Follistatin-344
Blocks myostatin, the brake on muscle size. Real biology, but the vials sold to lifters have no human trials and uneven quality.
What it is
Follistatin-344 is bought by lifters who have stalled and want to lift the body's own cap on muscle size. The idea is sound; the product usually is not. A 1 mg vial costs real money, lasts ten days, and nobody has shown it works when injected.
The buyer is an experienced lifter, often on or past TRT, who has read about Belgian Blue cattle and myostatin-null mice and wants that lever. Follistatin is the protein that naturally soaks up myostatin, the signal that tells muscle to stop growing; more follistatin, on paper, means less brake. It is not for a beginner, not for someone with a normal training response, and not for anyone with a cancer history, because the same TGF-beta family it binds also regulates cell growth elsewhere.
User reports cluster around a fuller, more pumped look within two to three weeks of a daily course and claims of a few pounds of lean mass over a month, from people who paid for it and wanted it to work. Nothing in a controlled human setting backs them, and the dramatic animal results came from gene therapy that keeps follistatin high for months, not from a 100 mcg shot cleared the same day. If you run it, measure: weight, a tape on the arm, a photo in the same light, before and after.
The shared protocol is 100 mcg subQ once a day for 10 to 30 days, sometimes dropping to two or three shots a week after the first stretch, then a few weeks off, often three to four, before another run. That break is caution rather than a reset: there is no human data on longer runs, and it acts on muscle-growth signals throughout the body. Most people inject near the muscle they care about, though nothing shows it stays local. A 1 mg vial is ten daily doses, so a 30-day course is three vials, which makes this one of the more expensive experiments per month on the site. The named mistake is buying it without a certificate of analysis: follistatin is a 344-amino-acid protein that is hard to make, and vials have tested anywhere from full strength to nothing.
We grade it animal 3, human 1. The animal side is strong but for a different product: viral gene therapy (AAV1-FS344) that made mice and monkeys grow serious muscle, and a small muscular dystrophy trial of the same gene therapy in people. The injectable peptide has zero human performance trials. The biology is real, the delivery you can buy is unproven, and that gap is the whole story.
If you are a natural lifter with room to grow, a proper surplus and a progression plan beat this by a mile. If you want a growth-factor experiment with more data and clearer dosing, IGF-1 LR3 is the better-trodden path, and PEG-MGF is the gentler one for repair. Follistatin-344 is for the person who has done those, accepts a coin flip on vial quality, and is running it as a short, measured trial rather than a plan.
What people use it for
Muscle growth
Some evidenceBlocking myostatin produces dramatic muscle growth in animals, and follistatin gene therapy did the same in mice and monkeys. The injectable peptide has no human performance trial at all. Translate that as: the pathway is proven, the product is not.
Muscle disease
Early daysA small trial of follistatin gene therapy (AAV1-FS344) in people with muscular dystrophy showed improved walking distance. That is a one-time viral delivery that keeps the protein high for months, nothing like a daily shot. It is the only human data in this story.
Growth signals elsewhere in the body
Early daysFollistatin binds not just myostatin but activin and other TGF-beta family signals that regulate cell growth across tissues. In people taking it at these doses that risk has never been measured. It is why the cancer-history line in the safety list is not boilerplate.
How people use it
Safety, in brief
Things people sometimes notice
- Redness or a small lump at the injection site
- A very mixed response; feeling nothing at all usually means the vial was weak
- A pumped, watery fullness in the worked muscle in the first weeks
The full picture — stop signs and who should talk to a doctor first — is on the dosing guide.
Sources
The labels and studies behind this page. Each link opens the original on PubMed, DailyMed or ClinicalTrials.gov.