MK-677 vs GHRP-6: Oral Mimic vs Injected Peptide
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[GH peptides · Comparison]

MK-677 vs GHRP-6: how do they differ?

Route · Human trials · FDA status

Short answer: Both act on the ghrelin receptor to release growth hormone. GHRP-6 is an injected six-amino-acid peptide; MK-677 (ibutamoren) is a non-peptide pill that acts on the same receptor.1 MK-677 has longer human trials, up to 2 years, which also found higher fasting glucose.2 Neither is FDA approved, and FDA lists both as compounding safety risks.3 No study compares them.

How do MK-677 and GHRP-6 compare side by side?

From published human trials, FDA compounding lists and the 2026 WADA List. Neither has a US label.
MK-677 (ibutamoren)GHRP-6
What it isNon-peptide ghrelin mimetic taken by mouth12Six-amino-acid peptide4
Route in human studiesBy mouth, once daily5Mostly into a vein, as a one-off GH test64
Longest human study2 years in 65 healthy adults aged 60 to 812Single-dose studies in the sources we checked46
Doses studied2, 10 or 25 mg daily;5 25 mg daily for up to 2 years2100, 200 and 400 mcg/kg as one IV dose (pharmacokinetic study)4
Half-lifeNot stated in the trial abstracts cited hereAbout 2.5 hours after one IV dose4
Effect on IGF-125 mg daily raised IGF-1 from 141 to 265 mcg/L at 4 weeks in older adults5Prolonged GHRP use raises IGF-1, per a 1997 review1
GlucoseFasting glucose 5.4 to 6.8 mmol/L at 4 weeks;5 up 0.3 mmol/L over a year with lower insulin sensitivity2FDA cites a rise in blood sugar from lower insulin sensitivity3
FDA compounding status503A and 503B Category 2; FDA cites a hip fracture trial stopped early for a heart failure signal3503B Category 2 since September 29, 20233
SportWADA S2.2.4 (ibutamoren named)7WADA S2.2.4 (named)7

Reviewed . Half-life figures are shown only where the value Dose Track uses agrees with the cited source.

GHRP-6 was the first growth hormone releasing peptide studied widely in people. Non-peptide drugs were then built to act on the same receptor, and a 1997 review called MK-0677 (MK-677) the most interesting of them.1 The practical difference is the route: MK-677 works as a once-daily pill, while GHRP-6 has been studied mainly as an IV test dose.56

What did the MK-677 trials find?

  • 4 weeks in older adults: 25 mg a day raised average 24-hour GH by 97% and brought IGF-1 into the young-adult range; fasting glucose rose from 5.4 to 6.8 mmol/L.5
  • 2 years in older adults: fat-free mass rose 1.1 kg vs a 0.5 kg fall on placebo, but strength and function did not change. Fasting glucose rose 0.3 mmol/L, insulin sensitivity fell and cortisol rose; increased appetite, mild leg swelling and muscle pain were the most frequent side effects.2
  • Hip fracture recovery: 123 older patients on 25 mg a day or placebo. IGF-1 rose, gait speed improved slightly, but most function measures did not, and the trial was stopped early for a heart failure safety signal.8

What is known about GHRP-6 in people?

Most human GHRP-6 studies gave one dose into a vein to test how much GH the pituitary could release. The response was lower in GH deficiency than in healthy children, with overlap between the groups.6 One study measured an elimination half-life of about 2.5 hours in nine healthy men.4 We found no long-term GHRP-6 trial in the sources we checked.

No study has compared the two directly. These are study protocols, not personalized advice; confirm any dosing with your prescriber. More detail: the MK-677 (Ibutamoren) and GHRP-6 guides.

This page summarizes labels and published studies. It is not personalized medical advice; confirm any dose or change with your prescriber.
GHRP-2 vs GHRP-6: how do they differ?Two six-amino-acid ghrelin mimics Ipamorelin vs MK-677: how do they differ?Injected peptide vs daily oral ghrelin mimetic HGH vs MK-677: how do they differ?Replacing growth hormone vs prompting your own

Frequently asked questions

Is MK-677 a peptide like GHRP-6?+
No. MK-677 is a non-peptide drug taken by mouth that acts on the same ghrelin receptor as GHRP-6.1
Does MK-677 raise blood sugar?+
In trials, yes: fasting glucose rose from 5.4 to 6.8 mmol/L at 4 weeks in one study and insulin sensitivity fell in a 2-year study.52
Why does FDA list MK-677 as a safety risk?+
FDA cites the potential for congestive heart failure, pointing to a hip fracture trial stopped early for that signal.38
Are they allowed in sport?+
No. The 2026 WADA List names ibutamoren (MK-677) and GHRP-6 under S2.2.4.7
Can I track MK-677 or GHRP-6 in Dose Track?+
Yes. MK-677 is built in as an oral compound and GHRP-6 as an injectable with reconstitution math, both with reminders.

Sources

  1. Ghigo E, et al. Growth hormone-releasing peptides. Eur J Endocrinol. 1997;136:445-60.
  2. Nass R, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med. 2008;149:601-11.
  3. FDA. Certain bulk drug substances for use in compounding that may present significant safety risks (Category 2 and nominated-but-withdrawn lists). Updated April 2026.
  4. Cabrales A, et al. Pharmacokinetic study of growth hormone-releasing peptide 6 (GHRP-6) in nine male healthy volunteers. Eur J Pharm Sci. 2013;48:40-6.
  5. Chapman IM, et al. Stimulation of the GH-IGF-I axis by daily oral administration of a GH secretagogue (MK-677) in healthy elderly subjects. J Clin Endocrinol Metab. 1996;81:4249-57.
  6. Pombo M, et al. Growth hormone releasing hexapeptide-6 (GHRP-6) test in the diagnosis of GH-deficiency. J Pediatr Endocrinol Metab. 1996;9 Suppl 3:333-8.
  7. World Anti-Doping Agency. The 2026 Prohibited List, in force January 1, 2026 (English text as published in the Dutch Treaty Series, Tractatenblad 2026, 25).
  8. Adunsky A, et al. MK-0677 (ibutamoren mesylate) for the treatment of patients recovering from hip fracture: a phase IIb study. Arch Gerontol Geriatr. 2011;53:183-9.

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