Follistatin calculator
A protein that binds and neutralizes myostatin, studied for muscle growth. Investigated via gene therapy; peptide use is unstudied and risky.
Also known as: Follistatin 344, FST, Myostatin-binding protein
FDA status — not an approved drug Not FDA-approved for any use. Follistatin is a research protein; direct peptide use has no human trials and is not reviewed by FDA.
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What Follistatin is
Follistatin is a naturally occurring protein that binds and neutralizes myostatin, the body's built-in brake on muscle growth. It has drawn intense interest for muscle building. Human exploration has been limited to gene-therapy approaches for muscular dystrophy; injected follistatin peptide has no human trials.
Research depth: 2/5 Strong animal muscle data and small human gene-therapy studies; no trials of injected peptide. Human trials: Gene therapy only. This measures how much has been studied — counting animal and laboratory work — not whether it works for you.
How Follistatin works
Myostatin (GDF-8) signals muscle to stop growing. Follistatin binds myostatin and related proteins, preventing them from acting, which releases that brake and allows increased muscle growth. Animals lacking myostatin or overexpressing follistatin develop dramatically increased muscle mass. Follistatin also affects other signaling, including reproductive hormones.
Follistatin side effects
Commonly reported
- No human safety data for injected peptide
- Theoretical effects on reproductive hormone signaling
Serious — seek medical care
- No human trials of injected follistatin peptide
- Myostatin blockade could have unstudied effects on the heart and tendons
- Prohibited in sport by WADA (gene doping concern)
This list is not exhaustive. Report anything unexpected to the clinician who prescribed it. If you have severe abdominal pain, trouble breathing, or signs of an allergic reaction, seek care the same day. See also our guide to peptide side effects by class.
A worked example
A 1 mg vial reconstituted with 2 mL of bacteriostatic water gives 0.5 mg/mL. A 200 mcg dose is then 0.4 mL — about 40 units on a 100-unit insulin syringe, giving roughly 5 doses per vial before accounting for residual volume left in the vial and syringe.
Prefer paper? Download the printable Follistatin dosing chart (PDF) — every vial size and water volume in syringe units, with the same review byline as this page. All charts →
Commonly cited dose range
Figures circulating for Follistatin run from 100 mcg to 500 mcg. No established dosing exists for the peptide form — clinical exploration has used gene therapy, not injected peptide. Figures shown are reference points in micrograms. There is no approved or established dose.
Read this as reference information, not instruction. These numbers describe what is commonly discussed, not what is right for any individual. Dose, frequency, and whether to use Follistatin at all are decisions for a licensed clinician who knows your history.
Common questions
Has follistatin been tested in humans?
Only via gene therapy (delivering the follistatin gene, not the peptide) in small studies for muscular dystrophy. Injected follistatin peptide has no human trials.
How does follistatin build muscle?
It binds and neutralizes myostatin, a protein that limits muscle growth. With myostatin blocked, the brake on muscle growth is released. This is why animals engineered to lack myostatin are heavily muscled.