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Limited human dataNot FDA approved

Follistatin 344

Also known as: Follistatin · FS344 · FST-344 · FS-344 · Follistatin-344

Updated 24 sources

Follistatin is a protein your body already makes. It grabs myostatin, the signal that caps how much muscle you can carry. FS344 is the 344-amino-acid precursor that becomes FS315 in the blood. The headline muscle gains come from gene therapy in mice, monkeys and two small human trials, not from injecting the protein. Gray-market 1 mg vials run 50 to 200 mcg a day for short cycles, and one lab found real follistatin in only 9 of 17 products.
Calculate with Follistatin 344Dosage chart

Quick facts

Half-life
  • Native FS315 had PK poorly suited to an injected drug in a Lilly study; an Fc-fused version had about 100-fold longer terminal half-life. No human figure.
  • About 90 minutes for FS344, per one guide, with no source given.
  • 2 to 4 hours for recombinant protein, per another guide.
  • About 35 hours, per a third guide, with no source given.
Routes
  • Subcutaneous injection
  • Intramuscular injection
Forms
  • Vial (powder)
Reported dose ranges
  • 50 to 500 mcg (subcutaneous injection)
  • 1 to 2.5 mcg/kg (subcutaneous injection)
  • 50 mcg (intramuscular injection)
Vial sizes
  • 1 mg
FDA status
  • Not FDA approved
WADA
  • Prohibited

What people use Follistatin 344 for

  • Muscle growth past a plateau, by blocking myostatin
  • Short add-on cycles next to GH, IGF-1 LR3 or GH secretagogues
  • Body recomposition during a diet
  • Longevity interest, borrowed from gene therapy data

How it is thought to work. Myostatin limits muscle by binding activin type II receptors. Follistatin blocks that binding, and mice built to make extra follistatin in muscle gained muscle mass comparable to myostatin-knockout mice. It also binds activin, which ties it to FSH and fertility. FS344 is processed into FS315, a circulating form with 10-fold lower activin affinity than tissue-bound FS288, which is why gene therapy trials chose it. A Lilly study found native FS315's pharmacokinetics poorly suited to an injected drug.

Follistatin 344 dosing

12 protocols from studies, guides and community reports, grouped by goal. Tap a source badge to see where a number came from.

Injected12

Standard (guide)

Amount
100 to 200 mcg
How often
Once daily, post-workout preferred
Route
SubQ, vial (powder)
Cycle
20 to 30 days
Rest
3 to 4 weeks off

Conservative (guide)

Amount
100 mcg
How often
Once daily
Route
SubQ, vial (powder)
Cycle
10 to 20 days
Rest
3 to 4 weeks off

Advanced (guide)

Amount
200 to 300 mcg
How often
Once daily
Route
SubQ, vial (powder)
Cycle
10 to 20 days
Rest
4 weeks off
Timing and details

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By body weight (guide)

Amount
1 to 2.5 mcg/kg
How often
Once daily
Route
SubQ, vial (powder)
Timing and details

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Beginner (guide)

Amount
50 mcg
How often
Once daily
Route
SubQ, vial (powder)
Cycle
4 weeks, then assess strength and size

Standard with training (guide)

Amount
75 to 100 mcg
How often
Once daily
Route
SubQ, vial (powder)
Cycle
6 weeks
Rest
4-week washout
Timing and details

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Every other day (guide)

Amount
100 mcg
How often
Every other day, in the morning
Route
SubQ, vial (powder)
Timing and details

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One vial, short cycle

Amount
100 mcg
How often
Once daily
Route
SubQ, vial (powder)
Cycle
10 to 20 days, one 1 mg vial
Rest
Several months off
Timing and details

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First-timer

Amount
50 to 100 mcg
How often
Once daily
Route
SubQ, vial (powder)
Cycle
10 to 14 days, a single short cycle
Timing and details

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Extended

Amount
100 to 200 mcg
How often
Once daily
Route
SubQ, vial (powder)
Cycle
Up to 30 days
Timing and details

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Twice a week

Amount
500 mcg
How often
Twice weekly
Route
SubQ, vial (powder)
Cycle
4 to 5 weeks, one 1 mg vial
Timing and details

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Pre-workout into the muscle

Amount
50 mcg
How often
Training days only
Route
IM, vial (powder)
Cycle
8 weeks on
Rest
8 weeks off
Timing and details

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Doses shown are what sources report, labelled by origin. Not medical advice.

Full Follistatin 344 dosage guideEvery titration step in syringe units, missed doses and how to mix.

Vial strengths and syringe units

Every Follistatin 344 vial size with the water volumes sources use. Units are what to draw on a U-100 insulin syringe, worked out exactly.
Follistatin 344: concentration and U-100 syringe units for each vial size and water volume
WaterStrength50 mcgdose, units100 mcgdose, units200 mcgdose, units
1 mg vial
0.5 mLCompetitor guide2 mg/mL2.50.025 mL50.05 mL100.1 mL
1 mLCompetitor guide1 mg/mL50.05 mL100.1 mL200.2 mL
2 mLCompetitor guide0.5 mg/mL100.1 mL200.2 mL400.4 mL
3 mLCompetitor guide0.333 mg/mL150.15 mL300.3 mL600.6 mL
Units are on a U-100 insulin syringe (100 units = 1 mL). U-50 and U-30 barrels read the same units.Water volumes from

Doses shown are what sources report, labelled by origin. Not medical advice.

Calculate with this peptideYour vial, your water, your dose: Follistatin 344 in syringe units, with the math shown.

Follistatin 344 side effects

What trials and labels report, kept apart from what users and guides report. Frequencies are worded as each source states them.

Reported in studies and labels2

From clinical trials and regulatory documents.

  • Fluid under the retina (central serous chorioretinopathy)

    11 male bodybuilders at one eye clinic, all after injecting whole 1 mg vials. It cleared in about 2.3 months after one injection and came back in 3 who injected again

  • Lower FSH and fertility effects

    Theoretical. Follistatin can suppress FSH through activin, which is why trials chose FS344. The Becker gene therapy trial reported no adverse effects

Reported by users and guides5

From community reports and dosing guides. Not measured rates.

  • Injection-site redness, swelling or itching

    The most common effect in guides. Community members note unusually painful injections

    How people manage it

    • Rotate injection sites.

  • Fatigue

    Mild, in the first 2 to 3 days or occasionally during a cycle, per guides

  • Joint stiffness or discomfort

    Occasional to rare, per guides, which link it to muscle outpacing tendons

    How people manage it

    • Guides pair it with BPC-157 and TB-500 for connective tissue.

  • Bigger appetite

    Noted by several community members and one guide

  • Water retention and blood-pressure changes

    Anecdotal, mild and transient, per one guide

All 7 Follistatin 344 side effects and how people manage themEvery management tip, who should not use it, and side-effect questions.

Who should avoid it

  • Pregnancy, or trying to conceiveCondition

    FSH suppression could affect fertility, per guides; never studied in pregnancy.

  • Active cancerCondition

    Activin has both tumour-suppressing and tumour-promoting roles; guides list it as a theoretical concern.

  • Drug-tested sportCondition

    Banned at all times, and black-market FS344 is detectable in urine and serum.

Storage

Powder (before mixing)

Temperature
-80 to -20 °C

Freezer at -20 °C or colder for long-term storage, years at -20 to -80 °C per one guide.

Powder (before mixing)

Temperature
2 to 8 °C

Fridge at 2 to 8 °C for short-term storage, months per one guide.

Powder (before mixing)

Room temperature or fridge, protected from light, per one guide.

Mixed vial

Temperature
2 to 8 °C
Use within
7 to 14 days

Fridge at 2 to 8 °C for 7 to 14 days; the guide suggests finishing within 7 days and freezing extra aliquots at -20 °C for up to 30 days.

Mixed vial

Temperature
2 to 8 °C
Use within
14 to 21 days

Fridge at 2 to 8 °C, use within 14 to 21 days. This guide says freezing the mixed solution damages the protein.

Mixed vial

Temperature
2 to 8 °C
Use within
30 days

Fridge at 2 to 8 °C, use within 30 days. Never freeze.

Mixed with: Bacteriostatic water

Mixing. It is a whole protein, so swirl gently and never shake; it can take 2 to 5 minutes to dissolve. Discard it if cloudy. At 1 mL in a 1 mg vial, 100 mcg is 10 units on a U-100 syringe.

Stacks people report

Combinations from guides and community posts, with the reason given.
  • IGF-1 LR3

    Myostatin block plus direct IGF-1 receptor activation. One guide lists 50 mcg follistatin with LR3.

  • CJC-1295

    50 mcg follistatin with CJC-1295 and ipamorelin: myostatin block plus a GH/IGF-1 push. One guide suggests running follistatin alone for a cycle first.

  • Ipamorelin

    GH secretagogues work on a separate pathway, so guides say they stack without overlap.

  • BPC-157

    With TB-500, to help tendons and ligaments keep up with faster muscle growth.

  • TB-500

    With BPC-157, for connective tissue support.

  • Somatropin (HGH)

    Myostatin block with GH for systemic growth signalling, a niche community stack.

Compare Follistatin 344

Evidence and legal status

Evidence: limited human data

No human study has tested injected follistatin protein. The human data are two small gene therapy trials that put the FS344 gene into thigh muscle (6 Becker muscular dystrophy patients, 6 inclusion body myositis patients) and an 11-patient eye-clinic case series of bodybuilders. The rest is animal work: transgenic mice, gene-delivered mice, macaques and pigs.

FDA and WADA

Not FDA approved

No approval, no trial program and not on FDA's compounding lists.

Not FDA approved, and no approved follistatin product exists. Not named on FDA's 503A category lists or on the compounding safety-risk page. Follistatin gene therapy (AAV1.CMV.FS344) has only been tested in small phase 1/2a trials; injected follistatin protein has no trial at all.

WADA 2026 lists follistatin under S4.3, agents preventing activin receptor IIB activation, banned at all times. Doping labs can tell black-market His-tagged FS344 apart from the follistatin your body makes.

WADA: Prohibited

Follistatin 344 questions

What is follistatin 344?

Follistatin is a protein that binds myostatin and stops it from reaching its receptor, which takes the brake off muscle growth. FS344 is one of its spliced forms; after processing it becomes FS315, the version that circulates in blood. In the lab, mice engineered to overproduce follistatin in muscle carried far more muscle, on par with mice lacking myostatin.

Why is it called 344?

344 is the amino-acid count of the precursor protein. It is cleaved into FS315, the circulating form, while FS288 stays bound to tissue. FS344 was picked for gene therapy because FS315 binds activin about 10 times less than FS288.

How much follistatin 344 per day?

Most guides and community reports land at 50 to 200 mcg once a day, with 100 mcg as the default. PeptIQ app users most often log 50 to 100 mcg per shot, with reports up to 200 mcg. One guide warns against going above 200 mcg a day.

How long is a follistatin cycle?

Short. The common pattern is 10 to 30 days on with 3 to 4 weeks off, and many people run a single 1 mg vial over 10 to 20 days and then stop for months. Other guides run 4 to 6 weeks with a 4-week washout, or 8 weeks on and 8 off on training days only.

How much water goes in a 1 mg vial?

Guides use 0.5, 1, 2 or 3 mL of bacteriostatic water. At 1 mL, 100 mcg is 10 units on a U-100 syringe; at 2 mL it is 20 units. Use the calculator for your own numbers.

Does injecting follistatin build muscle?

Unknown. The big results came from genes that make follistatin inside muscle for months or years: mice for over 2 years, macaques with larger and stronger quads, transgenic pigs with more muscle and less fat. No study has tested injected follistatin protein in people, and community reports are mixed, with many users noticing little.

What did the human gene therapy trials find?

Six men with Becker muscular dystrophy got AAV1.CMV.FS344 injected into both thighs. Four walked farther on a 6-minute walk test, by 29 to 125 m, two did not change, and no adverse effects were reported. A 2017 trial in 6 people with inclusion body myositis reported walking gains against untreated patients; a Harvard neurologist called those functional gains unfounded in a reply in the same journal.

Can follistatin affect your vision?

An eye clinic reported 11 bodybuilders with fluid under the retina after injecting whole 1 mg vials under the skin. With one injection the fluid cleared in about 2.3 months; it came back in the 3 who injected again. The authors call follistatin-344 a risk factor. Any change in vision is a reason to stop and see an eye doctor.

Is the vial really follistatin?

Often not. A doping lab tested 17 black-market products: only 9 contained follistatin, and some of the rest held other growth peptides such as MGF or GHRP-2. All 9 real ones were His-tagged FS344, a lab-reagent form, with a high share of clumped oligomers.

Does follistatin affect fertility?

It can in theory, because follistatin suppresses FSH through activin. Trials picked FS344 to limit that, and the Becker gene therapy trial reported no adverse effects. Guides still say to avoid it when trying to conceive.

What is the half-life of follistatin 344?

No human figure exists for injected FS344. Guides quote about 90 minutes, 2 to 4 hours or about 35 hours, without citing a measurement. A Lilly study found native FS315's pharmacokinetics poorly suited to an injected drug; fusing it to an antibody fragment stretched its terminal half-life about 100-fold.

Are there before and after results?

Not controlled ones. No trial has measured injected follistatin in people, so before-and-after photos online are anecdotes, and users report notably inconsistent results.

Is follistatin 344 FDA approved?

No. No follistatin product is approved, and it is not named on FDA's 503A compounding category lists or safety-risk page.

Is follistatin banned in sport?

Yes. WADA lists myostatin-binding proteins such as follistatin under S4.3, banned at all times.

Ask about Follistatin 344

Answers come from this site's pages only, with a link to each source.

Sources

24 sources, each checked by date. Record updated Oct 24, 2026. Numbers are restated in our own words and labelled by where they came from.

Regulatory3

  1. 503A bulk drug substance categories (May 14, 2026)FDA · checked Oct 24, 2026
  2. Certain bulk drug substances, safety risksFDA · checked Oct 24, 2026
  3. WADA Prohibited List 2026WADA · checked Oct 24, 2026

Competitor guide7

  1. Follistatin 344 protocolPathToPeptides · checked Oct 24, 2026
  2. Follistatin-344 dosing guideThe Peptide Catalog · checked Oct 24, 2026
  3. Follistatin 344 dosage guidePeptidesExplorer · checked Oct 24, 2026

Community-reported2

  1. Follistatin community protocolsPeptide Protocol Wiki, via a competitor guide · checked Oct 24, 2026
  2. Performance-enhancing peptides modulating GH-IGF1 axis (Dominikowski 2026)PMC, via a study · checked Oct 24, 2026