Follistatin 344 is sold as a lyophilised powder in 1 mg vials and dosed in micrograms on vendor pages, but no study has ever injected follistatin protein into a person. The human record consists of gene-therapy trials, one anti-doping analysis of what black-market vials contain, and one case series of eye injuries. This page sets out each, then the arithmetic for the vial sizes, so that the vendor figures can be read for what they are.
The compound itself — myostatin, activin and the animal work — is covered in Medibact's Follistatin 344 guide. The follistatin 344 calculator works any vial and volume.
A protein, not a short peptide
UniProt's entry for human follistatin (P19883) is titled "Follistatin 344": the gene encodes 344 amino acids, of which residues 1–29 are a signal sequence the cell cuts off. The circulating protein is the remaining 315 residues (FS315), carrying two sugar chains and 36 cysteines; a splice variant, FS288, is shorter. By molecular weight the mature chain is about 34,750 g/mol before glycosylation, against 1,419.5 for BPC-157 and 4,114 for semaglutide.
Two things follow for anyone reading a vial label. First, micrograms of follistatin are far fewer molecules than the same micrograms of a small peptide — 100 mcg is about 2.9 nanomoles, against about 70 for BPC-157. Second, a glycosylated 315-residue protein is a product of recombinant expression, and the anti-doping study below found the tag that recombinant production leaves on every follistatin-containing product it tested.
The human trials are gene therapy
| Record | What was given | Dose unit | Status on 2026-09-26 |
|---|---|---|---|
| NCT01519349, phase 1 (Mendell and colleagues) | AAV1.CMV.FS344 into both quadriceps, Becker muscular dystrophy and inclusion body myositis | 3 or 6 × 10¹¹ vector genomes/kg per leg | completed; published 2015 and 2017 |
| NCT02354781, phase 1/2 | rAAV1.CMV.huFollistatin344, Duchenne muscular dystrophy | vector genomes | completed, 3 enrolled, results posted |
| NCT06411366, phase 1 (Minicircle) | follistatin-344 plasmid | plasmid | completed 2023-08; no results posted |
| NCT07285629, early phase 1 (Minicircle) | follistatin and klotho plasmid | plasmid | completed 2026-04; no results posted |
| NCT07443826, phase 1/2 | AAV-follistatin with an angiogenesis gene | vector genomes | recruiting |
In the Becker trial (PMID 25322757), two of three men on the lower dose walked 58 m and 125 m further in six minutes and one did not change; on the higher dose two improved by 108 m and 29 m and one did not. In the inclusion body myositis trial (PMID 28279643), treated subjects' walking distance rose 56 m a year against a 25.8 m decline in eight untreated comparison subjects. Neither dose converts to micrograms of protein: a vector dose sets how many cells receive the gene, not how much follistatin they then make.
What black-market vials contained
Reichel, Gmeiner and Thevis (Drug Test Anal 2019, erratum 2020), working in WADA-accredited laboratories, bought 17 products labelled follistatin 344 (a few labelled 315). Nine contained follistatin; several of the rest contained other growth-promoting peptides, MGF and GHRP-2 among them. All nine carried a His-tag and a large share of oligomers — protein chains stuck together. The His-tag is how their urine test distinguishes injected follistatin from the body's own, down to about 0.1 ng/mL.
The one human harm report
Dağ and colleagues (Int Ophthalmol 2020) describe 11 men, mean age 36.8, who came to one eye clinic with blurred vision and fluid under the retina (central serous chorioretinopathy) after injecting follistatin 344 under the abdominal skin. Every one had injected a whole 1 mg vial at a time. Eight had injected once, and their fluid cleared in about 2.3 months; three had injected repeatedly, and all three had recurrences. A case series cannot give a rate or prove cause. It is the only published human outcome of injected follistatin 344 found on 2026-09-26.
The vendor figures
This site's peptide dosage chart, from vendor pages read on 2026-09-18, records 100 to 200 mcg under the skin daily, up to 300 mcg, in blocks of 2 to 4 weeks. No trial, label or published study stands behind those numbers. Against them, the case-series injections of 1 mg (1,000 mcg) are five to ten times the lower daily figures, in one injection.
Units per vial
Units on a U-100 syringe = mcg ÷ mcg/mL × 100. Vial sizes in this site's data are 1, 2 and 5 mg:
| Amount | 1 mg + 1 mL (1,000 mcg/mL) | 1 mg + 2 mL (500 mcg/mL) | 2 mg + 2 mL (1,000 mcg/mL) | 5 mg + 2.5 mL (2,000 mcg/mL) |
|---|---|---|---|---|
| 100 mcg | 10 | 20 | 10 | 5 |
| 200 mcg | 20 | 40 | 20 | 10 |
| 300 mcg | 30 | 60 | 30 | 15 |
| 1,000 mcg (1 mg) | 100 | 200 | 100 | 50 |
A 1 mg vial holds between three and ten portions at the vendor figures. The mg to mcg page covers the conversion behind these rows, and the insulin syringe units page the scale.
What is not established
No dose of injected follistatin protein has been tested in people, no pharmacokinetic figure exists for it, and whether a subcutaneous injection of a recombinant 35-kilodalton glycoprotein reaches muscle is not established by any published human study. The anti-doping analysis found that roughly half the products tested did not contain follistatin. The vendor figures are reported, not endorsed, and the molar comparison and unit figures are arithmetic. Nothing on this page is a dose or a schedule.
Sources and dates
Opened 2026-09-26: UniProt P19883 (sequence, signal peptide, isoforms, glycosylation sites); DailyMed search for follistatin; ClinicalTrials.gov v2 intervention search for follistatin (15 records) and the records for NCT06411366 and NCT07285629; PubMed abstracts for Mendell et al., Mol Ther 2015 (PMID 25322757) and 2017 (PMID 28279643), Reichel, Gmeiner and Thevis, Drug Test Anal 2019 (PMID 31758732; erratum PMID 33460286) and Dağ et al., Int Ophthalmol 2020 (PMID 32671599); vendor figures as recorded on this site's dosage chart (vendor pages read 2026-09-18). Molecular weight from the UniProt sequence and all unit figures are arithmetic by this site. Corrections go to the contact page.