MK-677
Also known as Ibutamoren, Nutrobal
It raises growth hormone and lean mass in trials, without clear gains in strength. FDA flags a possible heart failure risk.
Information only. Not medical advice. Talk to a doctor before you start, stop or change anything.
MK-677 is not technically a peptide. It is a small-molecule drug, listed here because it is sold and discussed alongside peptides.
What people claim
- Builds muscle and burns fat
- A legal, oral alternative to growth hormone
- Improves sleep and recovery
What the evidence shows
- In a 2-year randomized trial in healthy older adults, it raised growth hormone and fat-free mass, but strength and function did not change.[1]
- In a 2-month study of obese men, fat-free mass rose while glucose control got worse.[2]
- We found no good trial in young, healthy people training for muscle, which is who mostly uses it.
- "Legal" is misleading. It is not an approved drug and cannot lawfully be sold as a dietary supplement in the US.[3]
Known risks
- FDA says it poses significant safety risks because of possible congestive heart failure in certain patients. A clinical trial was stopped early over this concern.[3][4]
- Fasting blood sugar rose and insulin sensitivity fell in the 2-year trial.[1]
- Increased appetite, fluid retention, and joint or muscle pain are commonly reported.[1][3]
- Long-term safety is not established, and it is banned in sport.[3]
Reported side effects
Moderated user reports are not open yet, so nothing is shown here. They will be labelled as unverified personal accounts.
Legal status
A summary, not legal advice. Rules change, and sport bans are separate.
Unapproved
Not legal in supplements. FDA lists it in Category 2 for compounding, citing heart failure risk.
Unlicensed
No licensed medicine contains it.
Not approved
No approved product.
Not authorised
No authorised medicine. National rules on possession and import differ.
Sources
- 1.Effects of an oral ghrelin mimetic on body composition in healthy older adultsAnnals of Internal Medicine, 2008
- 2.Two-month treatment of obese subjects with MK-677Journal of Clinical Endocrinology and Metabolism, 1998
- 3.Performance enhancing substance: MK-677 (ibutamoren)Operation Supplement Safety, US Department of Defense
- 4.Bulk drug substances that may present significant safety risksUS FDA
Profile last checked 7 Nov 2026.