Reference

Last reviewed: 29 Apr 2026
Sources cited: 11

Compound class528.66 g/mol (free base); 624.76 g/mol (mesylate salt)

Orally-active non-peptide ghrelin-receptor agonist (small-molecule peptidomimetic, not a peptide)

Small molecule (528.66 g/mol; mesylate salt 624.76 g/mol) designed by Merck as the first published peptidomimetic drug. Binds the same GHSR-1a receptor as ipamorelin and ghrelin but with no peptide bonds — chemically a substituted spiropiperidine derivative. The 24-hour plasma half-life and oral bioavailability come from the non-peptide structure resisting GI peptidases.

MK-677 (Ibutamoren)

Last verified: 2026-04-29

At a glance


Also known as	Ibutamoren, MK-0677, L-163,191, LUM-201, Nutrobal (research-chem trade name), Oratrope
Class	Orally-active non-peptide ghrelin-receptor agonist (peptidomimetic small molecule)
Typical route	Oral (capsule, liquid, or research-chem powder)
Half-life	~24 hours; peak serum 2–3 hours post-dose; once-daily dosing produces sustained 24-hour GH/IGF-1 elevation1 2
Molecular weight	528.66 g/mol (mesylate salt: 624.76 g/mol)
Sequence / structure	Not a peptide. A small-molecule peptidomimetic — Merck’s first published peptidomimetic drug — designed to mimic GHRP-6 receptor binding without peptide bonds.
UK status	Not approved as a medicine. Sold as a research chemical; supplying for human consumption is unlawful under the Psychoactive Substances Act 2016.
US status	Not FDA-approved for any indication. Not controlled by DEA. Sold as a research chemical labelled “not for human consumption.” Listed by FDA as a substance posing “significant safety risks due to the potential for congestive heart failure in certain patients.”7

What it is

MK-677 is the GH-secretagogue cluster’s outlier in three ways: it is orally active, it is not a peptide, and its clinical development was terminated in late-stage trials due to a cardiac safety signal. It mimics the action of ipamorelin pharmacologically — both are agonists at the ghrelin receptor (GHSR-1a) — but where ipamorelin is a 5-residue peptide that requires injection, MK-677 is a small molecule with a 24-hour half-life that survives the gastrointestinal tract and produces sustained GH and IGF-1 elevation for over a day from a single oral dose.

It was developed by Merck in the 1990s as the first published peptidomimetic drug. Merck pursued multiple indications — paediatric growth hormone deficiency, adult-onset GHD, sarcopenia, frailty in older adults, and most consequentially, recovery from hip fracture in elderly patients. The hip fracture Phase IIb trial (Adunsky et al.) found a higher rate of congestive heart failure in the MK-677 group (6.5% vs 1.7% placebo), leading to early trial termination.3 Merck discontinued the development program in the late 2000s.

The biohacker community uses MK-677 off-label for body composition, sleep architecture, and recovery — the same use cases as the GHRP cluster — at the dose Merck studied in healthy older adults: 25 mg orally once daily. The pharmacology supports the use; the cardiac safety signal that ended Merck’s program applies here too, especially for users with cardiovascular risk factors or in extended use beyond what the trials documented.

It is not human growth hormone. Like the rest of the GH cluster, MK-677 asks the pituitary to release more of its own GH; it doesn’t replace GH. Unlike the rest of the cluster, the GH elevation is sustained over 24 hours rather than pulsatile.

Mechanism

MK-677 is a non-peptide agonist of the growth hormone secretagogue receptor type 1a (GHSR-1a) — the ghrelin receptor — the same target as ipamorelin and the older GHRPs (GHRP-2, GHRP-6, hexarelin).1 5

The mechanism distinguishes MK-677 from the rest of the cluster in three ways:

Sustained GH elevation rather than pulsatile. A single 25 mg oral dose produces measurable GH elevation for over 24 hours and meaningful IGF-1 elevation for days. Unlike ipamorelin (which produces a discrete pulse that resolves in hours), MK-677 maintains continuous GHSR-1a stimulation. The effect is closer to CJC-1295 with DAC than to ipamorelin or sermorelin.
Multi-pathway action. Beyond direct GHSR-1a agonism, MK-677 has documented effects on (a) GHRH release from the hypothalamus, (b) suppression of somatostatin tone, and (c) potentiation of GHRH signalling at the pituitary. The net effect is broader GH-axis activation than a single-receptor agonist would produce.
Oral bioavailability. As a small molecule, MK-677 survives gastric acid and intestinal peptidases that would degrade any peptide GHRP. This is why the rest of the GHRP cluster requires injection and MK-677 doesn’t.

The downstream cascade is the same as the rest of the cluster: GHSR-1a activation → GH release → hepatic IGF-1 production. Trial data documented sustained IGF-1 elevation over 12–24 month dosing periods in older adults — the same biomarker the GHRP and GHRH compounds elevate, achieved through a different molecular route.

The mechanistic concern with the sustained-elevation pattern is the same as for CJC-1295 with DAC: the body’s natural pulsatile GH rhythm is replaced with continuous low-amplitude stimulation, and the consequences of that pattern over months-to-years of use are not fully characterised.

Routes of administration

Oral (the standard and only viable route)


Bioavailability	Sufficient for sustained 24-hour GH/IGF-1 elevation; exact figure not published in standard sources
Onset	Peak serum 2–3 hours post-dose; GH elevation begins within 1 hour
Duration	24-hour GH elevation per single dose; daily dosing produces continuous IGF-1 elevation at steady state (3–4 weeks)
Typical dose (this route)	12.5–25 mg once daily, taken at bedtime
Equipment	None required beyond the capsule, liquid dropper, or weighing scale (depending on supply form)
When this route makes sense	Default. The compound was designed for oral activity; no other route is studied or used.

Bedtime dosing is the community-standard convention because the ghrelin-receptor agonism produces a noticeable hunger spike in many users; taking the dose before sleep means hunger arrives during the sleep window when it’s easier to ignore. The hunger effect is typically most prominent in the first 1–2 weeks of use and attenuates with continued dosing.

Sublingual


Bioavailability	Not formally characterised; some research-chem vendors supply sublingual liquid formulations with the implicit claim that absorption is faster
When this route makes sense	Rarely used in practice. The 24-hour half-life and GI-stable molecular structure mean oral and sublingual produce indistinguishable end-states for most users.

Injectable, intranasal

Not used. MK-677 was designed for oral delivery; no peer-reviewed data exists for any injection or intranasal route. Some research-chem vendors sell injectable preparations of MK-677 mesylate but these have no advantage over oral and introduce sterility concerns the oral route doesn’t have.

Cross-route comparison

Oral is the only meaningful route. All clinical data, all community use, and the entire pharmaceutical development program ran on oral once-daily dosing. The route question for MK-677 is timing (typically bedtime) and form (capsule vs liquid vs research-chem powder), not which route to use.

What the evidence says

Honest summary: MK-677 has the strongest pharmacokinetic and short-term efficacy data of any GH-secretagogue compound — it does what it claims to do, oral once-daily, with sustained GH and IGF-1 elevation over 12–24 months in healthy older adults. The clinical development program was terminated due to a congestive heart failure signal in elderly hip-fracture patients, and that safety signal has not been re-examined under controlled conditions in any subsequent registrational program.

Healthy older adult trials (the strongest published efficacy data)

The Nass et al. 2008 trial gave 25 mg daily MK-677 to healthy adults over 60 for two years.6 10 Outcomes:

Sustained GH and IGF-1 elevation over the 2-year duration
Increases in lean body mass (~2.7 lbs over baseline)
No measurable change in muscle strength or functional outcomes (this is the negative finding that matters — the body composition changed, the function didn’t)
Persistent fluid retention and modest insulin resistance
Two participants developed congestive heart failure during the trial, with the safety signal becoming a defining feature of MK-677’s clinical record

The “lean mass goes up but function doesn’t change” finding is consistent across the broader GH literature — sustained GH elevation produces measurable body-composition shifts that don’t translate to corresponding functional improvements in older adults.

Adunsky 2011 hip-fracture trial (the trial that ended development)

Phase IIb in elderly patients recovering from hip fracture. CHF rate 6.5% in MK-677 group vs 1.7% in placebo. The trial was terminated early. This is the safety signal that ended Merck’s clinical development program; no Phase 3 has been brought forward by any sponsor since.3

The interpretive question is whether the CHF signal generalises beyond the elderly hip-fracture population. The trial population was enriched for cardiovascular risk by definition (frailty, post-surgical state, advanced age). The mechanism — GH-driven sodium and water retention combined with IGF-1-mediated cardiac effects — is plausible enough that the signal cannot be safely dismissed as population-specific without controlled data in healthier populations.

For users with no cardiovascular risk factors, the absolute risk in the trial population (6.5% over the trial duration) probably overstates the risk in healthier biohacker users. For users with any cardiovascular risk factors — hypertension, prior MI, family history of premature CHD, diabetes — the signal is too clear to ignore.

Insulin resistance signal

Trials at 25 mg/day consistently document rising fasting glucose and declining insulin sensitivity over 12–24 month dosing periods.6 The effect is mechanistically expected (GH antagonises insulin) and dose-related. For users with no baseline insulin issues this typically returns toward baseline after stopping; for users with prediabetes or T2D it can meaningfully accelerate glycaemic deterioration.

What the evidence does NOT show

No outcome trials in healthy biohacker populations at typical community use durations.
No body-composition outcome data beyond the lean-mass-up-without-function-change finding in older adults.
No characterisation of MK-677’s CHF signal in non-elderly populations — the trial that flagged it was in 60+ post-hip-fracture patients.
No long-term cancer outcome data — IGF-1 elevation is sustained at 24-hour cycle; the theoretical mitogenicity concern is not directly studied.
No comparative trials of MK-677 vs ipamorelin, CJC-1295, or HGH at any controlled level.

The compound’s pharmacology is well-characterised; the cardiac and metabolic safety signals are documented; the long-term clinical risk-benefit picture is genuinely uncharacterised in the populations most likely to use it.

Typical use patterns

Standard biohacker protocol

The community-standard pattern follows the dose Merck used in the Nass 2008 trial:

25 mg orally once daily, at bedtime
Cycles of 8–16 weeks on, with breaks of 4–8 weeks
Some users run continuously for 6+ months; others stay strictly within shorter cycles for receptor-sensitivity and side-effect-management reasons

Lower-dose protocols at 12.5 mg (half-cap) are increasingly common, particularly among users who experienced significant water retention or appetite spike at 25 mg. The dose-response curve flattens above 25 mg in the published data — going higher is not generally productive.

Sensitive-start protocol

For users new to MK-677 or with reactive systems:

10–12.5 mg daily for 2–4 weeks
Hold before considering a step to 25 mg
Many sensitive users find 12.5 mg sufficient and never need to escalate

Cycling

The community 8-on / 8-off (or longer breaks) convention serves two purposes: (a) GHSR-1a desensitisation precaution, theoretically; (b) insulin sensitivity recovery during the off-cycle, which is the more practically important one. Continuous 12-month dosing produced measurable insulin-resistance effects in the trial data; cycling protocols are designed to give the metabolic system periodic recovery windows.

Stacking

Other GHRPs (ipamorelin, GHRP-2, GHRP-6, hexarelin): redundant — same receptor. Adding ipamorelin to MK-677 does not produce the synergy ipamorelin produces with CJC-1295 because the GHSR-1a is already sustainably occupied.
GHRH analogues (CJC-1295, sermorelin, tesamorelin): mechanistically synergistic. Combining MK-677 (GHSR-1a) with a GHRH analogue (GHRH-R) hits both receptors. The synergy is theoretical; not directly studied.
HGH: redundant.
GLP-1 agonists (semaglutide, tirzepatide): common pairing in the metabolic-optimisation crowd. Worth specific caution — both compounds independently affect glucose handling and the net effect on insulin sensitivity over months is not predictable. Users on this stack should monitor fasting glucose and HbA1c more closely than for either compound alone.
BPC-157 / TB-500: common during recovery phases. No documented interactions.
NAD+ precursors, MOTS-c: common in longevity stacks. No documented interactions.

Why a user would choose MK-677 over the injectable GH cluster

Oral. No injections. The biggest practical difference.
Sustained 24-hour elevation rather than discrete pulses.
Cost is generally lower than the compounded or research-chem injectable peptides per month of treatment.
Convenience. Once-daily oral capsule is dramatically easier to maintain protocol adherence on than daily subQ injections.

Why a user would choose injectable GH peptides over MK-677

Pulsatile pattern matches natural GH rhythm — argued to be more physiologically appropriate, especially long-term.
Smaller per-day exposure to GH/IGF-1 elevation given the on-off pulse pattern.
No CHF safety signal of the kind MK-677 carries from the Adunsky 2011 trial.
No oral metabolism through CYP3A4 — relevant for users on medications that affect that enzyme.

For sensitive systems

MK-677’s profile in sensitive-systems users diverges from the rest of the GH cluster in two important ways: the GH/IGF-1 elevation is sustained over 24 hours rather than pulsatile, and the CHF safety signal from the Adunsky trial means cardiovascular risk factors carry more weight here than for ipamorelin or sermorelin.

Start dose for sensitive users. 10–12.5 mg orally at bedtime. Hold for 3–4 weeks before considering any increase. Many sensitive users do not benefit from going above 12.5 mg.

Ramp. If tolerated, 25 mg is the upper community-standard dose; the dose-response curve flattens above this. There is no benefit to higher doses and the side-effect profile worsens.

Expected adjustment profile:

Hunger spike in the first 1–2 weeks — the most universally reported MK-677 effect. Ghrelin-receptor agonism drives appetite. Usually attenuates with continued dosing but doesn’t fully disappear. Bedtime dosing minimises the disruption.
Vivid dreaming and lucid dreams — common across the GH cluster but most pronounced with MK-677 because of the sustained nighttime elevation.
Mild lower-extremity oedema — fluid retention from GH-driven sodium and water retention. Documented in the trial data; reverses with dose reduction or discontinuation.
Carpal-tunnel-like numbness or tingling in hands and wrists — same fluid-retention mechanism as the injectable GH cluster.
Lethargy or mild fatigue in the first 1–2 weeks, particularly morning fatigue — likely related to fluid shifts; usually resolves.
Mild flushing or warmth after dosing — transient.

What’s not normal and warrants stopping: persistent oedema that doesn’t reverse on dose reduction, dyspnoea (shortness of breath) on exertion or lying flat, lower-extremity swelling that’s bilateral and progressive, atypical chest sensations, palpitations, blood-pressure elevation, glucose dysregulation in users tracking it. The CHF signal from the Adunsky trial means these symptoms are not “wait and see” — they’re stop-and-reassess signals, especially in users with any cardiovascular history or risk factors.

For MCAS / histamine-sensitive users. No specific histamine activity documented. The receptor target is not directly mast-cell-relevant. The hunger spike is the most-noticed effect and is mechanism-driven, not allergic.

For POTS users. Sustained fluid retention is the most relevant concern. POTS users typically have already-altered fluid balance; adding sustained sodium/water retention can worsen orthostatic symptoms or, paradoxically, mask them temporarily by raising blood volume. Worth monitoring HR and orthostatic readings carefully in the first 4 weeks; consider sensitive-start dosing at 10 mg.

For UARS / chronic fatigue / ME/CFS. MK-677 is the GH-cluster compound most likely to produce a noticeable subjective sleep change because of the sustained nighttime GH elevation — vivid dreams, deeper slow-wave sleep are common reports. Worth a 4-week trial. The hunger effect can be a problem for users whose ME/CFS profile includes appetite dysregulation; monitor weight and food intake patterns.

For active or recent cancer history. Relative contraindication, slightly stronger framing than for the rest of the GH cluster. MK-677’s sustained 24-hour IGF-1 elevation produces continuous mitogenic signalling that the pulsatile GHRP/GHRH alternatives don’t. Treat as a relative contraindication for active malignancy, recent (within ~5 years) malignancy of GH/IGF-1-responsive types — breast, prostate, colon, certain endocrine tumours — MEN syndromes, and strong family history without active screening.

For diabetes (especially type 2) or prediabetes. Special caution. The insulin resistance signal in the trial data is consistent and dose-dependent. Users with prediabetes or active T2D run measurably worse glycaemic control on MK-677. Either monitor fasting glucose and HbA1c closely (every 8–12 weeks), titrate diabetes medication accordingly with prescriber input, or choose a different compound.

For cardiovascular risk. Relative contraindication for users with significant CV risk factors. Hypertension, prior MI, family history of premature CHD, age over 65, frailty, prior heart failure of any kind — the Adunsky CHF signal is most directly relevant here. The trial population that flagged the signal was elderly post-hip-fracture; the mechanism (GH-driven fluid retention plus IGF-1 cardiac effects) is not population-specific. Users with cardiovascular concerns should treat MK-677 as a relative contraindication in the absence of cardiac workup.

Interactions worth considering:

HGH: redundant.
Other GHSR-1a agonists (ipamorelin, GHRP-2/6, hexarelin): redundant.
GHRH analogues: mechanistically synergistic; not studied for safety in combination.
Insulin / metformin / GLP-1 agonists: monitor glucose closely. GH antagonises insulin; the combined effect with GLP-1 agonists is not well-characterised.
CYP3A4-affecting medications (azole antifungals, macrolides, grapefruit, many SSRIs, statins, calcium-channel blockers, etc.): MK-677 is metabolised primarily through CYP3A4. Strong CYP3A4 inhibitors will increase MK-677 exposure; inducers will decrease it. This is the only compound in the GH cluster where prescription-medication interactions are mediated through a hepatic enzyme rather than a direct hormonal effect.
Steroids: corticosteroids blunt GH-axis response; reduce MK-677 efficacy.
SSRIs, SNRIs, LDN, beta-blockers: no documented direct interactions, but check the CYP3A4 picture for any specific medication.

Reasonable expectations

Onset. Subjective effects — appetite increase, vivid dreams, deeper sleep — are typically noticed within the first 1–2 weeks. IGF-1 elevation is measurable from the first week. Body composition changes, where they occur, take 8–16 weeks of consistent dosing.

Response rate. Sleep quality and dream vividness are the most consistently reported subjective effects across community use. Body-composition response is more variable and the published trial data showed lean-mass increase without functional improvement — which is to say, the scale changes but the workout numbers may not.

What the evidence actually supports.

Sustained GH and IGF-1 elevation with daily oral dosing — strongly supported.
Modest lean-mass increase in healthy older adults over 12–24 months — supported.
Increased appetite and food intake — supported.

What the evidence does not support.

Functional or strength outcomes — the Nass 2008 trial specifically showed lean mass up without functional change.
Hip fracture recovery — the Adunsky 2011 trial failed for this indication on safety grounds.
Body composition outcomes in healthy biohackers at any specific magnitude — not directly studied.
Anti-ageing or longevity outcomes — speculative.

What not to expect.

HGH-equivalent body composition effects in any time frame.
Strength or athletic-performance gains — the trial data is consistent that lean mass and function are decoupled with this compound.
A clean side-effect profile. Hunger, fluid retention, and insulin resistance are the documented effects, not edge cases.

Cost

MK-677 is not available through licensed pharmacy channels in the UK or US. No prescription pathway, no compounding-pharmacy access (unlike sermorelin), no NHS or insurance-supported route.

Research-chemical / SARMs vendor market

MK-677 is sold primarily through SARMs and research-chem vendors rather than peptide-specific vendors. Common forms:

Capsules (10 mg or 25 mg per cap) — the most common consumer form
Liquid suspension (typically 25 mg/mL in flavoured carrier)
Bulk powder (mesylate salt, requires accurate weighing)

Approximate UK market pricing:

30 capsules at 25 mg: ~£25–60
30 mL liquid at 25 mg/mL: ~£20–50
1 g powder: ~£40–90

Monthly cost at 25 mg/day: roughly £20–50/month, the cheapest GH-cluster compound by a meaningful margin. The oral form means no syringes, no BAC water, no injection-supply costs.

Sensitive-start economics. A user starting at 12.5 mg daily uses half the capsule (often easier with liquid form, where 0.5 mL = 12.5 mg) and runs vials twice as long.

Quality variance

The SARMs/research-chem vendor space has documented quality issues with MK-677 specifically:

Underdosed product (capsules containing less than labelled)
No active ingredient (some products tested at zero MK-677 content)
Substituted ingredients — cases of products labelled MK-677 that contained other compounds entirely

Lab-tested vendors with explicit third-party mass-spec or HPLC certificates are the meaningful quality signal. Buying from vendors who only sell SARMs and have no peptide presence raises the variance further than the broader peptide market.

Reconstitution

MK-677 is a small molecule, not a peptide. It does not require reconstitution. This is a meaningful practical advantage over the rest of the GH cluster: no BAC water, no syringes, no 7-to-28-day stability windows, no cold-chain requirements.

Capsule form: swallow with water. Bedtime is the community-standard timing.

Liquid form: measured by dropper. The supplier’s label specifies mg per mL; measure carefully. Liquid form is most useful for low-dose protocols (e.g. 12.5 mg = 0.5 mL of a 25 mg/mL liquid) and for users who want sub-25 mg dose precision.

Bulk powder form: requires weighing on an accurate milligram scale. Do not eyeball doses of MK-677 powder. The therapeutic range (10–25 mg) is narrow enough that a 50% weighing error materially changes the side-effect profile. Bulk powder is the cheapest per-mg route but has the highest dosing-error risk; capsules or liquid are safer for most users.

Storage

Capsules, sealed bottle: room temperature, away from heat and direct light. Manufacturer expiry dates apply.
Liquid suspension, sealed bottle: room temperature; refrigerate after first opening. Most vendors quote 6–12 months of shelf life sealed.
Bulk powder: sealed, dry, room temperature. MK-677 mesylate is hygroscopic; store in a dry environment, preferably with desiccant.

What gets miscalculated

Confusing MK-677 dose units with peptide dose units. MK-677 is dosed in mg (10–25 mg). Users coming from ipamorelin (mcg) or other peptide compounds sometimes underdose or overdose by 1000× through unit confusion.
Eyeballing bulk-powder doses. Without an accurate scale, dose precision is impossible. Capsules or pre-formulated liquid are safer.
Stacking with other GHSR-1a agonists. Adding ipamorelin to MK-677 doesn’t produce additive effect because the receptor is already sustainably occupied.
Skipping cycling and assuming insulin sensitivity will hold. The trial data shows insulin sensitivity declines with continuous dosing. Users who run MK-677 indefinitely without breaks accumulate metabolic risk that doesn’t show up in subjective symptoms early.
Treating MK-677 as a “lower-risk alternative to injectable GH peptides.” The CHF signal and insulin resistance signal in the trial data make it arguably higher-risk than ipamorelin or sermorelin for the populations where those signals matter.

Areas of concern ⚠

The CHF signal from the Adunsky 2011 trial

Phase IIb in elderly hip-fracture patients showed CHF rates 6.5% in MK-677 group vs 1.7% placebo, leading to early trial termination. Merck discontinued development; no Phase 3 has been brought forward by any sponsor since.3 7 The cardiac signal is what ended a 20-year-old clinical program — and its mechanism (GH-driven fluid retention plus IGF-1-mediated cardiac effects) doesn’t have a clear “this only applied to that population” boundary.

The trial population was high-risk by definition (frailty, post-surgical, advanced age). The signal may not generalise to healthy biohacker populations at the same rate. But the mechanism — sustained GH-driven fluid retention plus IGF-1-mediated cardiac effects — is not population-specific, and the absence of follow-up trials in healthier populations means the question has not been resolved under controlled conditions.

For users with cardiovascular risk factors, MK-677 should be treated as a relative contraindication in the absence of cardiac workup.

The insulin resistance signal

Trials at 25 mg/day consistently document rising fasting glucose and declining insulin sensitivity over 12–24 month dosing periods.6 The effect is mechanistically expected and dose-related. Continuous dosing without breaks accumulates metabolic risk. Users with prediabetes or T2D should not use MK-677 without prescriber-supervised glucose monitoring. Cycling protocols are designed in part to allow insulin-sensitivity recovery during off-periods.

Cancer / IGF-1 / GH-axis concern (sustained elevation amplifies the concern)

Same framing as the rest of the GH cluster, with the specific MK-677 caveat: the IGF-1 elevation is sustained over 24 hours rather than pulsatile, which means continuous mitogenic signalling rather than discrete spikes. The theoretical concern about GH/IGF-1-responsive tumour growth is amplified by the elevation pattern.

Treat as a relative contraindication for:

Active malignancy of any type
Recent (within ~5 years) malignancy of GH/IGF-1-responsive types — breast, prostate, colon, certain endocrine tumours
Multiple Endocrine Neoplasia syndromes
Strong family history of GH/IGF-1-responsive cancers without active screening in place

The FDA’s listing of MK-677 as posing “significant safety risks due to the potential for congestive heart failure in certain patients” is a regulatory stance that compounds the cancer concern editorially — the agency has flagged this compound on safety grounds, not just on approval-status grounds.

Quality and sourcing — variance higher than the peptide market

MK-677 sits in the SARMs/research-chem vendor space rather than the peptide vendor space. Documented issues include underdosing, zero-ingredient products, and substituted ingredients. Lab-tested vendors with mass-spec or HPLC certificates are the meaningful quality marker. Capsules from vendors with no chemistry transparency are the highest-variance form; powder from lab-tested vendors with certificates is the lowest-variance but requires weighing accuracy.

Long-term safety beyond ~24 months is uncharacterised

The longest controlled human trial is approximately 24 months in older adults. Multi-year safety in healthy biohacker populations is unknown. Mechanistic concerns:

IGF-1 elevation is sustained, theoretically continuous mitogenic signalling
Insulin sensitivity declines with continuous dosing
Pituitary feedback over months-to-years is not characterised
Cardiac effects beyond the Adunsky signal are not characterised in non-elderly populations

Populations where MK-677 is contraindicated or high-risk

Active or recent cancer history (relative contraindication; see above)
Active or significant cardiovascular disease — special concern; relative contraindication without workup
Diabetes (type 1 or poorly-controlled type 2) — insulin resistance signal makes glycaemic management harder
Active acromegaly or known pituitary adenoma
Pregnancy and breastfeeding — no safety data
Under 18 — endogenous GH is already at peak; no use case
Sleep apnoea (untreated) — GH/IGF-1 effects on soft tissue may worsen airway collapse
Severe insulin resistance or metabolic syndrome — same concern as diabetes
Patients on strong CYP3A4 inhibitors or inducers — drug-interaction risk through hepatic metabolism

Measurement and dosing pitfalls

mg vs mcg confusion — MK-677 is dosed in mg, not mcg. Users transitioning from peptide compounds make this error. 25 mg ≠ 25 mcg by 1000×.
Eyeballing powder doses — therapeutic range is 10–25 mg; weighing accuracy matters.
Skipping cycling — insulin resistance accumulates with continuous dosing.
Assuming oral means low-risk — the CHF and insulin resistance signals are documented; oral delivery doesn’t eliminate them.
Stacking with GHRPs expecting additive GH pulse — same receptor; not additive.

What the community gets wrong

“Oral SARMs alternative for cutting.” MK-677 is not a SARM (it’s not a selective androgen receptor modulator), and it doesn’t preferentially drive cutting outcomes — it drives lean-mass increase with documented water retention and insulin resistance, which is the opposite of “cutting” for body-composition purposes.
“Safer than HGH because it’s not HGH.” The CHF signal and insulin resistance signal are real and documented in trial data; HGH at therapeutic doses has its own profile but MK-677 is not a uniformly safer alternative.
“No side effects at low dose.” Hunger, vivid dreams, mild fluid retention, and modest insulin sensitivity changes are all dose-dependent but not dose-eliminable. Even 12.5 mg produces measurable IGF-1 elevation and the associated effects.
“FDA hasn’t banned it so it’s fine.” The FDA has explicitly flagged MK-677 as posing significant safety risks. Not-banned and safe are not the same regulatory position.

FDA / regulatory status

Jurisdiction	Status	Last verified
US (FDA)	Not approved. Listed by FDA as a substance posing “significant safety risks due to the potential for congestive heart failure in certain patients.” Not DEA-controlled. Sold as a research chemical labelled “not for human consumption.” Not legal as a dietary supplement ingredient.	2026-04-29
UK (MHRA)	Not approved as a medicine. Sold as a research chemical. Supplying for human consumption is unlawful under the Psychoactive Substances Act 2016.	2026-04-29
EU (EMA)	Not approved. No licensed product.	2026-04-29
WADA (sport)	Prohibited. Listed under S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics) as a growth hormone secretagogue. In and out of competition. Detection: hair testing has documented sensitivity for MK-677 metabolites at multi-week windows; urine testing detects shorter windows.4	2026-04-29

Narrative. MK-677 is the GH-cluster compound with the clearest negative regulatory record: failed development program with a documented cardiac safety signal, FDA flagging of significant safety risks, no licensed pathway in any jurisdiction, sold exclusively through SARMs and research-chem vendors. For users in the US, the legal posture is “not banned, not approved, sold under research-only labels.” For UK users, the Psychoactive Substances Act 2016 makes supplying it for human use unlawful — the legal status is more constrained than for the injectable GH peptides.

For athletes: MK-677 is on the WADA prohibited list. Hair testing has detection windows extending several weeks beyond the last dose; out-of-competition testing can detect it.

What to track in Peptrax

The injectable GH peptides have diffuse side effects — fluid retention, joint stiffness, sleep changes — that users notice subjectively. MK-677’s documented safety signals are different: glucose dysregulation and the cardiac signal from the discontinued Adunsky trial. Both move biomarkers before they move felt experience. Tracking glucose and cardiovascular markers periodically isn’t optional precaution for MK-677 the way it would be for ipamorelin; it’s how the user catches the things the trial data flagged.

For most users, the highest-signal log is fasting glucose every 4–8 weeks (home glucose meters work fine for this), morning resting heart rate and blood pressure weekly, and subjective markers (sleep quality, dream vividness, hunger spike, ankle swelling) daily. The combination identifies the dose-related effects (insulin resistance, fluid retention) before they become symptomatic.

For sensitive-systems users, the priority log shifts to the first 4 weeks: any persistent oedema, exertional shortness of breath, palpitations, or atypical chest sensations are stop-and-reassess signals because of the Adunsky CHF signal. A written stop criterion before starting is essential for any user with cardiovascular risk factors. Glucose monitoring is non-optional for users with prediabetes or T2D.

Across all users, logging cycle position matters because MK-677’s metabolic effects accumulate with continuous dosing. The app should help users see “you’ve been on for X weeks; the published data on continuous dosing is at 12–24 months in healthy older adults; if you’re approaching that window, the cycling pattern is precautionary.” Bedtime dosing alignment with sleep tracking — vivid dreams, sleep depth, morning subjective recovery — gives the cleanest read on whether the compound is producing the sleep-architecture effect users are looking for.

For personal tracking and informational purposes only — not medical advice.