Skip to content
Limited human dataNot FDA approved

Follistatin 344 side effects

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

Updated 24 sources

7 side effects reported for Follistatin 344: 2 from studies and labels, 5 from users and guides. 2 come with the ways people manage them.

Follistatin 344 overview

Side effects reported in studies and labels

Rates as each trial or label states them. A rate from one trial does not carry over to research-grade vials or other doses.

From trials and regulators2

Clinical studies 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

Side effects users and guides report

What people post and what dosing guides list. These are reports, not measured rates.

From users and guides5

Community reports, competitor and vendor guides, media.

  • 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

Who should avoid it, and what not to combine

  • 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.

How much is known

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.

Sources for these side effects

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

Regulatory1

  1. WADA Prohibited List 2026WADA · checked Oct 24, 2026

Competitor guide5

  1. Follistatin 344 dosage guidePeptidesExplorer · checked Oct 24, 2026
  2. Follistatin-344 dosing guideThe Peptide Catalog · checked Oct 24, 2026
  3. Follistatin-344 dosage guideBodyHackGuide · checked Oct 24, 2026
  4. Follistatin dosing protocolsPeptide Protocol Wiki · checked Oct 24, 2026

Community-reported1

  1. Follistatin community protocolsPeptide Protocol Wiki, via a competitor guide · checked Oct 24, 2026

Back to the full Follistatin 344 page for dosing, the vial chart and storage.