users on peptide forums describe MK-677 as a steady 'tonic' elevation that blunts its effect over time, but in the 2-year trial IGF-1 stayed raised throughout.
How long does it take to see results from MK-677?
In trials, IGF-1 rose within two weeks, and the 2008 trial measured a 1.1 kg rise in fat-free mass after a year, with no change in strength. Users commonly report more hunger and deeper sleep within the first week. Weight often climbs faster than that, but in the 2008 trial much of the extra weight wasn't lean tissue, and users on peptide forums point out that early weight gain is largely water.
Does MK-677 require a PCT (Post-Cycle Therapy)?
MK-677 doesn't act on androgen receptors, and none of the trials we reviewed reported testosterone suppression, although testosterone wasn't their focus. Users generally don't describe post-cycle therapy for it. Its known risks lie elsewhere: higher fasting glucose, reduced insulin sensitivity and a heart-failure signal in frail older adults. Talk to a healthcare professional before using any compound that changes hormone or glucose levels.
More from this category
Compare nearby options in the same category before choosing a research product.
CJC-1295
A long-acting GHRH analogue studied in small 2006 human trials for raising growth hormone and IGF-1.
GHRP-2
A ghrelin-mimetic secretagogue studied for its strong effect on growth hormone release.
GHRP-6
A ghrelin mimetic studied for growth hormone release, with strong appetite effects reported by users.
Hexarelin
A ghrelin-mimetic GH secretagogue studied for growth hormone release and short-term heart effects.
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