What Is Follistatin-344? Dosage, Half-Life & How to Track It

What Follistatin-344 is and how it works

Follistatin is a protein your body already produces, and its job is to bind and inactivate myostatin — a signaling molecule whose entire biological purpose is to limit muscle growth. Animals and rare human case reports with naturally low or absent myostatin function, including a well-documented double-muscled cattle breed, show dramatically greater muscle mass, which is what first pointed researchers toward myostatin inhibition as a target.

The "344" matters more than it looks. FST-344 is the precursor form that gets processed into FST-315, the major isoform that circulates systemically through the blood — both of these are systemic forms. The isoform that binds heparan sulfate proteoglycans on cell surfaces and stays largely localized wherever it is produced is a separate splice variant, FST-288. That structural difference is why the FST-344/FST-315 form — not FST-288 — is the one researched for body-wide muscle effects rather than a purely local one.

The evidence base is almost entirely preclinical: animal studies, including gene-therapy approaches in muscular dystrophy models, show substantial muscle-mass increases from myostatin/activin blockade. Human data is limited to small, mostly gene-therapy-based clinical trials for specific muscle-wasting diseases — not the kind of general-population safety and dosing data that exists for an approved drug. Treat any human dosing information as community-derived and unvalidated, not clinical.

Typical dosing & reconstitution

Follistatin-344 ships as a lyophilized powder reconstituted with bacteriostatic water. Community-reported research protocols cluster around 100 mcg subcutaneously once daily, run for a short cycle — commonly two to four weeks — rather than continuous long-term use, partly reflecting how little is known about effects beyond that window.

At 1.0 mg/mL, a 100 mcg dose is a clean 10 units on a standard U-100 insulin syringe. Because vials are typically sold in small 1–2 mg sizes, a single vial covers only a handful of days at this dose — worth factoring into supply planning, which the calculator does automatically.

Half-life & what it means for frequency

Follistatin-344’s human plasma half-life is not well characterized in published literature; what is understood from animal pharmacokinetics is that it clears relatively quickly, on the order of hours, consistent with most non-modified circulating proteins of its size. That is the basis for once-daily dosing in the protocols that exist, though it is an extrapolation rather than a validated human figure.

The short, uncertain half-life is one more reason cycles run short: there is no long-tail depot effect to lean on, so the entire premise of a research protocol depends on daily consistency for however many weeks it is run.

What to track & common side effects

Because rigorous human safety data does not really exist outside narrow clinical-trial contexts, there is no established human side-effect profile to point to the way there is for BPC-157 or CJC-1295. Anything reported outside formal trials is anecdotal.

Given the thin evidence base, what is actually worth tracking is the honest version: dose, cycle length, and whatever muscle or strength marker you are evaluating — logged consistently enough to have any real signal, with appropriately low confidence in what a change, or lack of one, actually means.

Frequently asked questions