Search results for this phrase are full of rankings that cite no trials. We read the published studies and the vendor listings instead. This page sets out what each commonly named compound is, what a trial has actually measured, and who sells it as a research material. It is a reading of the literature and not advice to use anything. Research vendors label these products for laboratory use only.
Is there a best peptide for muscle growth?
No peptide has been shown to be the best, and for most of the popular names no published trial we found measured muscle at all. What exists is a few studies that measured hormone levels, a few that measured lean mass, and a lot of animal and cell work. The table separates them.
What each compound is and what has been measured
Swipe the table sideways to see every column.
| Compound | What it is | What we found published | Research vendors listing it |
|---|---|---|---|
| CJC-1295 | A growth hormone releasing hormone analog. The without DAC form is 29 amino acids. | A 2006 trial gave the long-acting form to healthy adults and measured growth hormone and IGF-I levels. It did not report muscle. | All four vendors we review |
| Ipamorelin | A five amino acid growth hormone secretagogue. | The 1998 paper that described it reports work in rat cells, rats and pigs. We found no human trial that measured muscle. | All four vendors we review |
| Sermorelin and tesamorelin | Growth hormone releasing hormone analogs. | Tesamorelin has an FDA-approved label (Egrifta) for excess abdominal fat in HIV-infected adults with lipodystrophy, and the label says it is not for weight loss management. | All four vendors we review |
| IGF-1 LR3 and PEG-MGF | Modified forms of insulin-like growth factor 1 and of a mechano growth factor. | We found no human trial of either. | Core Power Peptides lists both. Peptides for Sale lists PEG-MGF only. American Peptides lists IGF-1 LR3 only. |
| Follistatin 344 | A protein studied in muscle disease. | The human work we found is gene therapy in six people with inclusion body myositis, which is a different product from a vial of protein. | Core Power Peptides and Peptides for Sale |
| MK-677 (ibutamoren) | An oral ghrelin mimetic. It is not a peptide. | A 2008 trial in 65 older adults measured fat-free mass. Details below. | None of the four vendors we review |
The one trial that measured a muscle-related change
The closest thing to a muscle result among these names belongs to MK-677. In a 2008 trial of 65 healthy adults aged 60 to 81, fat-free mass fell by 0.5 kg on placebo and rose by 1.1 kg on MK-677 over a year. The authors saw no change in strength or function and said the study was too small to test it. Fasting blood glucose rose by about 5 mg/dL and insulin sensitivity fell. Ranking pages often list MK-677 as a peptide, and it is not one. The FDA's page on compounding risks places ibutamoren in category 2 and cites a separate trial in hip fracture patients that stopped early over a possible heart failure signal.
What the hormone studies tell you
Hormone studies tell you about the hormone. The 2006 CJC-1295 trial raised mean growth hormone concentrations 2 to 10 fold for six days or more, and IGF-I 1.5 to 3 fold, in healthy adults. It reported those levels and safety, and nothing about muscle. A 1997 trial of a growth hormone releasing hormone analog in 19 older adults did report lean body mass, and found an increase in men only. That is a small sample from almost three decades ago, and the analog was a relative of the products listed above, not one of them. Our post on CJC-1295 and ipamorelin covers that pair in more detail.
Follistatin and the myostatin pathway
The published human trial of follistatin we found delivered the gene to the thigh muscles of six people with sporadic inclusion body myositis using a viral vector, and it reported a longer six minute walk than a matched untreated group. A later commentary in the same journal carries a title calling the functional claims unfounded, so the result is contested. It says little about a lyophilized protein vial. A separate trial of bimagrumab, an antibody that blocks activin type II receptors, reported thigh muscle volume 5.0% higher at week 24 against a 1.3% fall on placebo in 67 people with COPD and low muscle mass. Walking distance did not improve.
What the vendor paperwork looks like
Peptryn's ipamorelin 10 mg page () states lot 2026-08-05 at 99.34% purity by HPLC-UV-MS with a negative endotoxin result, and its CJC-1295 without DAC 10 mg page states the same lot date at 99.11%. Both name MZ Biolabs as the tester, and the ipamorelin certificate links to a report hosted on the lab's own site. Core Power Peptides says on its ipamorelin and follistatin 344 pages that a COA is provided, and on its IGF-1 LR3 page that a COA is available on request. We found no certificate file linked from those product pages ().
Core Power Peptides also describes research applications on these pages that include skeletal muscle hypertrophy models. That is the vendor's description, and no trial we read measured it for the compound. Our guide to reading a COA shows what each line of a certificate can and cannot prove. The Core Power Peptides review and the Peptryn review list what we could not confirm for each.
Sports and FDA status
Two things are worth knowing before anyone buys. The World Anti-Doping Agency's 2026 Prohibited List, as reproduced by the Cologne anti-doping laboratory, names growth hormone releasing hormone analogs such as CJC-1295, sermorelin and tesamorelin, secretagogues such as ipamorelin and ibutamoren, IGF-1 and its analogues, and mechano growth factors. The FDA's bulk substances page, current as of 22 April 2026, lists ipamorelin acetate in category 2 for outsourcing facilities, and its entry for CJC-1295, in the list of withdrawn nominations, still records serious adverse events including increased heart rate and a systemic vasodilatory reaction.
Those are rules about compounding and competition, and they say nothing definitive about research chemicals. They do show that regulators have looked at these compounds and raised safety questions. For BPC-157 and TB-500, see what is and is not known about BPC-157 and TB-500.
Frequently asked questions
Which peptide is best for muscle growth?
No peptide has been shown to be the best. Most trials we found measured hormone levels. The one that measured fat-free mass tested MK-677, which is not a peptide, and it saw no change in strength.
Are research peptides legal to buy?
Vendors sell them labeled for laboratory research only. Our guide to research-use-only labeling explains what that label does and does not cover. This site gives no legal advice.
Would these show up on a sports drug test?
The 2026 WADA list, as reproduced by the Cologne laboratory, names growth hormone releasing hormone analogs, secretagogues, IGF-1 and mechano growth factors. Athletes who are tested should read the current list themselves.