What Is MK-677 (Ibutamoren)?

MK-677 (Ibutamoren Mesylate) is a non-peptide, orally active growth hormone secretagogue developed by Merck in the late 1990s. Although it's frequently grouped with peptides, MK-677 is technically a small molecule — a ghrelin receptor agonist that stimulates GH release from the pituitary.

Key distinctions from injectable GH secretagogues:

• Oral bioavailability: No injections required — taken as a capsule or liquid
• Long half-life: Approximately 24 hours, allowing once-daily dosing
• Sustained GH elevation: Raises GH and IGF-1 levels for up to 24 hours per dose
• Not a SARM: Despite being sold alongside SARMs, MK-677 is a GH secretagogue, not a selective androgen receptor modulator

MK-677 works by mimicking ghrelin at the GHS-R1a receptor:

• Ghrelin receptor agonism: MK-677 binds to the same receptor as ghrelin and ipamorelin, triggering GH release from the pituitary
• Sustained GH pulsatility: Increases both the frequency and amplitude of GH pulses over 24 hours while maintaining natural diurnal patterns
• IGF-1 elevation: Chronic administration raises IGF-1 levels by 40–90% in studies, with effects persisting for the duration of use
• Appetite stimulation: As a ghrelin mimetic, MK-677 activates hunger signaling — a notable side effect absent from selective peptides like ipamorelin
• No HPA axis suppression: MK-677 does not significantly affect cortisol at recommended doses, though some transient elevation has been noted

Human clinical trials and research studies have documented several benefits of MK-677:

• Increased GH and IGF-1: Consistent 40–90% IGF-1 elevation with daily dosing across multiple studies
• Improved sleep quality: A notable study showed a 50% increase in REM sleep and 20% improvement in Stage 4 (deep) sleep
• Lean mass preservation: Studies in calorie-restricted subjects show MK-677 prevents muscle wasting
• Bone density support: Long-term studies demonstrate increased bone mineral density, particularly in elderly and postmenopausal subjects
• Convenience: Oral dosing eliminates the complexity of reconstitution and injection
• Nitrogen retention: Improved nitrogen balance suggests anabolic activity in research subjects

MK-677 is taken orally, typically once daily. Research protocols vary:

• Standard dose: 10–25 mg per day, taken orally
• Timing: Usually taken before bed to align GH release with natural nocturnal peaks and minimize daytime hunger
• Cycle length: Studies have run 2 months to 2 years with sustained effects; some protocols cycle 3 months on, 1 month off
• With food or fasted: Can be taken either way, though fasted administration may produce a stronger acute GH pulse

MK-677 does not require PCT (post-cycle therapy) since it does not affect testosterone or the HPG axis.

Dosages are based on published clinical research. Consult a healthcare provider for individualized guidance.

MK-677's side effect profile reflects its ghrelin-mimicking action:

• Increased appetite: The most common side effect — significant hunger stimulation, especially in the first few weeks
• Water retention and bloating: GH-mediated fluid retention is common, particularly at higher doses
• Elevated fasting blood glucose: MK-677 can increase blood sugar and reduce insulin sensitivity with prolonged use — a key safety concern
• Lethargy: Some users report drowsiness, especially with evening dosing
• Tingling and numbness: Carpal tunnel-like symptoms from elevated GH

Important: The insulin resistance concern means MK-677 should be used cautiously in individuals with pre-existing metabolic conditions. Regular blood glucose monitoring is advised during research protocols.

MK-677 quality varies widely across vendors. For verified purity, we recommend Ascension Peptides:

• 99%+ purity with independent third-party verification
• Transparent COAs available for each batch
• Capsule and liquid formats available for research convenience
• US-based shipping with discreet, fast delivery

Ascension Peptides is a trusted DailyVial affiliate partner. Given the prevalence of underdosed or contaminated MK-677 on the market, sourcing from a verified vendor is especially important.