FLGR-242

FLGR-242 is sold as a modified piece of follistatin joined to an albumin-binding tail, labelled for research use only. It has no published research in any index we searched (re-checked 16 October 2026).

It goes under the skin, in the belly only — never into muscle.

The seller's main claims — that it blocks myostatin without binding activin, lasts for weeks, reaches muscle directly and preserves lean mass — have no published data on this product, and what is in the vial has not been independently identified. A protocol that circulates has it taken once a week, in the morning, fasted.

Best for

Nothing that can be stated from evidence. There is no published study of FLGR-242 in any species, no toxicology, no pharmacokinetics and no registered trial, so no population has been shown to benefit. It is listed so that people who already have it can look it up and track what they take.

What to expect

Unknown. No pharmacokinetic study of FLGR-242 exists in any species, so there is no measured time to peak, duration or half-life. The 19-day figure that circulates is a patent's assertion, reasoned from albumin's own half-life in people, not a measurement.

Pairs with

Nothing, on any evidence basis. With no characterised mechanism there is nothing to predict an interaction from, and no way to tell which of two products caused an effect or a side effect.

Research protocol

No dose of FLGR-242 has ever been published in a study, in any species, by any route — so nothing below is a recommendation.

FLGR-242 goes under the skin (subcutaneous) only, never into muscle: into muscle it can be painful.

One protocol in circulation runs 2.5 mg once a week for four weeks, then 5 mg weekly for eight, then 10 mg weekly for twelve, with women said to start lower, at 1–1.25 mg a week, each dose taken in the morning, fasted (on an empty stomach). It carries no source, and no study of this compound exists to have produced one.

The seller's own usage guide prints a different schedule. With the follistatin part undisclosed, a milligram figure describes a mass of powder rather than a known quantity of a defined substance.

If the roughly 19-day half-life claimed for it were right, weekly dosing would build up to about 4.4 times the stated dose at steady state; no half-life has been measured. The certificates on file are for 5 mg vials, so the 10 mg rung is two vials per injection.

The protocol states no endpoint, no monitoring and no stopping rule.

Typical research dosing

Typical start1 mgwomen · start 1–1.25 mg/week · circulating figure, no published source2.5 mgweeks 1–4 · circulating figure, no published source5 mgweeks 5–12 · circulating figure, no published source10 mgweeks 13–24 · circulating figure, no published source

How often: Weekly
When: Morning, fasted
Route: Subcutaneous only (not into muscle)
Vial & water: 5 mg vial in 1 mL = 5 mg/mL · 1 mg = 20 units on a U-100 syringe
Cycle: The circulating protocol escalates 2.5 mg/week for 4 weeks, then 5 mg/week for 8, then 10 mg/week for 12 — with no stated endpoint, no monitoring and no stopping rule. Women are said to start lower, at 1–1.25 mg/week. It has no published source, and no study of this compound exists to have produced one.

⚠ Research-compound safetyNo published research, and no confirmed identity: no study of this compound appears in any index we searched, and no document establishes what is in the vial. Under the skin (subcutaneous) only — not into muscle; into muscle it can be painful. The seller says it blocks myostatin without binding activin, lasts for weeks, binds albumin tightly, reaches muscle directly and preserves lean mass; none of it has published data on this product. Its certificates measure purity and quantity, not identity. It is sold labelled for research use only, and no regulator has approved it for any use.

The same numbers the goodtides app and the Dose Calc use — a research reference, not a prescription. Responses are individual; research protocols start at the low end.

How it works

FLGR-242 has no published research in any index we searched (re-checked 16 October 2026), so what is said about it comes from the seller. Here is each claim, with what has been published or measured on it.

The seller says it blocks myostatin without binding activin, with “no unwanted cellular growth signals”. The data: none published — no binding measurement has been made public, and the follistatin sequence is undisclosed.

The seller says it has an extended half-life — its usage guide says “active 19 days per injection” in one place and 14–15 days in another. The data: not measured — no half-life has been published for this product in any species; the 19-day figure is a patent's assertion, reasoned from albumin's own half-life.

The seller says it binds albumin tightly, at “<20 nM”. The data: measured in the patent only on a different construct, its alpha-Klotho version (7.94 nM against human albumin); none has been published for this product.

The seller says it has “superior tissue distribution” and reaches skeletal muscle directly. The data: no published data on this product — no distribution study has been published in any species.

The seller says it preserves lean mass and is “anabolic — aggressively so”. The data: no published data on this product — no study of its effect on muscle or body composition has been published in any species.

The seller says it is a modified fragment of follistatin-344, about 40 kDa in all. The data: not disclosed or independently confirmed — the follistatin part's sequence is undisclosed (only the albumin-binding tail's is published, and it matches a 2025 patent), and no certificate states a molecular weight or a sequence.

The seller says ≥99% purity, US GMP manufacture and “third-party verified” certificates. The data: the three certificates we read do report 99.71–99.79% purity and roughly the labelled amount, which measures purity and quantity, not identity; GMP manufacture is the seller's statement, and the certificates say nothing about it.

The seller lists 17 research references. The data: the 17 papers are real, and none studies FLGR-242 — 13 are on follistatin, mostly in mice, rats or cells; 3 are on FSTL1, made from a different gene; 1 is a retracted paper, cited by its retraction notice.

The seller's usage guide says redness or swelling at the injection site “is not an allergic reaction”. The data: none — a reaction to this product cannot be assumed harmless, and widespread hives, swelling of the lips or tongue, or trouble breathing need urgent care.

What we checked. The tail is real: its last 18 amino acids, RLIEDICLPRWGCLWEDD, are SA21, an albumin-binding peptide published in 2002; the first 11 are a standard glycine-serine linker; and the whole tail, GGSGGSGGSGGRLIEDICLPRWGCLWEDD, is sequence 4 of US patent 12,377,158 B1, granted in 2025, which covers the tail and does not mention activin or myostatin.

The follistatin part, which decides what the molecule is and what it binds, is undisclosed. About 40 kDa fits nearly the whole working follistatin protein (315 amino acids, about 34.8 kDa before sugars) plus the tail (about 2.95 kDa), not a small fragment.

Natural follistatin binds activin more tightly than myostatin — 1.72 nM against 12.3 nM in one published measurement — so sparing activin would take a change to the follistatin part, and the seller has not described one.

Pharmacokinetics

Half-life: Not published. No pharmacokinetic study of FLGR-242 exists in any species. The ~19-day figure in circulation (the seller's usage guide also says it stays active for 14–15 days) traces to a 2025 US patent on the albumin-binding tail, which asserts it from albumin's own 19-day half-life in people and reports no measurement. In the 2002 paper that introduced this tail peptide, an antibody fragment fused to a related albumin-binding sequence reached 25 to 43 percent of albumin's half-life: 32.4 hours in rabbits and 10.4 hours in mice. The patent's only follistatin figure, 7 days in dogs, comes with no data.
Peak: No data. No pharmacokinetic measurement of this compound has been published in any species.
Absorption: No data. No absorption, distribution or route-comparison study exists.
Bioavailability: No data. No bioavailability figure has been published for this compound by any route.

References35

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This page is educational reference material about compounds studied in research settings. It is not medical advice, and nothing here is a recommendation to buy, possess, or use any compound. Research findings described are from published literature; individual compounds may not be approved for human use. Talk to a licensed clinician about anything that affects your health.