Verified July 2026 · Cited to primary sources

MK-677 (Ibutamoren): Evidence Grade C. Early / foreign human data only.

Grade CResearch-onlySafety: amber

The honest verdict

The most-studied and only orally-active option in this group, with genuine 2-year human RCT data behind it, which is why it grades C and not D. But the same trial that proves it works also shows the catch: modest lean-mass gain, no functional benefit, and worse insulin sensitivity. Not FDA-approved, research-only, and a poor idea for anyone with blood-sugar concerns.

MK-677 (Ibutamoren) at a glance

Class
Orally-active growth hormone secretagogue (ghrelin/GHS-R1a agonist), a NON-peptide small molecule, not a peptide
Mechanism
Non-peptide agonist of the ghrelin receptor (GHS-R1a) that mimics ghrelin to drive sustained, roughly physiological increases in growth hormone and IGF-1. Because it is orally bioavailable and long-acting, one daily dose keeps GH/IGF-1 elevated, unlike the injectable peptide GHRPs. That same sustained GH/IGF-1 elevation is what drives its main downside: reduced insulin sensitivity and higher fasting glucose.
Also known as
Ibutamoren, Ibutamoren mesylate, MK-0677, L-163191, Oratrope
Research applications
  • Body composition in older adults (2-year RCT)
  • Bone turnover in elderly adults (RCT)
  • GH deficiency, frailty, catabolic states, and NAFLD research
  • Sleep-architecture research
Forms
Oral capsule / tablet (research supply), Oral liquid / solution (research supply)
Legal status
Research-only
WADA (anti-doping)
Prohibited at all times (S2.2.4, growth hormone secretagogues), ibutamoren (MK-677) named on the WADA Prohibited List
Evidence grade
Grade CEarly / foreign human data only

How we grade evidence

Every grade comes from a fixed A to F rubric: human-trial strength, not hype or affiliate status. Last verified July 6, 2026.

What is MK-677 (Ibutamoren)?

The odd one out: MK-677 is not a peptide, it is an orally-active small-molecule ghrelin mimetic, which is why people take it as a daily capsule instead of an injection. It has the best human evidence in this group by far, including a 2-year randomized trial, but that trial is also the cautionary tale: it raised lean mass a little while measurably worsening insulin sensitivity and blood sugar.

Non-peptide agonist of the ghrelin receptor (GHS-R1a) that mimics ghrelin to drive sustained, roughly physiological increases in growth hormone and IGF-1. Because it is orally bioavailable and long-acting, one daily dose keeps GH/IGF-1 elevated, unlike the injectable peptide GHRPs. That same sustained GH/IGF-1 elevation is what drives its main downside: reduced insulin sensitivity and higher fasting glucose.

How strong is the evidence for MK-677 (Ibutamoren)?

MK-677 has real, multi-study human RCT data, well beyond anything the GHRPs have: a 2-year double-blind trial in older adults (Nass 2008) and randomized bone-turnover trials (Murphy 1999). It reliably raises GH and IGF-1 into a youthful range and modestly increases fat-free mass. But it is not FDA-approved, the 2-year trial showed no improvement in strength or function despite the lean-mass gain, and it measurably reduced insulin sensitivity and raised fasting glucose. Real human efficacy on a surrogate (FFM, IGF-1) but no approval and a meaningful metabolic downside puts it at C, the top of this group.

Primary sources (3)

  1. Nass 2008, Ann Intern Med, 2-year RCT of oral MK-677 in healthy older adults: increased fat-free mass and IGF-1 to youthful range, but raised fasting glucose and reduced insulin sensitivity
  2. Murphy 1999, J Bone Miner Res, oral MK-677 increased markers of bone turnover in 187 elderly adults (randomized, placebo-controlled)
  3. WADA Prohibited List, growth hormone secretagogues incl. ibutamoren (MK-677) banned at all times (S2.2.4)

What is MK-677 (Ibutamoren) used for?

MK-677 (Ibutamoren) is marketed for the goals below. See how it ranks against other peptides in each, by evidence, not hype.

Best peptides for Muscle Growth →Best peptides for Recovery & Healing →Best peptides for Sleep →

What does MK-677 (Ibutamoren) cost, and how do you access it legally?

Typical cost

UNKNOWN

No FDA-approved or compoundable route to price. Sold only as a research chemical, which we do not price. If you see it marketed as a supplement, that is a mislabeling and legality problem, not a legitimate market.

No legal supervised access route right now.

MK-677 (Ibutamoren) has no compliant US route today. Vials sold "for research use only" are a gray-market fig-leaf, not a legal loophole, so we don't link them. If you pursue MK-677 (Ibutamoren), do it with a licensed clinician, and re-check its legal status first.

Is MK-677 (Ibutamoren)safe? Side effects & risks

Limited human safety data, no major documented harms

Never FDA-approved despite reaching multi-year trials (development was not carried to approval). The best-documented harm signal in this whole class comes from MK-677 itself: in the 2-year trial it raised fasting blood glucose and reduced insulin sensitivity, which matters for anyone with prediabetes, diabetes or metabolic-syndrome risk. Other reported effects: increased appetite, mild lower-limb edema (water retention), muscle pain, and transient fatigue. Because it sustains GH/IGF-1 around the clock rather than in pulses, the theoretical long-term IGF-1 concern is more relevant here than with short-acting peptides. As with all research-chemical supply, purity and dosing are unverified; FDA testing found roughly 40% of online/compounded products mislabeled.

Medical disclaimer: This page is independent editorial information, not medical advice, and Best Peptide For That is not a medical provider. We do not provide dosing. Talk to a licensed clinician before starting, stopping, or changing any peptide or medication. Full medical disclaimer.

FAQ

MK-677 (Ibutamoren) FAQ

Is MK-677 a peptide?

No, and this is the common misconception. MK-677 (ibutamoren) is a non-peptide small molecule. It mimics the peptide hormone ghrelin at the same receptor, which is why it is grouped with GH secretagogues, but chemically it is not a peptide, and unlike the GHRPs it is taken orally rather than injected.

Does MK-677 actually work?

For raising GH, IGF-1 and fat-free mass, yes, and it has 2-year randomized human data showing it (Nass 2008). The honest caveat is that the same trial found no improvement in muscle strength or physical function despite the extra lean mass, and it worsened insulin sensitivity.

What is the main risk of MK-677?

Insulin resistance. The 2-year trial showed increased fasting glucose and reduced insulin sensitivity. That makes it a bad choice for anyone with prediabetes, type 2 diabetes, or metabolic-syndrome risk. Water retention, increased appetite and muscle pain are also common.

Is MK-677 legal or FDA-approved?

It is not FDA-approved and never completed development to approval. It cannot be legally sold as a supplement or compounded as a drug. It is a research chemical, and it is banned in sport at all times under WADA S2.2.4.

From our portfolio

Tracking MK-677 (Ibutamoren)?

Titrate is an iOS app for logging doses, schedules and progress over time, with a reconstitution calculator built in. It tracks, it does not prescribe.

Get Titrate for iOS →

Keep reading

Grade D

BPC-157

The most-hyped, least-human-proven "healing" peptide. Extensive rodent data, zero published human trials.

Grade D

TB-500

The other half of the "wolverine stack." Soft-tissue recovery claims, but only animal data for the fragment actually sold.

Grade D

KPV

An anti-inflammatory tripeptide studied for gut and skin inflammation. Promising in cells and animals, untested in humans.

How we grade the evidence →Are peptides safe? →FDA peptide status 2026 →

The monthly peptide evidence brief.

What the research and the FDA actually say, in one short email a month. Unsubscribe anytime.

No spam. We never sell your email. Editorial policy.