Peptides
MK-677 (Ibutamoren)
Also called Ibutamoren · MK677 · MK 677 · Nutrobal
MK-677 (ibutamoren) is an oral growth-hormone secretagogue, not a SARM. Most trials gave 25 mg once daily, which raised IGF-1 within two weeks. Appetite often rises and blood sugar can too; in older adults, lean mass increased without a measured gain in strength.
Dosage & duration
Published trial doses and reported use. Neither is a recommended or proven-safe regimen.
Most-studied trial dose
Published example · product-specific- Dose
- 25 mg
- How often
- Once daily, by mouth
- How long
- One week to 12 months across trials
Given to healthy older adults, obese men and young volunteers in monitored trials; not a safety endorsement for self-use.
Dose-ranging study in older adults
Published example · product-specific- Dose
- 2, 10 or 25 mg
- How often
- Once daily, by mouth
- How long
- Two- and four-week periods
GH rose with dose; at 25 mg, IGF-1 reached the young-adult range. Fasting glucose also rose.
Sources: 1
Reported use
Reported use · unapproved regimen- Dose
- 10–25 mg
- How often
- Once daily; reports describe bedtime use
- How long
- No consistent duration in the reports reviewed
Some people take it before bed to avoid daytime hunger. These are personal reports, not trial evidence.
None of the cited trials tested on/off cycling, so there is no evidence that breaks reduce side effects.
Beyond scale weight
The appetite appeal comes with other changes
What people seek
-
An oral option
More appetite, better sleep and muscle gain without injections.
What can interfere
-
Fluid and glucose
The older-adult trial found swelling, higher fasting glucose and reduced insulin sensitivity.
Mass and strength In that trial, fat-free mass increased without better strength or function; fat-free mass includes water.
Dose and timing people use
Most human trials gave 25 mg by mouth once daily; others tested 2–10 mg, and FDA counts doses from 2 to 50 mg a day across studies. Some people report taking 10–25 mg before bed to avoid daytime hunger. The sleep studies also used bedtime doses, but none of the cited trials compared morning with evening dosing. The trials gave it continuously and did not test on/off cycles, so there is no evidence that breaks reduce side effects.
How fast it works
Young men given 5 or 25 mg at bedtime had higher IGF-1 after a week. In older adults taking 25 mg daily, IGF-1 rose within two weeks and was higher again at four, reaching the usual range for young adults. Some people report hunger from the first doses; in the year-long trial, the appetite increase faded within a few months. Changes in lean mass were measured over months.
Sleep
In a small crossover study, young adults taking 25 mg at bedtime for a week had about 50% more deep (stage IV) sleep and over 20% more REM sleep than on placebo. In six older adults, compared with their own baseline after 2 mg and then 25 mg, REM sleep rose nearly 50%. These groups were small and treated for one to two weeks, so they do not show how long the effect lasts.
Muscle, fat and the scale
In the year-long trial of healthy older adults, fat-free mass rose by about 1.1 kg while it fell slightly on placebo, and body cell mass rose too. Body weight rose 2.7 kg versus 0.8 kg; total fat did not differ, but limb fat rose more on MK-677. Strength and function did not change, although the authors say the study was too small and short to judge them. In obese men taking 25 mg for eight weeks, fat-free mass rose but body fat did not fall. None of these trials studied young adults who lift weights.
Side effects and blood sugar
The most common effects in the year-long trial were increased appetite, mild leg swelling and muscle pain. Fasting glucose rose by about 5 mg/dL over the year and insulin sensitivity fell; in a four-week study it rose from about 97 to 122 mg/dL at 25 mg. Some people check fasting glucose during use, but the eight-week trial found worse glucose tolerance while fasting glucose stayed the same. In older people recovering from hip fracture, heart failure occurred in 4 people on MK-677 versus 1 on placebo and systolic blood pressure rose by about 12–16 mmHg; that trial was stopped early. FDA also lists high blood sugar, high prolactin, raised liver enzymes and high blood pressure among reasons people stopped in studies.
Drug tests and legal status
WADA lists ibutamoren under S2 (peptide hormones, growth factors and mimetics), prohibited in and out of competition. It is not an approved medicine, and FDA includes it among bulk substances that may present significant safety risks in compounding. The timing curve on this page is not a detection window.
Model details: MK-677 (Ibutamoren) · relative timing
Compare timing and buildup for this compound. The values are not blood concentrations or a measure of strength.
Shows a relative timing scenario; absolute blood concentrations are not calibrated.
Timing assumptions and sources
Historical illustrative assumption. The regulator review found no detailed clinical PK supporting a human plasma half-life. A 24 h GH/IGF effect duration is not a plasma half-life.
One 1 mg input peaks at 1 relative unit after a single dose. Other amounts scale proportionally; overlapping doses add when accumulation is on. Different compounds use separate relative scales.
- Timing half-life used
- 5 hours
- Absorption half-life assumed
- 1.25 hours
- Reference amount for the relative scale
- 1 mg
- Absorption half-life is assumed to be one quarter of the slower timescale (1.25 h); it is not a measured absorption parameter.
- A single 1-unit input has a peak of 1 relative unit; scaling and repeated-dose addition are mathematical assumptions. This normalization is independent of the example dose.
- Do not turn dog bioavailability into human availability.
- No retrieved human paired parent-drug dose, Cmax and Tmax support an absolute scale.
- Future product-specific LUM-201 work may provide calibration; no complete verified candidate was recovered here.
- FDA ibutamoren scientific review presentation, October 2024
Oral availability greater than 60% comes from dogs. Clinical publications describe long action and high oral availability without detailed clinical PK; the review found no additional clinical PK.
- Nass et al. 2008 oral MK-677 older-adult trial
A randomized trial in older adults evaluated oral 25 mg daily and GH/IGF-I/body-composition outcomes. These are not parent ibutamoren plasma-concentration endpoints.
mk-677-relative-timing-2026-10 · version 1
Common questions
Is MK-677 a SARM?
No. Ibutamoren is an oral growth-hormone secretagogue: it prompts the pituitary to release more of the body's own GH. Shops often sell it alongside SARMs.
What dose of MK-677 was studied?
Most trials used 25 mg once daily; others tested 2–10 mg, and FDA counts 2 to 50 mg a day across studies. Some people report 10–25 mg. Neither establishes a safe personal dose.
Should MK-677 be taken at night or in the morning?
Some people take it before bed to avoid daytime hunger, and the sleep studies gave it at bedtime. The cited trials did not compare morning and night dosing.
How long does MK-677 take to work?
IGF-1 rose within one to two weeks in trials. Lean-mass changes were measured over months and did not improve strength in older adults.
Is fast weight gain all muscle?
No. Fluid retention and increased food intake can both change scale weight; the cited trial did not show better strength.
Does MK-677 raise blood sugar or cortisol?
It can raise blood sugar. Fasting glucose rose from about 97 to 122 mg/dL after four weeks at 25 mg in older adults and about 5 mg/dL over a year; an eight-week trial found impaired glucose tolerance. Cortisol rose modestly in the year-long trial but not in shorter studies.
Will MK-677 show up on a drug test?
WADA bans ibutamoren at all times under S2, and FDA's review cites athletes suspended over its use. How long it stays detectable is not established here; a half-life estimate is not a detection window.
Sources Labels, studies and notes behind this guide
Catalog evidence: Human clinical trials. This describes the type of evidence, not a clinical review of every claim.
Summary and fact source checks: 2026-10-30. This records source checking, not medical review of the whole page.
Notes on the quick facts
- What it is
- A non-peptide small molecule, not a SARM; it raises the body's own GH and IGF-1.
- IGF-1 response
- IGF-1 rose within a week in young men and by two weeks in older adults.
- Main trade-offs
- Fasting glucose rose and insulin sensitivity fell in the year-long trial.
- Sport testing
- WADA lists it under S2 peptide hormones and mimetics.
- 1. Chapman et al. 1996 — MK-677 dose-ranging trial in older adults
Randomized, placebo-controlled; 32 adults aged 64–81 given placebo or 2, 10 or 25 mg once daily for 14- and 28-day periods. GH rose with dose; at 25 mg, IGF-I rose from 141 to 219 µg/L at 2 weeks and 265 µg/L at 4 weeks (young-adult range). Fasting glucose rose (5.4 to 6.8 mmol/L at 4 weeks); prolactin +23% within the normal range; cortisol unchanged.
- 2. Nass et al. 2008 oral MK-677 older-adult trial
Healthy adults aged 60–81; 25 mg oral daily, 12-month main comparison in a two-year design. Fat-free mass +1.1 kg vs −0.5 kg on placebo; body cell mass (intracellular water) +0.8 vs −1.0 kg; weight +2.7 vs +0.8 kg; total fat no different, limb fat +1.1 vs +0.24 kg; fasting glucose +0.3 mmol/L (5 mg/dL) with lower insulin sensitivity; appetite increase that subsided within a few months, transient mild leg edema and muscle pain; cortisol +47 nmol/L. No change in strength or function; authors state the study was underpowered for functional end points.
- 3. Svensson et al. 1998 — MK-677 in obese men
Randomized, placebo-controlled; 24 obese men aged 18–50 given 25 mg daily for 8 weeks. IGF-I about +40%; fat-free mass increased; total and visceral fat unchanged; basal metabolic rate up at 2 weeks but not 8; fasting glucose and insulin unchanged but oral glucose tolerance impaired.
- 4. Copinschi et al. 1997 — MK-677 and sleep quality
Bedtime dosing. Young adults (n=8): placebo, 5 and 25 mg for 7 days each; 25 mg increased stage IV sleep about 50% and REM sleep more than 20% versus placebo. Older adults (n=6): 2 mg then 25 mg for 14 days each; REM sleep rose nearly 50%. Small, short studies.
- 5. FDA ibutamoren scientific review, 2024
October 2024 advisory committee briefing: non-peptide small-molecule ghrelin-receptor agonist; not a SARM, although websites label it one; not a component of any FDA-approved drug. Studied at 2–50 mg/day for up to two years. Hip-fracture trial: heart failure in 4 (6.5%) vs 1 (1.7%) on placebo and systolic blood pressure +11.9 to 16.4 mmHg. Discontinuations across studies included hyperglycemia, hyperprolactinemia, raised transaminases and hypertension. Athlete suspensions cited.
- 6. Copinschi et al. 1996 — bedtime MK-677 in young men
Randomized crossover; 9 healthy young men given placebo, 5 or 25 mg at bedtime for 7 days each. IGF-I rose with dose; IGFBP-3 rose only at 25 mg; 24-hour cortisol unchanged.
- 7. WADA Prohibited List — ibutamoren
Official list search places ibutamoren in S2 (peptide hormones, growth factors, related substances and mimetics), prohibited at all times.
- 8. FDA ibutamoren scientific review presentation, October 2024
Oral availability greater than 60% comes from dogs. Clinical publications describe long action and high oral availability without detailed clinical PK; the review found no additional clinical PK.
- 9. Adunsky et al.: ibutamoren after hip fracture
Randomized phase IIb trial; limited functional effects and early termination for a congestive-heart-failure safety signal in this elderly population.
- 10. FDA ibutamoren safety assessment
Potential congestive-heart-failure signal in a vulnerable hip-fracture population; not a quantified risk for all users.
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