Peptides for muscle growth
Also called: muscle building peptides, best peptides for muscle growth
Clinical reviewer: Jacob Moore, MD · Last checked September 16, 2026
Which peptides are used for muscle growth?
Peptides for muscle growth refers to growth-hormone secretagogues, IGF-1 LR3, follistatin and MGF, marketed online to increase lean mass. Only one member of this group, mecasermin (Increlex), is FDA-approved, and only for a narrow pediatric growth condition; the rest are unapproved or nominated compounding substances reviewed by FDA in different categories.
What is marketed for muscle growth, and what does the evidence say?
Products sold online for muscle growth in this group include growth-hormone secretagogues, IGF-1 LR3, follistatin-344 and mechano growth factor (MGF); a 2026 review lists follistatin-344 among unapproved peptides marketed direct to patients [4]. A 2018 review says secretagogues "might ... improve lean mass in wasting states," but adds there are "few long-term, rigorously controlled studies" and calls for long-term safety research, including cancer risk [1]. A 2026 review of unapproved peptides marketed direct to patients found favorable animal results but says "rigorous human safety data are scarce" for a "gray market" operating "largely outside of regulatory oversight" [4].
Are these peptides FDA-approved, and what about IGF-1?
No product in this group is FDA-approved for muscle growth. The only approved IGF-1 product, Increlex (mecasermin), is indicated for growth failure in children age 2 and up with severe primary IGF-1 deficiency, and its label carries warnings for severe hypoglycemia with seizures, intracranial hypertension, and postmarketing reports of malignant neoplasms [2]. FDA's May 2026 list places mechano growth factor and GHRP-2/GHRP-6 in Category 3 and ibutamoren in Category 2 [3].
Related terms
Sources
- Sigalos JT, Pastuszak AW. The Safety and Efficacy of Growth Hormone Secretagogues. Sex Med Rev, 2018.
- DailyMed — Increlex (mecasermin) label
- FDA — Bulk Drug Substances Nominated for Use in Compounding Under Section 503A, updated May 14, 2026
- Mendias CL, Awan TM. Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance. Sports Medicine, 2026.
This entry is for education and is not medical advice. Talk with a licensed clinician about your own situation before starting, stopping, or changing any treatment.
