Any new or unusual symptom after dosing. Because this compound has little or no human safety data, there is no established list of 'expected' effects to reassure you against — treat anything abnormal as a signal.
Stop at the first clearly abnormal reaction and reassess. Keep the vial and lot number in case you need to describe what you actually took.
Any severe or fast-worsening symptom — difficulty breathing, chest pain, fainting, severe pain — is a 911 call regardless of the compound.
Allergic reaction: hives, swelling of the lips, tongue or throat, wheezing or dizziness can escalate to anaphylaxis within minutes — call 911 immediately. Site infection: spreading redness, heat, swelling, pus or fever is not wait-and-see; an abscess or cellulitis can need drainage or IV antibiotics. Unverified product: grey-market vials are frequently mislabelled or contaminated, so a reaction may be to endotoxin or the wrong contents, not the named compound.
Follistatin binds and neutralises myostatin, the TGF-beta family member that acts as a brake on muscle growth. Remove the brake and muscle mass increases — a mechanism dramatically confirmed by myostatin-null cattle, dogs and the well-documented human case of myostatin deficiency. FS-344 is the precursor isoform that is processed to FS-315. It also binds activin A, which is where the trouble starts.
Essentially all of it is preclinical or gene-therapy work in animals. Human data for administered follistatin protein are absent. Meanwhile the broader myostatin-inhibition field has a sobering track record: multiple pharmaceutical myostatin inhibitors have failed in trials, producing measurable muscle mass increases without corresponding functional benefit. Bigger muscle did not mean better outcomes.
Not FDA-approved. Gene therapy prohibited in sport, and myostatin inhibition prohibited (WADA S4.4).
No human safety data. The activin-binding activity is the serious unknown: activin signalling is involved in reproductive function, inflammation and tumour suppression, so systemic follistatin is not a clean myostatin switch. A protein of this size administered exogenously also raises real immunogenicity concerns.
No human trial has ever established a dose for this compound. Any figure circulating online is extrapolated from animal studies or copied between vendors — it was not validated in people. That absence is the single most important dosing fact on this page. Evidence is animal and gene-therapy work only.
Reported from clinical trials or FDA labelling as a matter of record. It is not a recommendation, and for unapproved compounds no dose has been shown safe or effective in humans.
Above is what was administered in trials or on FDA labels, reported as fact. We do not convert it into a personal protocol, calculate a dose for your body weight, or tell you what to inject or how to reconstitute it — that decision belongs with a licensed physician. See our editorial policy.
Regulatory status changes. This page reflects our reading of public sources as of July 2026 and should be independently verified before it is relied upon.