MK-677
Also known as: Ibutamoren, Nutrobal, L-163,191
Popular For
Muscle building, sleep improvement, appetite increase
Key Facts: MK-677
- Category
- Growth Hormone
- FDA Status
- Not FDA Approved
- Clinical Status
- Investigational - Phase II trials halted (safety concerns). FDA enforcement ongoing (2025)
- Administration
- Oral
- Typical Dose
- 10-25 mg daily
- Frequency
- Once daily, often before bed
- Evidence Level
- Human Trials
- Duration
- 8-12 weeks or longer
Mechanism of Action
MK-677 binds to ghrelin receptors (GHSR) in the brain, stimulating sustained GH release and increasing IGF-1 levels. Unlike injectable GHRPs, it is orally bioavailable and has a long half-life providing 24-hour GH elevation.
Research Summary
Studies show increases in GH and IGF-1 levels, improved sleep quality, and increased lean body mass. However, a clinical trial was stopped early due to heart failure concerns in elderly patients. FDA lists MK-677 as having 'significant safety risks due to potential for congestive heart failure.' December 2025: FDA issued warning letters to companies selling MK-677. Never received FDA approval and remains an unapproved drug.
Dosing Information
Typical Dosingⓘ
Community experience
10-25 mg daily
10-50 mg daily
Once daily, often before bed
Oral GH secretagogue. Can cause water retention, increased appetite, and blood sugar issues. Some cycle it, others run year-round.
Research Dosingⓘ
Scientific studies
Doses from research studies
Doses from Studies
Duration
8-12 weeks or longer
Administration
Oral
Timing & Administration
Best Time to Take
Before bed
Once daily, consistently at the same time
Food Recommendation
With or without food
Why This Timing?
MK-677 can cause drowsiness and hunger. Evening dosing minimizes daytime appetite increase and supports sleep-related GH release.
Possible Side Effects
Not everyone experiences these effects. Individual responses vary based on dosage, duration, and personal factors.
- ●Increased appetite and hunger
- ●Weight gain
- ●Water retention/edema
- ●Insulin resistance
- ●Elevated blood glucose/hyperglycemia
- ●Anxiety
- ●Muscle or joint pain
- ●Numbness/tingling
- ●Risk of heart failure (FDA concern - clinical trial halted)
- ●May negatively impact bone mineral density
- ●NOT FDA approved - FDA issuing warning letters (2025)
References
Related Peptides
Peptides commonly compared with MK-677 or used in similar applications.
Ipamorelin
Clinical TrialsA selective growth hormone secretagogue that stimulates GH release without significantly affecting cortisol or prolactin. Considered one of the safest GHRPs.
Growth HormoneCJC-1295
Clinical TrialsA synthetic analog of growth hormone-releasing hormone (GHRH) that stimulates GH release from the pituitary. Often combined with a GHRP like Ipamorelin for synergistic effects.
Growth HormoneTesamorelin
FDAAn FDA-approved GHRH analog used to reduce excess abdominal fat in HIV-infected patients with lipodystrophy. New F8 formulation (Egrifta WR) approved March 2025 allows weekly reconstitution vs daily.
Growth HormoneGHRP-6
Clinical TrialsOne of the first synthetic GH secretagogues developed. Strongly stimulates GH release and significantly increases appetite through ghrelin receptor activation.
Growth HormoneGHRP-2
Clinical TrialsA synthetic hexapeptide that potently stimulates GH release. More potent than GHRP-6 with less appetite stimulation, but still elevates cortisol and prolactin.
Growth HormoneSermorelin
PreclinicalA truncated analog of natural GHRH containing the first 29 amino acids. Previously FDA-approved for pediatric GH deficiency, now used off-label for adult hormone optimization.
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