MK-677 vs Retatrutide
Well Studied vs Extensively Studied
monitor Mechanism-based · 47% Both MK-677 and Retatrutide affect insulin sensitivity or blood glucose. Monitor fasting glucose and HbA1c. Consider adding an insulin sensitizer (metformin/berberine).
Molecular Data
MK-677 Retatrutide
Weight 624.77 Da 4,731.33 Da
Half-life ~24 hours ~6 days
Chain — 39 amino acids
Type Non-peptide ghrelin receptor agonist Triple GLP-1/GIP/glucagon agonist
Key Benefits
MK-677
01 97% increase in 24-hour growth hormone secretion
02 40-72% elevation in IGF-1 levels
03 Enhanced sleep quality with improved REM patterns
04 Preferential lean tissue gains of 1.1-2.7kg over 8-12 months
05 15% basal metabolic rate increase within 2 weeks
06 Oral administration (no injections required)
Retatrutide
01 Superior weight loss (24.2% at 48 weeks)
02 Improved glycemic control (HbA1c reduction up to 2.16%)
03 Enhanced cardiovascular benefits
04 Hepatic fat reduction (up to 82%)
05 Triple mechanism addresses obesity through multiple pathways
Dosing Protocols
MK-677
Start 12.5mg daily, increase to 25mg based on tolerance / Once daily, preferably at bedtime on empty stomach
Retatrutide
0.5mg starting, titrate up to 8-12mg weekly / Once weekly (same day each week)
Starting Dose (Week 1-4) 0.5mg Once weekly
Low Maintenance (Week 4-8) 1mg Once weekly
Escalation (Week 8-12) 2mg Once weekly
Moderate (Week 12-16) 4mg Once weekly
Advanced (Week 16-20) 8mg Once weekly
Maximum Efficacy (Week 20+) 12mg Once weekly
Side Effects
MK-677
Appetite stimulation (>50% of users)
Water retention (30-40%)
Lethargy (20-30%)
Fasting glucose elevation (5-15mg/dL)
Note on testosterone suppression: at doses up to 20 mg daily, MK-677 is unlikely to cause significant testosterone suppression on its own. Above 20 mg daily, the likelihood of suppression and other side effects (insulin resistance, water retention, lethargy) increases. The case report documenting 85.7% testosterone suppression involved co-administration with LGD-4033, a SARM known to be profoundly suppressive, making the SARM the likely primary driver of that suppression.
Retatrutide
Gastrointestinal effects (nausea, vomiting, diarrhea)—typically mild to moderate
Heart rate increases—common especially in first 24 weeks
Appetite suppression
Mild dehydration
Contraindications
Heart disease or congestive heart failure
Diabetes or pre-diabetes
Active cancer
Severe cardiovascular disease
Pregnancy or breastfeeding
Personal or family history of medullary thyroid carcinoma
MEN2 syndrome
Severe renal impairment
Research Evidence
MK-677 Retatrutide
Status Well Studied Extensively Studied
References 7 studies 6 studies
Latest July 2024 2025-10
FDA Approved No No
This comparison is for educational and research purposes only. Consult a healthcare professional before use.