MK-677 (ibutamoren) is an oral drug that copies the hunger hormone ghrelin and makes the body release more growth hormone (GH), which raises IGF-1. It is not a SARM and it is not approved as a medicine anywhere we could find. In human trials it added about 1 kg of fat-free mass over a year but did not improve strength, and it raised blood sugar, caused swelling and increased appetite. One trial in frail older adults was stopped early because of a heart-failure signal, and the FDA now lists it as a substance that may present significant safety risks.

This review covers what MK-677 is, how it works, every human trial we could verify, what it does and does not do, its side effects, the blood sugar and heart findings, its legal and sport status, and the questions people search for most. Every number links to its source.

What is MK-677 (ibutamoren)?

MK-677 is the research code for ibutamoren mesylate. You will also see it as MK-0677, L-163,191, LUM-201 and, on some seller websites, Nutrobal (FDA warning letter, 2025). Merck researchers described it in 1995 as an orally active growth hormone secretagogue, a drug that makes the pituitary release GH (Patchett 1995).

Merck tested it in older adults, people with GH deficiency, obesity, osteoporosis, hip fracture and Alzheimer’s disease, but never brought it to market. In its 2024 review the FDA wrote that no FDA-approved drug contains ibutamoren and that Merck discontinued development in 1999; Lumos Pharma later licensed it and renamed it LUM-201 for children with GH deficiency (FDA 2024). A 12-month Phase 3 trial of LUM-201 in children has been recruiting since May 2026 (NCT06948214).

Fact MK-677 (ibutamoren)
Drug class Growth hormone secretagogue (ghrelin receptor agonist)
Taken as By mouth (capsules, tablets or liquid); trials used tablets or weight-based oral doses
Approved as a medicine? No. No FDA-approved drug contains it; we found no approval anywhere else
Furthest stage Phase 3 in children with GH deficiency (as LUM-201), recruiting since May 2026
Is it a SARM? No (see below)
Human half-life Not published. One dose raises GH for about 24 hours
Banned in sport? Yes, at all times (WADA S2.2.4)

Is MK-677 a SARM?

No. SARMs (selective androgen receptor modulators) such as ostarine, LGD-4033 and RAD-140 act on the androgen receptor, the same receptor testosterone uses. MK-677 does not. It acts on the ghrelin receptor and works through your own growth hormone. The FDA states this plainly in its 2024 review: “MK-677 is a GHS, not a SARM” (FDA 2024).

The anti-doping rules agree. WADA lists SARMs under S1 (anabolic agents) but lists ibutamoren (MK-677) under S2.2.4, with growth hormone secretagogues and their mimetics (WADA 2026). It gets called a SARM because online shops sell it next to SARMs; the FDA notes it is “marketed online … as a selective androgen receptor modulator (SARM)” for bodybuilding (FDA 2024).

How does MK-677 work?

MK-677 activates the ghrelin receptor (GHS-R1a) on GH-producing cells in the pituitary and on GHRH neurons in the hypothalamus. Both routes end in more GH release, and GH then tells the liver and other tissues to make more IGF-1 (FDA 2024). Because ghrelin is also a hunger hormone, appetite goes up too.

  • GH pulses get bigger or more frequent. In older adults, 25 mg/day raised mean 24-hour GH by 97% after two weeks, mainly by making existing pulses taller (Chapman 1996). In young men it increased the number of small GH pulses (Copinschi 1996).
  • IGF-1 rises with the dose. IGF-1 went from 141 to 265 µg/L after four weeks on 25 mg/day in adults aged 64 to 81, into the range of young adults (Chapman 1996).
  • It lasts about a day. No human plasma half-life has been published; the FDA found no detailed human pharmacokinetic data and quotes a 1997 paper saying one dose is “long-acting (24 hours)” (FDA 2024). Half-life numbers on vendor sites are not backed by a published human study.
  • The effect may fade in animals. In rats, daily dosing for six weeks left GH no higher than in untreated rats (FDA 2024). In people the effect held: after 12 months, GH was still 1.8 times and IGF-1 1.5 times baseline (Nass 2008).

Want to see how MK-677 compares with other compounds on half-life, evidence and suppression? Use the compare tool or browse the SARMs and peptides database.

MK-677 human trials: every study we verified

MK-677 is one of the better-studied compounds sold online. We counted 17 distinct human trials with published or posted results. Most used 25 mg once a day. Most were in patients or older adults; the three in healthy young adults lasted about a week each, and none was in people who train.

Study Who took part Dose Length Main finding
Copinschi 1996 9 healthy young men 5 or 25 mg/day at bedtime 7 days per period IGF-1 rose with dose; more GH pulses; 24-hour cortisol unchanged
Chapman 1996 32 healthy adults aged 64–81 2, 10 or 25 mg/day 28 days GH +97%; IGF-1 141 → 265 µg/L; fasting glucose 5.4 → 6.8 mmol/L
Chapman 1997 9 men aged 17–34 with severe childhood-onset GH deficiency 10 or 50 mg/day 4 days per period IGF-1 +52% (10 mg) and +79% (50 mg); insulin and after-meal glucose rose
Copinschi 1997 8 young and 6 older adults 2, 5 or 25 mg/day at bedtime 7–14 days About 50% more deep (stage IV) sleep and over 20% more REM sleep in young adults on 25 mg
Murphy 1998 8 healthy adults on a calorie-restricted diet 25 mg/day 7 days Nitrogen balance +0.31 vs −1.48 g/day on placebo (less protein breakdown)
Svensson 1998 24 obese men aged 18–50 25 mg/day 8 weeks IGF-1 about +40%; fat-free mass up; total and belly fat unchanged; glucose tolerance worse
Murphy 1999 187 adults aged 65+ (three trials) 5 to 50 mg/day 2–9 weeks IGF-1 +55–94%; bone formation and breakdown markers both rose
Codner 2001 18 children with GH deficiency 0.2 or 0.8 mg/kg/day 7–8 days GH, IGF-1 and IGFBP-3 rose in some children
Murphy 2001 292 women aged 64–85 with low bone density 25 mg/day ± alendronate 12–18 months With alendronate, femoral-neck density +4.2% vs +2.5%; no extra gain elsewhere
Bach 2004 161 adults 65+ after hip fracture 25 mg/day 6 months IGF-1 +84% vs +17%; physical function not significantly better
Nass 2008 65 healthy adults aged 60–81 25 mg/day 12 months (+12-month extension) Fat-free mass +1.1 kg vs −0.5 kg; no change in strength or function; fasting glucose +5 mg/dL
Sevigny 2008 563 adults with Alzheimer’s disease 25 mg/day 12 months IGF-1 +72.9%; no effect on disease progression
Adunsky 2011 123 older adults after hip fracture 25 mg/day 24 weeks Gait speed slightly better, most tests not; stopped early for a heart-failure signal
Campbell 2018 26 adults on hemodialysis 25 mg/day About 30 days per period IGF-1 rose 65% more than on placebo; no serious drug-related side effects
Bright 2021 (via FDA) 68 children with GH deficiency 0.4 or 0.8 mg/kg/day 6 months Height velocity 6.0–6.9 cm/year vs 4.5 on placebo and 11.1 on injected GH
OraGrowtH210 104 children with GH deficiency 0.8, 1.6 or 3.2 mg/kg/day 6 months (primary result) Height velocity 6.8–8.2 cm/year vs 10.6 on injected GH
NCT05364684 12 adults with fatty liver disease 25 mg/day 6 months, no placebo Liver fat did not fall (7 people analyzed)

The doses in this table are what the trials gave to their participants, under medical supervision. They are not dosing advice. Our MK-677 dosage page goes through the doses in detail.

What MK-677 does: effects by strength of evidence

Effect What the trials found Evidence
GH and IGF-1 Up. GH 1.8-fold and IGF-1 1.5-fold after 12 months on 25 mg/day; IGF-1 back to baseline within a month of stopping (Nass 2008) Trial
Fat-free mass Up. +1.1 kg vs −0.5 kg on placebo over 12 months; also up in obese men over 8 weeks. Part of the gain may be water (Nass 2008, Svensson 1998) Trial
Strength and physical function No clear change in healthy older adults or after hip fracture (Nass 2008, Bach 2004) Trial
Body fat No change in total or belly fat. Limb fat rose 1.1 vs 0.24 kg and body weight 2.7 vs 0.8 kg on placebo (Nass 2008) Trial
Appetite Up in 29 of 43 people vs 8 of 22 on placebo; settled within a few months for many (Nass 2008) Trial
Sleep About 50% more deep sleep and over 20% more REM sleep in young adults; nearly 50% more REM sleep in older adults. Only 14 people (Copinschi 1997) Trial (small)
Protein breakdown while dieting Reduced over 7 days in 8 people (Murphy 1998) Trial (small)
Bone Turnover up; density gain only at the femoral neck when combined with alendronate (Murphy 2001) Trial
Cholesterol LDL down 5.4 mg/dL in older adults; LDL/HDL ratio down in obese men (Nass 2008, Svensson 1999) Trial
Alzheimer’s disease No effect on progression in 563 patients (Sevigny 2008) Trial
Height in children with GH deficiency Faster growth than placebo but slower than injected GH; no trial in adults or healthy teens (NCT04614337) Trial
Hair, skin and nails Not tested in any trial we found; reports are anecdotal Anecdotal

The short version: MK-677 reliably raises GH and IGF-1 and adds some lean mass and body weight. It has not been shown to make people stronger or fitter, and it did not help in the diseases it was tested for. The FDA concluded there is insufficient information to support its effectiveness for any of the uses it reviewed (FDA 2024).

MK-677 results: what happens and when

People search for timelines, so here is what the trials measured at each point. These are averages from controlled studies, not promises.

When What the studies measured
First dose A sharp GH rise: peak GH 55.9 µg/L on day 1 in dieting adults, smaller (22.6 µg/L) after a week (Murphy 1998)
1–2 weeks IGF-1 up (219 µg/L at 2 weeks from 141); fasting glucose already 25% higher in older adults (Chapman 1996, FDA 2024); sleep changes in the 7- to 14-day sleep study (Copinschi 1997)
2–8 weeks Fat-free mass up in obese men by week 8; basal metabolic rate up at 2 weeks but not at 8 (Svensson 1998)
First months More appetite, mild leg swelling and muscle pain, often short-lived (Nass 2008)
12 months Fat-free mass +1.1 kg, weight +2.7 kg, no strength gain, fasting glucose +5 mg/dL (Nass 2008)
After stopping IGF-1 back to baseline within about a month (Nass 2008)

For reader-submitted transformations and what to make of them, see MK-677 before and after results and the 12-week MK-677 log.

MK-677 side effects

The FDA’s 2024 review summed up the trial data like this: “there are serious safety concerns related to ibutamoren mesylate use including hyperglycemia, liver enzyme elevations, edema and fluid overload, and CHF [congestive heart failure] in elderly patients recovering from hip fracture” (FDA 2024).

Side effect How often in trials Evidence
Increased appetite 67% vs 36% on placebo over 12 months (Nass 2008) Trial
Swelling (edema), water retention Mild leg swelling in 19 of 43 vs 6 of 22 on placebo (FDA 2024) Trial
Muscle and joint pain Muscle pain in 14 of 43 vs 2 of 22; two people stopped for joint pain (FDA 2024) Trial
Higher blood sugar, lower insulin sensitivity Blood glucose rose in 15.4% vs 4.6%, HbA1c in 11.1% vs 1.4% (FDA 2024) Trial
Heart failure in frail older adults 4 of 62 (6.5%) vs 1 of 61 (1.7%); trial stopped early (Adunsky 2011) Trial
Higher blood pressure Systolic +11.9 to +16.4 mmHg vs little change on placebo in the same trial (FDA 2024) Trial
Raised liver enzymes Occasional, reversible; some stopped treatment; one 2025 case report (Cobani 2025) Trial, case report
Higher prolactin +23% but within normal range; a few women stopped for high prolactin (Chapman 1996, FDA 2024) Trial
Higher cortisol +47 nmol/L over 12 months; shorter trials saw no change (Nass 2008) Trial
Headache, tiredness, dizziness Reported in several trials; more often than placebo in the Alzheimer’s trial (FDA 2024) Trial
Cancer Not established. GH and IGF-1 drugs carry tumor warnings and long-term data are missing (FDA 2024) Not established

The full breakdown, including water retention, anxiety, cancer, testosterone and long-term use, is on our MK-677 side effects page. There are separate pages on gyno, headaches and hair.

MK-677, blood sugar and insulin

This is the most consistent safety finding across the trials. Growth hormone works against insulin, so raising GH tends to raise blood sugar.

  • In older adults, fasting glucose rose from 5.4 to 6.8 mmol/L (97 to 122 mg/dL) after four weeks on 25 mg/day (Chapman 1996).
  • Over 12 months, fasting glucose rose about 5 mg/dL, insulin sensitivity fell and HbA1c rose 0.2% (Nass 2008, FDA 2024).
  • In obese men, fasting glucose did not change but an oral glucose tolerance test got worse at 2 and 8 weeks (Svensson 1998).
  • In the 563-patient Alzheimer’s trial, blood glucose rose in 15.4% vs 4.6% on placebo and HbA1c in 11.1% vs 1.4% (FDA 2024).
  • In one 9-week study, 6% of participants had their dose cut from 25 to 10 mg because fasting glucose went above 140 mg/dL, and three of them still had to stop (FDA 2024).

Every glucose result from the trials is on our MK-677 and blood sugar page. Trial investigators watched fasting glucose, HbA1c and insulin for this reason. A 2022 case report described a 47-year-old with a history of metabolic syndrome who developed a hyperglycemic crisis after adding MK-677 and two SARMs (as summarized by the FDA 2024).

The heart-failure signal and the FDA’s Category 2 listing

In a Phase 2b trial, 123 adults aged 60 and over who were recovering from a hip fracture took 25 mg/day or placebo for 24 weeks. Congestive heart failure occurred in 4 of 62 people on MK-677 (6.5%) and 1 of 61 on placebo (1.7%). Blood pressure also rose: systolic pressure went up 11.9 to 16.4 mmHg on MK-677 and changed by +2.3 to −2.3 mmHg on placebo. The trial was stopped early, and the authors concluded that “MK-0677 has an unfavorable safety profile in this patient population” (Adunsky 2011, FDA 2024).

An earlier hip-fracture trial also found more edema and fluid overload on MK-677 (16 reports vs 10 on placebo) (FDA 2024).

Because of this signal, the FDA placed ibutamoren mesylate in Category 2 of bulk drug substances for compounding, the list of substances that “may present significant safety risks”. It has been there since 29 December 2022 for outsourcing facilities (503B) and since 29 September 2023 for compounding pharmacies (503A). The FDA’s reason: “Ibutamoren mesylate poses significant safety risks due to the potential for congestive heart failure in certain patients” (FDA Category 2 list).

These patients were old and frail, so the result does not show the same risk in a healthy 30-year-old. It does show that the fluid and blood pressure effects of MK-677 can matter, and no long-term heart study exists in younger people.

Does MK-677 lower testosterone? Do you need PCT?

MK-677 does not act on the androgen receptor, so it is not expected to shut down testosterone the way SARMs and steroids do. In one 8-week trial in obese men, total testosterone was lower than on placebo, but the testosterone/SHBG ratio (an index of free testosterone), LH and FSH did not change (Svensson 1999). No trial has tested MK-677 as post-cycle therapy. In a 2022 case report, a man taking LGD-4033 with MK-677 for five weeks still had total testosterone fall 62% (Cardaci 2022). More on this in MK-677 as PCT.

MK-677 dosage in studies

Adult trials used 2 to 50 mg once a day. 25 mg/day was the most common dose and the one used in every adult trial that lasted about 6 months or longer. Children with GH deficiency received weight-based doses of 0.2 to 3.2 mg/kg/day. IGF-1 rose with dose: in GH-deficient men, it rose 52% on 10 mg and 79% on 50 mg (Chapman 1997). Side effects such as high blood sugar led investigators to lower some people’s dose from 25 to 10 mg (FDA 2024). See MK-677 dosage for the full table, and MK-677 morning or night for the timing trials used.

MK-677 and sleep

MK-677 (ibutamoren) and sleep quality

Sleep is one of the most searched benefits. The evidence is one small 1997 study with bedtime dosing: 8 young adults had about 50% more stage IV (deep) sleep and over 20% more REM sleep on 25 mg than on placebo, and 6 older adults had nearly 50% more REM sleep (Copinschi 1997). In the 12-month trial, a combined well-being score that included a sleep-quality questionnaire did not differ from placebo (Nass 2008). So: a plausible effect, measured once, in very few people.

Can MK-677 increase height?

Only one group has been studied: young children with diagnosed GH deficiency, under medical care. They grew 6.0 to 8.2 cm a year on ibutamoren, faster than on placebo but slower than on injected GH (NCT04614337, FDA 2024). No trial has tested it in healthy teenagers or adults, and once growth plates close, bones stop lengthening (NIAMS). Details in MK-677 and height.

It depends on the country, and in most places the answer is “not as a medicine or supplement”:

  • US: not a controlled substance on the DEA list (DEA, October 2026), but not an approved drug either. In December 2025 the FDA called products sold as “MK-677 Ibutamoren” unapproved new drugs, despite “research use only” labels (FDA warning letter, 2025).
  • Australia: prescription-only (Schedule 4) and listed in Appendix D, clause 5: possession without authority is illegal (Poisons Standard, June 2026).
  • Germany: named in the Anti-Doping Act annex; buying or possessing non-small amounts for doping in sport is prohibited (AntiDopG).

The full country-by-country answer is in Is MK-677 legal?. For the SARMs side, see are SARMs legal.

Is MK-677 banned in sport? Does it show up on drug tests?

Yes. WADA prohibits ibutamoren (MK-677) at all times, in and out of competition, under S2.2.4 (WADA 2026). Anti-doping labs can find it at very low levels: a 2026 method detects sub-nanogram amounts in blood and dried blood spots (Mazzarino 2026), and a single 10 mg dose was still measurable in hair collected four weeks later (Kintz 2026). More on testing: WADA and testing and our SARMs drug test guide.

Bloodwork the trials tracked

These are the markers investigators measured, because they are where MK-677 caused problems. They are listed here as what the research watched, not as a testing plan.

  • IGF-1 (the main effect marker)
  • Fasting glucose, HbA1c and fasting insulin (blood sugar)
  • ALT and AST (liver enzymes)
  • Prolactin
  • Lipid panel
  • Blood pressure and swelling were also checked at visits

The PCT and bloodwork planner covers what each marker means.

What’s actually in products sold as MK-677?

Trials used pharmaceutical-grade drug. Products sold online are a different thing. When researchers bought 44 products sold as SARMs online, only 41% contained the amount on the label, 25% contained substances not on the label, and 39% contained a different unapproved drug instead of a SARM, ibutamoren among them (Van Wagoner 2017). In a five-year survey of 324 suspected illegal performance products analyzed by official medicines labs in 13 countries, ibutamoren topped the list of the five most reported molecules, and 24% of the products were sold as dietary supplements (Barrios 2025). In one case report, supplements labeled as MK-677, RAD-140 and cardarine also contained undeclared testosterone, estradiol and GH, and the man who took them developed breast growth and low testosterone (Chong 2024).

Even the certificates of analysis that the two nominators sent the FDA lacked data on chiral purity, impurities and residual solvents (FDA 2024). If you read a certificate, check that it is batch-specific and from an independent lab. Sarmguide’s current partner shop is SwissChems; our SwissChems review explains why.

MK-677 pros and cons

What the evidence supports What counts against it
Raises GH and IGF-1 when taken by mouth Raises blood sugar and lowers insulin sensitivity
Adds about 1 kg of fat-free mass over a year in older adults No gain in strength or physical function in trials
More deep and REM sleep in one small study Swelling, muscle and joint pain, more appetite
Less protein breakdown during a short diet Heart-failure signal and higher blood pressure in frail older adults
Small LDL drop Not approved anywhere; FDA Category 2; banned in sport
Long-acting: one dose covers about a day Products sold online often do not match their labels

MK-677 reviews: what users report vs what trials measured

Online, MK-677 is mostly used as a “lifestyle” drug. An expert interviewed for the University of Maryland (M-CERSI) report that the FDA cites said GH secretagogues are often taken to improve the look of skin, hair or body, frequently alongside testosterone (FDA 2024). User reviews, including the reader reports on our before-and-after page, tend to mention hunger, better sleep and water weight. Those match what trials measured. Claims about hair, skin, fat loss and strength are where reviews and trials part ways: the trials found no fat loss and no strength gain, and none tested hair or skin.

Tools: SARMs and peptides database · compare MK-677 with LGD-4033 · stack checker · WADA and testing · how we grade evidence.

Charts

Doses used in human studies of MK-677 What the published studies used and found. These are research doses reported in the studies, not recommendations. Dots mark each dose a study tested (per-kg doses are listed in the table only).
Doses used in human studies of MK-677Healthy adults aged 64–… (1996): 2–25 mg; Healthy young men (1996): 5–25 mg; 8 healthy adults aged 1… (1997): 5–25 mg; Healthy adults aged 24–… (1998): 25 mg; Obese men aged 18–50 (1998): 25 mg; Postmenopausal women ag… (2001): 25 mg; Adults aged 65 and over… (2004): 25 mg; Healthy adults aged 60–… (2008): 25 mg; Adults (2008): 25 mg; Older adults recovering… (2011): 25 mg; Adults (2018): 25 mg; Adults (2024): 25 mg; Men aged 17–34 (1997): 10–50 mg; Adults aged 65 and over (1999): 10–50 mg0 mg20 mg40 mg60 mgHealthy adults aged 64–… (1996)Healthy adults aged 64–… (1996): 2–25 mg2–25 mgHealthy young men (1996)Healthy young men (1996): 5–25 mg5–25 mg8 healthy adults aged 1… (1997)8 healthy adults aged 1… (1997): 5–25 mg5–25 mgHealthy adults aged 24–… (1998)Healthy adults aged 24–… (1998): 25 mg25 mgObese men aged 18–50 (1998)Obese men aged 18–50 (1998): 25 mg25 mgPostmenopausal women ag… (2001)Postmenopausal women ag… (2001): 25 mg25 mgAdults aged 65 and over… (2004)Adults aged 65 and over… (2004): 25 mg25 mgHealthy adults aged 60–… (2008)Healthy adults aged 60–… (2008): 25 mg25 mgAdults (2008)Adults (2008): 25 mg25 mgOlder adults recovering… (2011)Older adults recovering… (2011): 25 mg25 mgAdults (2018)Adults (2018): 25 mg25 mgAdults (2024)Adults (2024): 25 mg25 mgMen aged 17–34 (1997)Men aged 17–34 (1997): 10–50 mg10–50 mgAdults aged 65 and over (1999)Adults aged 65 and over (1999): 10–50 mg10–50 mg
Dose studiedWho took partDurationWhat the study foundSource
5 mg/day and 25 mg/day (bedtime)Healthy young men (n=9)7 days per periodRandomized, double-blind, 3-period crossover vs placebo IGF-1 rose with dose. GH pulses became more frequent. Cortisol levels over 24 hours did not change.PubMed 1996
2, 10 or 25 mg/dayHealthy adults aged 64–81 (n=32)28 daysRandomized, double-blind, placebo-controlled At 25 mg/day, mean 24-hour GH rose 97% at 2 weeks. IGF-1 rose from 141 to 265 µg/L at 4 weeks, into the young-adult range. Fasting glucose rose from 5.4 to 6.8 mmol/L.PubMed 1996
10 mg/day or 50 mg/dayMen aged 17–34 with severe childhood-onset GH deficiency (n=9)4 days per periodDouble-blind, rising-dose, placebo-controlled IGF-1 rose 52% on 10 mg and 79% on 50 mg. Fasting and after-meal insulin and after-meal glucose rose.PubMed 1997
5 and 25 mg/day (young); 2 then 25 mg/day (older)8 healthy adults aged 18–30 and 6 adults aged 65–71 (n=14)7 days (young); 14 days per period (older)Placebo-controlled crossover (young); two treatment periods (older) On 25 mg, young adults had about 50% more stage IV (deep) sleep and over 20% more REM sleep than on placebo. Older adults had nearly 50% more REM sleep.PubMed 1997
25 mg/dayHealthy adults aged 24–39 on a calorie-restricted diet (n=8)7 daysRandomized, double-blind, placebo-controlled crossover Nitrogen balance was +0.31 g/day on MK-677 vs −1.48 g/day on placebo, meaning less protein breakdown during dieting. IGF-1 rose.PubMed 1998
25 mg/dayObese men aged 18–50 (n=24)8 weeksRandomized, double-blind, placebo-controlled IGF-1 rose about 40%. Fat-free mass increased. Total and belly (visceral) fat did not change. An oral glucose tolerance test got worse.PubMed 1998
10, 25 or 50 mg/day across three trialsAdults aged 65 and over, healthy or with functional impairment (n=187)2–9 weeksThree randomized, double-blind, placebo-controlled trials IGF-1 rose 55–94%. Markers of bone formation and bone breakdown both rose.PubMed 1999
0.2 or 0.8 mg/kg/dayPrepubertal children with GH deficiency (n=18)7–8 daysRandomized, placebo-controlled, multicenter GH, IGF-1 and IGFBP-3 rose in some children. Glucose, insulin, thyroid hormones and cortisol did not change.PubMed 2001
25 mg/day, alone or with alendronate 10 mg/dayPostmenopausal women aged 64–85 with low hip bone density (n=292)12 months (bone density to 18 months)Randomized, double-blind, placebo-controlled, multicenter IGF-1 rose 39–45%. With alendronate, femoral-neck bone density rose 4.2% vs 2.5% on alendronate alone. There was no extra gain at the spine, total hip or whole body.PubMed 2001
25 mg/dayAdults aged 65 and over recovering from hip fracture (n=161)6 monthsRandomized, double-blind, placebo-controlled, 13 centers IGF-1 rose 84% vs 17% on placebo. Physical function did not differ significantly from placebo.PubMed 2004
25 mg/dayHealthy adults aged 60–81 (n=65)12 months (plus a 12-month extension)Randomized, double-blind, placebo-controlled, modified crossover GH rose 1.8-fold and IGF-1 1.5-fold. Fat-free mass rose 1.1 kg vs a 0.5 kg loss on placebo. Strength and physical function did not change. Fasting glucose rose about 5 mg/dL.PubMed 2008
25 mg/dayAdults with mild to moderate Alzheimer's disease (n=563)12 monthsRandomized, double-blind, placebo-controlled, multicenter IGF-1 rose 72.9% at 12 months. There was no effect on the progression of Alzheimer's disease.PubMed 2008
25 mg/dayOlder adults recovering from hip fracture (n=123)24 weeksRandomized, double-blind, placebo-controlled, multicenter Phase 2b IGF-1 rose 51.4 ng/mL more than placebo. Gait speed improved a little, but most function tests did not. The trial was stopped early because of a heart-failure safety signal.PubMed 2011
25 mg/day (per the trial registry, NCT00395291)Adults on hemodialysis (n=26)About 30 days per periodRandomized, blinded, placebo-controlled crossover 22 people finished. IGF-1 rose 65% more on MK-0677 than on placebo. No serious side effects were linked to the drug.PubMed 2018
0.4 or 0.8 mg/kg/dayPrepubertal children with GH deficiency (trial run 1996–1998) (n=68)6 monthsRandomized, double-blind, placebo-controlled Height velocity was 6.0 and 6.9 cm/year on the two doses vs 4.5 cm/year on placebo and 11.1 cm/year on injected growth hormone. Increased appetite was the most common drug-related side effect.fda.gov 2024
0.8, 1.6 or 3.2 mg/kg/day (as LUM-201)Prepubertal children with GH deficiency who passed a screening test (n=104)6 months (primary result; 24-month study)Randomized, open-label Phase 2 vs injected growth hormone (OraGrowtH210) Annualized height velocity was 6.8, 8.2 and 7.7 cm/year on the three doses vs 10.6 cm/year on injected growth hormone (80 children in these arms).clinicaltrials.gov 2024
25 mg/day (as LUM-201)Adults with overweight or obesity and fatty liver disease (NAFLD) (n=12)6 monthsOpen-label pilot, no placebo Liver fat did not fall: it changed by +3.9 percentage points on average (not significant, 7 people analyzed). ALT did not change significantly.clinicaltrials.gov 2024

Sources: the studies linked in the table.

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Half-life of MK-677 compared Elimination half-life in people, where measured (log scale; bars show the reported range). Values from different studies and routes are not directly comparable.
Half-life of MK-677 comparedIpamorelin: ~2 h; Enclomiphene: ~8–10 h; Clomiphene: ~5–24 h (No single value: enclomiphene part ~5–10 h; zuclomiphene part ~24 h with a very long tail (detectable for over a month)); Ostarine: ~14–24 h; LGD-4033: ~24–36 h (24–36 h); RAD-140: ~45 h; Anastrozole: ~2–2.1 days (~50 h); Tamoxifen: ~5–7 days (~5–7 days (tamoxifen); ~14 days (N-desmethyltamoxifen, main active metabolite)); CJC-1295: ~5.8–8.1 days (~6–8 days); MK-677: not established1 h3 h6 h12 h1 day3 days1 weekIpamorelinIpamorelin: ~2 h~2 hEnclomipheneEnclomiphene: ~8–10 h~8–10 hClomipheneClomiphene: ~5–24 h (No single value: enclomiphene part ~5–10 h; zuclomiphene part ~24 h with a very long tail (detectable for over a month))~5–24 hOstarineOstarine: ~14–24 h~14–24 hLGD-4033LGD-4033: ~24–36 h (24–36 h)~24–36 hRAD-140RAD-140: ~45 h~45 hAnastrozoleAnastrozole: ~2–2.1 days (~50 h)~2–2.1 daysTamoxifenTamoxifen: ~5–7 days (~5–7 days (tamoxifen); ~14 days (N-desmethyltamoxifen, main active metabolite))~5–7 daysCJC-1295CJC-1295: ~5.8–8.1 days (~6–8 days)~5.8–8.1 daysMK-677not established

Source: Sarmguide compound database; MK-677 value: FDA Briefing Document, Pharmacy Compounding Advisory Committee, 29 October 2024: Ibutamoren Mesylate (2024).

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More on MK-677

Frequently asked questions

Is MK-677 a SARM?

NoEvidence: Law

MK-677 is a growth hormone secretagogue: it copies ghrelin and makes the pituitary release more growth hormone, while SARMs act on the androgen receptor. The FDA states that MK-677 is a GHS, not a SARM.

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Is MK-677 safe?

Not shown to be safeEvidence: Trial

Blood sugar rose in trials, some people needed a lower dose or had to stop, and a trial in frail older adults was stopped early because of heart failure. The FDA lists ibutamoren among substances that may present significant safety risks.

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Is MK-677 legal?

Not approved anywhereEvidence: Law

In the US it is not a controlled substance, but the FDA treats products sold as MK-677 as unapproved new drugs. In Australia it is prescription-only and possession without authority is illegal; WADA bans it in sport.

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What does MK-677 do?

Raises GH and IGF-1Evidence: Trial

In a 12-month trial in adults aged 60 to 81, 25 mg/day raised IGF-1 1.5-fold and added 1.1 kg of fat-free mass and 2.7 kg of body weight. Strength, belly fat and total fat did not change.

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How long does MK-677 take to work?

IGF-1 rises within weeksEvidence: Trial

In older adults on 25 mg/day, IGF-1 went from 141 to 219 µg/L at 2 weeks and 265 µg/L at 4 weeks. Body composition changes in trials were measured over 8 weeks to 12 months.

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What is the half-life of MK-677?

Not published for humansEvidence: Human data

The FDA found no detailed human pharmacokinetic data in 2024. One dose raises growth hormone for about 24 hours; vendor half-life figures are not backed by a published human study.

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Does MK-677 raise blood sugar?

YesEvidence: Trial

In the Alzheimer's trial, blood glucose rose in 15.4% of patients vs 4.6% on placebo, and HbA1c in 11.1% vs 1.4%. Some participants had their dose lowered or stopped because of high glucose.

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Does MK-677 lower testosterone or need PCT?

Not a direct suppressorEvidence: Trial

In one 8-week trial, total testosterone was lower than on placebo, but the testosterone/SHBG ratio, LH and FSH did not change. No trial has tested it as post-cycle therapy, and with LGD-4033 in one case report it did not prevent a 62% testosterone drop.

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Does MK-677 cause gyno?

Not shown in trialsEvidence: Trial

Gynecomastia does not appear in the trial safety data the FDA reviewed, though rises in prolactin, weight and water can look like gyno. The best-documented case involved products that also contained hidden hormones.

Does MK-677 improve sleep?

Possibly; one small studyEvidence: Trial

In a 1997 study, young adults on 25 mg at bedtime had about 50% more deep sleep and over 20% more REM sleep than on placebo. The study had 14 people and lasted 1 to 2 weeks.

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Does MK-677 show up on a drug test?

Yes, in sport testingEvidence: Law

WADA bans it at all times, and anti-doping labs can detect it in blood at sub-nanogram levels. In a 2026 study a single 10 mg dose was still found in hair collected four weeks later.

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Can MK-677 increase height?

Only shown in GH-deficient kidsEvidence: Trial

It sped up growth in young children with diagnosed growth hormone deficiency, less than GH injections did. No trial has tested it in healthy teenagers or adults, and after the growth plates close bones stop lengthening.

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Sources

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