⚕️ Medical Disclaimer
⚕️ Medical Disclaimer: This article is for educational and informational purposes only. It does not constitute medical advice. Consult a qualified healthcare provider before using any peptide.
What Is MK-677 (Ibutamoren)?
MK-677, also known as ibutamoren, is an oral growth hormone secretagogue that mimics ghrelin — the "hunger hormone" — to stimulate GH and IGF-1 release from the pituitary gland. Unlike injectable GH secretagogues (ipamorelin, CJC-1295, GHRP-2), MK-677 is a small molecule taken orally, typically as a capsule or liquid.
Last updated: March 2026
MK-677 was developed by Merck and has been through multiple Phase 2 clinical trials for conditions including GH deficiency, sarcopenia, and obesity. It has never received FDA approval, but it remains one of the most popular research compounds for GH optimization due to its oral bioavailability and sustained IGF-1 elevation.
The key selling point: a single daily oral dose of MK-677 elevates IGF-1 by 40-60% for 24+ hours, mimicking the effects of daily GH injections without needles. The catch: it also raises fasting glucose, increases appetite significantly, and carries risks that require monitoring. This guide covers dosing tiers, evidence, side effects, and the blood work you absolutely need before starting.
MK-677 Dosing Tiers: 10 mg, 15 mg, and 25 mg
MK-677 dosing follows a tiered approach. Higher doses produce greater IGF-1 elevation but disproportionately increase side effects, particularly glucose dysregulation and appetite stimulation.
| Dose Tier | IGF-1 Increase | GH Pulse Enhancement | Appetite Increase | Glucose Impact | Recommended For |
|---|---|---|---|---|---|
| 10 mg/day | ~30-40% | Moderate | Mild | Minimal in healthy individuals | Beginners, longevity-focused, insulin-sensitive |
| 15 mg/day | ~40-50% | Strong | Moderate | Measurable fasting glucose rise | Experienced users, recovery-focused |
| 25 mg/day | ~50-60% | Strong | Significant | Clinically relevant; monitor HbA1c | Short-term cycles (8-12 weeks), muscle building |
Timing: Take MK-677 once daily before bed. The ghrelin-mimetic mechanism amplifies natural nocturnal GH pulses, improving deep sleep (a commonly reported benefit). Taking it at night also reduces the impact of appetite stimulation during waking hours.
Cycle length: 8-12 weeks is a common approach, though some users run MK-677 continuously at 10 mg for longevity purposes. Extended use beyond 12 weeks requires quarterly blood work — specifically fasting glucose, HbA1c, and IGF-1.
Unlike injectable peptides, MK-677 does not require reconstitution. However, if you are also running injectable peptides in your stack, use our Reconstitution Calculator for those compounds.
Clinical Evidence: What Do the Trials Show?
MK-677 has the most robust clinical trial data of any GH secretagogue, with multiple placebo-controlled studies:
• IGF-1 elevation: In a 12-month study of elderly subjects, MK-677 (25 mg/day) increased IGF-1 to youthful levels (+40-60%) and increased fat-free mass by 1.1 kg vs placebo (Svensson et al., 1998, PMID: 10404019).
• Sleep quality: MK-677 increased Stage IV (deep) sleep duration by 50% and REM sleep by 20% in young healthy subjects, likely through GH-mediated mechanisms (Copinschi et al., 1997, PMID: 9349662).
• Bone density: Two-year treatment increased bone mineral density at the femoral neck in elderly women, though not in obese males (Murphy et al., 2001, PMID: 11600559).
• Nitrogen retention: MK-677 reversed diet-induced nitrogen wasting in healthy volunteers within 7 days, suggesting anticatabolic properties (Murphy et al., 1998, PMID: 9467534).
• Glucose concern: Nearly every MK-677 study reports increased fasting glucose and decreased insulin sensitivity, particularly at 25 mg. The Svensson study noted HbA1c increases from 5.2% to 5.5% over 12 months at 25 mg — not diabetic range but trending in the wrong direction.
MK-677 vs Injectable GH Secretagogues
How does oral MK-677 compare to injectable options?
| Feature | MK-677 (Oral) | Ipamorelin + CJC-1295 (Injectable) | GHRP-2 (Injectable) |
|---|---|---|---|
| Route | Oral (capsule/liquid) | SubQ injection | SubQ injection |
| Dosing frequency | 1x daily | 1-2x daily | 2-3x daily |
| IGF-1 elevation | +40-60% (sustained 24h) | +20-40% (pulsatile) | +30-50% (pulsatile) |
| Appetite increase | Significant (ghrelin pathway) | Minimal (ipamorelin) | Moderate (GHRP-2) |
| Glucose impact | Clinically significant | Minimal | Mild |
| Sleep improvement | Strong | Moderate | Moderate |
| Convenience | High (no injections) | Low (injection prep needed) | Low |
| Clinical data | Extensive (Phase 2) | Moderate | Moderate |
If glucose management is your primary concern, ipamorelin + CJC-1295 is the safer GH secretagogue choice — it elevates GH through GHRH receptor agonism without the ghrelin-mediated appetite and glucose effects. See our ipamorelin dosage guide and MK-677 vs HGH comparison for detailed comparisons.
Side Effects, Risks, and Contraindications
MK-677 side effects are dose-dependent and predictable. Monitor actively.
• Increased appetite: The #1 reported side effect. MK-677 activates the ghrelin receptor — the same pathway that makes you hungry. At 25 mg, appetite can be very aggressive. Taking the dose before bed helps mitigate daytime hunger. Consider stacking with a GLP-1 agonist if appetite is unmanageable (see drug interaction considerations in our drug interactions guide).
• Water retention and bloating: GH-mediated sodium and water retention causes mild edema, typically in the hands and face. Usually resolves within 2-3 weeks or with dose reduction.
• Elevated fasting glucose and insulin resistance: This is the critical monitoring point. At 25 mg, MK-677 can push fasting glucose above 100 mg/dL in susceptible individuals. Mandatory baseline HbA1c before starting. Contraindicated for individuals with HbA1c >5.7% (prediabetic range) or existing diabetes unless under direct medical supervision.
• Lethargy/brain fog: Some users report daytime drowsiness, especially in the first 1-2 weeks. Evening dosing usually eliminates this.
• Tingling/numbness in extremities: Carpal tunnel-like symptoms from GH-mediated soft tissue swelling. Reduce dose if persistent.
• WADA prohibited: MK-677 is banned by WADA under category S2 (Peptide Hormones, Growth Factors). Athletes subject to testing should not use it. See our peptides vs SARMs vs prohormones comparison for the full regulatory picture.
Essential Blood Work for MK-677 Users
MK-677 demands more aggressive lab monitoring than most peptides due to its glucose effects:
• Baseline (before starting): Fasting glucose, fasting insulin, HbA1c, IGF-1, CMP, lipid panel. If HbA1c is >5.6%, reconsider MK-677 or use strictly at 10 mg with monthly glucose monitoring.
• Week 4: Recheck fasting glucose and IGF-1. If fasting glucose has risen >15 mg/dL above baseline, reduce dose or discontinue.
• Week 8-12: Full panel repeat including HbA1c (now reflects 90 days of MK-677 use). IGF-1 should be in the upper third of your age-adjusted reference range — not above it.
• Post-cycle (4 weeks after stopping): Verify glucose normalization and IGF-1 return to baseline.
For the complete blood work protocol, read our essential lab guide. Track results using a peptide tracker app.
Frequently Asked Questions
Should I take MK-677 on an empty stomach? Not necessarily. MK-677 oral bioavailability is not significantly affected by food. However, taking it before bed (fasted for 2-3 hours) maximizes nocturnal GH pulse amplification and minimizes daytime appetite effects.
Can I stack MK-677 with ipamorelin? Yes — but be aware that both elevate GH/IGF-1. Monitor IGF-1 closely to ensure you stay within the upper third of your reference range, not above it. The combined GH stimulation is additive.
Does MK-677 affect testosterone? MK-677 does not directly affect testosterone, estrogen, or androgen receptors. It operates exclusively through the ghrelin/GH axis. However, improved sleep quality (a consistent MK-677 effect) can indirectly support testosterone production.
How long does it take for MK-677 to raise IGF-1? IGF-1 elevation begins within 2-4 days. Peak IGF-1 response is typically reached by week 4 and maintained throughout the cycle. IGF-1 returns to baseline within 2-4 weeks after discontinuation.
Is MK-677 technically a SARM? No — MK-677 is classified as a growth hormone secretagogue (GHS), not a selective androgen receptor modulator. It does not bind androgen receptors. However, it is frequently marketed alongside SARMs by vendors, creating confusion. See our peptides vs SARMs comparison for the full classification.
Final Word
⚕️ Medical Disclaimer: This article is for educational and informational purposes only. It does not constitute medical advice. Consult a qualified healthcare provider before using any peptide.