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Ranked by human evidence

Best Peptides for Muscle Growth, Ranked by Human Evidence

Tesamorelin has the strongest human evidence of the peptides sold for muscle growth, but its 26 randomised trials measured belly fat in people with HIV, not muscle in healthy adults. The popular options have far less: small hormone studies for CJC-1295 and ipamorelin, child growth trials for sermorelin, and MK-677 trials that measured fat-free mass but not strength.

Growth-hormone peptides like CJC-1295 and Ipamorelin are used to chase muscle and body-composition gains by raising GH and IGF-1. Human evidence for real muscle or strength gains is limited, they are research-use-only and not approved for human use, and most are banned in tested competition.

Related: Best peptides for men · Ipamorelin vs sermorelin · Tesamorelin vs MK-677 · Peptide stacking

Peptides for muscle growth, ranked by human evidence

The order is the strength of human evidence, strongest first: strong, moderate, limited, animal or lab only, then none. Ties keep the site's usual compound order. A higher rank means more and better human studies, not that a compound works for muscle growth, so check what each study measured.

Peptides for muscle growth compared: evidence level, US legal status and what human studies measured
RankCompoundEvidenceUS statusMeasured in humansGuide
1TesamorelinStrong human evidenceFDA-approved · prescription onlyVisceral belly fat in people with HIV (26 randomised trials); never tested in healthy adults for body composition.Read
2SermorelinLimited human dataUnapproved drugGrowth in children with growth hormone deficiency; an IGF-1 blood marker in hypogonadal men.Read
3CJC-1295Limited human dataResearch use onlyGrowth hormone and IGF-I levels in healthy adults (DAC form only); no muscle, strength or fat outcomes.Read
4IpamorelinLimited human dataResearch use onlyHow the body clears it in healthy men, and a Phase 2 programme in postoperative ileus that stopped for insufficient efficacy.Read
5GHRP-2Limited human dataResearch use onlyGrowth hormone, appetite and other hormones in small studies; none I verified measured muscle in healthy adults.Read
6GHRP-6Limited human dataResearch use onlyGrowth hormone release in small older studies; none showed muscle gain or better recovery.Read
7HexarelinLimited human dataResearch use onlyGrowth hormone release in short pharmacology studies; I found no controlled trial for muscle, fat or recovery.Read
8MK-677 (Ibutamoren)Limited human dataResearch use onlyFat-free mass in 3 trials of older adults and obese men; strength and performance were not measured. Not a peptide.Read
9HGH 191AALimited human dataResearch use onlySomatropin's approval trials, in growth hormone deficiency and related conditions; never in healthy adults for muscle, recovery or aging.Read
10PEG-MGFAnimal / lab onlyResearch use onlyCell and animal studies only; no controlled human trials.Read
11MGFAnimal / lab onlyResearch use onlyCell and animal studies only; no controlled human trials.Read
12IGF-1 LR3Animal / lab onlyResearch use onlyCell and animal studies only; no controlled human trials.Read
13FollistatinAnimal / lab onlyResearch use onlyCell and animal studies only; no controlled human trials.Read
14IGF-1 DESAnimal / lab onlyResearch use onlyCell and animal studies only; no controlled human trials.Read
15SLU-PP-332Animal / lab onlyUnapproved drugNone: I located no trial, case report or human dosing study.Read
  1. Prescription / GLP-1FDA-approved · prescription only

    1. Tesamorelin

    Strong human evidence

    Measured in humans: Visceral belly fat in people with HIV (26 randomised trials); never tested in healthy adults for body composition.

    Why this rating

    Twenty-six randomised controlled trials, including a randomised trial in JAMA measuring visceral and liver fat, plus safety and metabolic studies and more recent evaluation in people taking integrase inhibitors. The rating describes the volume and design of the evidence for the approved indication; no trial has tested healthy adults for body composition.

  2. Prescription / GLP-1Unapproved drug

    2. Sermorelin

    Limited human data

    Measured in humans: Growth in children with growth hormone deficiency; an IGF-1 blood marker in hypogonadal men.

    Why this rating

    Randomised trials exist but sit in paediatric growth hormone deficiency, and the review reporting the treatment regimen hedges it as limited data with the effect on final adult height yet to be determined. The nearest adult evidence is an IGF-1 biomarker result in hypogonadal men. No randomised trial in healthy adults for the marketed outcomes was located.

  3. Research peptidesResearch use only

    3. CJC-1295

    Limited human data

    Measured in humans: Growth hormone and IGF-I levels in healthy adults (DAC form only); no muscle, strength or fat outcomes.

    Why this rating

    Human pharmacokinetic data exists for the DAC form only, from two randomised, placebo-controlled, double-blind ascending-dose trials in healthy adults aged 21 to 61, reported in one 2006 paper. Those are surrogate hormone measures, not clinical outcomes, and development was discontinued at Phase 2. The without-DAC form (mod GRF 1-29) has no published human pharmacokinetic study I could locate. One entry, two very different evidence bases.

  4. Research peptidesResearch use only

    4. Ipamorelin

    Limited human data

    Measured in humans: How the body clears it in healthy men, and a Phase 2 programme in postoperative ileus that stopped for insufficient efficacy.

    Why this rating

    The selectivity finding it is famous for is in vitro and animal data only - rat pituitary cells, anaesthetised rats, conscious swine. Human data is limited to a pharmacokinetic study in healthy men (terminal half-life 2 hours) and a Phase 2 program in postoperative ileus that was discontinued for insufficient efficacy. So there is human data - and what it showed was a failure to demonstrate benefit.

  5. Research peptidesResearch use only

    5. GHRP-2

    Limited human data

    Measured in humans: Growth hormone, appetite and other hormones in small studies; none I verified measured muscle in healthy adults.

    Why this rating

    The human literature goes back to the 1990s and is mostly single-dose diagnostic testing: a 100 mcg intravenous dose separated healthy adults from patients with growth hormone deficiency, and a 2 mcg/kg dose worked as a test in children. The other studies I verified are small - increased food intake in healthy adults, 8 months of daily injections in 6 children with growth hormone deficiency, and a 5-day infusion with TRH in 14 critically ill patients. None of them measured muscle, strength or body composition in healthy adults. FDA lists GHRP-2 in Category 2 of its interim compounding policy, and WADA names GHRP-2 (pralmorelin) explicitly as a prohibited GH-releasing peptide.

  6. Research peptidesResearch use only

    6. GHRP-6

    Limited human data

    Measured in humans: Growth hormone release in small older studies; none showed muscle gain or better recovery.

    Why this rating

    GHRP-6 is one of the oldest compounds in the growth hormone secretagogue class, with human pharmacology described in small studies going back to the 1980s. None of those papers is yet in my source registry, so I describe the evidence in general terms rather than citing specific findings or figures. What exists shows it can raise growth hormone in humans; it does not establish a demonstrated benefit for muscle building, recovery or any other consumer use, and no adequately powered clinical-outcome trial supports marketed claims.

  7. Research peptidesResearch use only

    7. Hexarelin

    Limited human data

    Measured in humans: Growth hormone release in short pharmacology studies; I found no controlled trial for muscle, fat or recovery.

    Why this rating

    Human data on hexarelin is old, small and mostly confined to short GH-stimulation pharmacology studies from the 1990s and 2000s rather than trials of any consumer use. No controlled human trial of hexarelin for muscle gain, body composition or recovery exists in the registry this site cites from. I am not aware of a hexarelin study registered with a verifiable clinical-trial registry id, so none is cited here.

  8. Research peptidesResearch use only

    8. MK-677 (Ibutamoren)

    Limited human data

    Measured in humans: Fat-free mass in 3 trials of older adults and obese men; strength and performance were not measured. Not a peptide.

    Why this rating

    Three published trials gave 25 mg a day by mouth to healthy older adults or obese men and found it raised growth hormone and IGF-1 and increased fat-free mass. None measured muscle strength or athletic performance, or tested the younger people most vendors target. FDA also references a randomized, placebo-controlled trial in patients recovering from hip fracture that was stopped early over a possible link to congestive heart failure, and the published trials saw fasting glucose rise.

  9. Research peptidesResearch use only

    9. HGH 191AA

    Limited human data

    Measured in humans: Somatropin's approval trials, in growth hormone deficiency and related conditions; never in healthy adults for muscle, recovery or aging.

    Why this rating

    The parent molecule, somatropin, has strong trial evidence for its FDA-approved indications - growth hormone deficiency, Turner and Prader-Willi syndromes, and related conditions - reflected in approved drug labels (see externalRefs). None of that trial evidence was collected in healthy adults using it for the muscle, recovery or anti-aging claims this research-sold product is marketed for, and no clinical trial of a research-channel "HGH 191AA" vial itself exists. That gap - real drug, unstudied off-label consumer use, unverified vial - keeps this record at "limited" rather than higher.

  10. Research peptidesResearch use only

    10. PEG-MGF

    Animal / lab only

    Measured in humans: Cell and animal studies only; no controlled human trials.

    Why this rating

    Human evidence is essentially absent. FDA states it has identified no human exposure data on PEG-MGF administered by any route. The literature on native mechano growth factor is rodent and cell-culture work - for example, MGF messenger RNA rising quickly after muscle damage in rats (Hill 2003), and a synthetic MGF E peptide improving transplanted muscle-cell engraftment in mice (Mills 2007) - not a study of the synthetic, PEGylated consumer product. The one human study usually cited (Hameed 2003) measured MGF messenger RNA switched on by exercise in people's own muscle; nobody was injected. Researchers at two pharmaceutical companies could not reproduce the claimed effects of the MGF peptide on muscle cells (Fornaro 2014). No completed human trial has tested injected PEG-MGF for any outcome.

  11. Research peptidesResearch use only

    11. MGF

    Animal / lab only

    Measured in humans: Cell and animal studies only; no controlled human trials.

    Why this rating

    The evidence base is animal and cell-culture research into a natural splice variant of IGF-1, not a human trial of the synthetic peptide sold as MGF. The cell findings conflict: early work reported that the MGF E peptide boosted muscle precursor cell growth (Yang 2002; Kandalla 2011), but an independent two-company attempt found no effect on myoblasts or muscle stem cells (Fornaro 2014). Animal work includes heart-attack models in sheep (Carpenter 2008). No completed human trial has tested injected MGF for muscle growth, recovery or any outcome. That places it at "preclinical" - the same tier as PEG-MGF, its longer-acting relative.

  12. Research peptidesResearch use only

    12. IGF-1 LR3

    Animal / lab only

    Measured in humans: Cell and animal studies only; no controlled human trials.

    Why this rating

    I could not locate a controlled human trial of IGF-1 LR3, for muscle gain, body composition or any other consumer use, in the source registry this site cites from. What is published is cell-culture and receptor-binding pharmacology using IGF-1 LR3 as a research reagent, plus animal studies: growth and nitrogen balance in steroid-treated, diabetic and normal growing rats, blood-glucose lowering in pigs, a 7-month intranasal study in a mouse Alzheimer's model, and a one-week infusion into growth-restricted fetal sheep that did not improve growth. None is a test of the molecule as something a person injects.

  13. Research peptidesResearch use only

    13. Follistatin

    Animal / lab only

    Measured in humans: Cell and animal studies only; no controlled human trials.

    Why this rating

    No human trial has tested the injected recombinant protein sold as a research chemical. The only human trials of therapeutically raised follistatin used a one-time viral-vector gene therapy - the vector makes muscle cells produce the FST344-encoding transgene themselves - tested in small numbers of adults with Becker muscular dystrophy and sporadic inclusion body myositis. That is a different product, a different route of administration and a single-dose intramuscular injection into diseased muscle, not a repeated systemic protein injection in a healthy person. It does not transfer as human evidence for the vial sold online, which is why this stays at preclinical rather than limited.

  14. Research peptidesResearch use only

    14. IGF-1 DES

    Animal / lab only

    Measured in humans: Cell and animal studies only; no controlled human trials.

    Why this rating

    I could not locate a controlled human trial of IGF-1 DES, for muscle gain or any other consumer use, in the source registry this site cites from. What is published is in-vitro receptor and binding-protein pharmacology, and in-vivo animal studies using continuous infusion (osmotic minipump) in rats with reduced renal mass or after surgical gut resection, and bolus injection studies in pigs and marmoset monkeys measuring blood glucose - not the intramuscular injection method sold to consumers, and not a test of the molecule as a person would actually use it.

  15. Research peptidesUnapproved drug

    15. SLU-PP-332

    Animal / lab only

    Measured in humans: None: I located no trial, case report or human dosing study.

    Why this rating

    Every finding I verified for SLU-PP-332 is from mouse studies, published in peer-reviewed journals: repeated ERR agonist dosing produced exercise-mimicking muscle-fibre and metabolic changes, and enhanced treadmill endurance, in mice. I located no published human trial, case report or clinical dosing study of any kind. Vendor pages selling it as a research chemical describe human clinical activity as "emerging but early," not established, which is consistent with what I found.

Common questions about peptides for muscle growth

What is the best peptide for muscle growth?

By strength of human evidence, tesamorelin ranks first, but its trials measured visceral fat in people with HIV-associated lipodystrophy, not muscle in healthy adults. I found no peptide here with a trial showing it builds muscle or strength in healthy people who train. MK-677, which is not a peptide, increased fat-free mass in trials of older adults and obese men; strength was not measured.

Does CJC-1295 really work?

It raises growth hormone. In 2 placebo-controlled trials in healthy adults, the long-acting form with DAC raised growth hormone and IGF-I for days after one injection. Those trials measured hormone levels, not muscle, strength or fat, and development stopped at Phase 2. The form without DAC has no published human pharmacokinetic study I could locate.

Which is better, sermorelin or ipamorelin?

Neither has a trial in healthy adults for muscle or body composition, so the evidence picks no winner. Sermorelin acts on the GHRH receptor; its controlled trials were in children with growth hormone deficiency, and its US approvals were withdrawn after the sponsor discontinued it. Ipamorelin acts on the ghrelin receptor; its human data is a pharmacokinetic study and a Phase 2 programme in postoperative ileus (bowel paralysis after surgery) that stopped for insufficient efficacy.

Does sermorelin build muscle?

I found no trial showing it does in adults. Its controlled trials were in children with growth hormone deficiency and measured growth. The nearest adult result is a rise in IGF-1, a blood marker, in hypogonadal men.

What are the downsides of peptides for muscle growth?

Research-chemical vials are not FDA-approved, so no regulator reviews their identity, purity or dose. CJC-1295, ipamorelin, GHRP-2 and GHRP-6 are banned at all times in tested sport under WADA rules. FDA lists GHRP-2, GHRP-6, ipamorelin and MK-677 as compounding substances with potential significant safety risks, and the MK-677 trial FDA cites was stopped early over a possible heart-failure signal.

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