Follistatin-315
Also known as: FST-315 · Follistatin 315
A truncated 315-amino acid isoform of follistatin that lacks the heparin-binding domain, giving it a shorter half-life and more localized action compared to Follistatin-344. Still potently inhibits myostatin and activin for muscle growth but with a different distribution profile.
What is Follistatin-315? A truncated 315-amino acid isoform of follistatin that lacks the heparin-binding domain, giving it a shorter half-life and more localized action compared to Follistatin-344. Still potently inhibits myostatin and activin for muscle growth but with a different distribution profile.
How does Follistatin-315 work? Follistatin-315 binds and neutralizes myostatin and activin in tissues, removing the biological ceiling on muscle growth. The lack of a heparin-binding domain means it circulates more freely and has systemic distribution, while Follistatin-344 stays more localized near secretion sites.
Benefits of Follistatin-315: Inhibits myostatin for significant muscle mass increases; More systemic distribution than Follistatin-344; Increases lean body mass; Improves muscle recovery; Bone density enhancement
Follistatin-315 dosage: Research cycles 10-30 days. Systemic distribution differs from FST-344. Very limited human data.
Research status: Research Only
Source: PeptideWiki — https://www.peptide-wiki.net/peptides/follistatin-315
Mechanism of Action
Follistatin-315 binds and neutralizes myostatin and activin in tissues, removing the biological ceiling on muscle growth. The lack of a heparin-binding domain means it circulates more freely and has systemic distribution, while Follistatin-344 stays more localized near secretion sites.
Benefits
- Inhibits myostatin for significant muscle mass increases
- More systemic distribution than Follistatin-344
- Increases lean body mass
- Improves muscle recovery
- Bone density enhancement
Side Effects & Risks
- Limited long-term human safety data
- Joint stress from rapid muscle growth
- Injection site reactions
- Potential hormonal effects via activin inhibition
Storage & Reconstitution Guide
Storage Temperature
-20°C (lyophilized)
24 months (lyophilized), 28 days (reconstituted)
Reconstitution Solvent
Bacteriostatic water (BAC water)
Swirl gently — do not shake or vortex
Handling Notes
Protect lyophilized peptide from moisture and light. Once reconstituted, keep refrigerated. Discard if solution becomes cloudy or discolored. Use insulin syringe for precise dosing.
Step-by-Step Reconstitution
Gather supplies
BAC water, insulin syringe, alcohol swabs, vial
Disinfect tops
Swab rubber stoppers of both vials with alcohol
Draw BAC water
Pull desired mL of BAC water into syringe
Inject slowly
Inject BAC water down the side of the peptide vial, swirl gently to dissolve
Research Protocol
- Dose Range
- 50–100 mcg
- Frequency
- Once daily
- Cycle
- 10-30 days
- Routes
- subcutaneous injectionintramuscular injection
- Notes
- Research cycles 10-30 days. Systemic distribution differs from FST-344. Very limited human data.
Legal & Regulatory Status
Sold for research purposes only. Not for human use. Laws vary by country.
Commonly Stacked With
View all peptide stacks →External Resources
PeptideWiki Research Team
Evidence-based research data sourced from PubMed and ClinicalTrials.gov · Last updated: February 25, 2026
Frequently Asked Questions About Follistatin-315
What is Follistatin-315?▾
A truncated 315-amino acid isoform of follistatin that lacks the heparin-binding domain, giving it a shorter half-life and more localized action compared to Follistatin-344. Still potently inhibits myostatin and activin for muscle growth but with a different distribution profile.
What are the benefits of Follistatin-315?▾
Inhibits myostatin for significant muscle mass increases
What are the benefits of Follistatin-315?▾
More systemic distribution than Follistatin-344
What are the side effects of Follistatin-315?▾
Limited long-term human safety data
What is the recommended dosage for Follistatin-315?▾
Research cycles 10-30 days. Systemic distribution differs from FST-344. Very limited human data.
How long should a Follistatin-315 cycle last?▾
10-30 days
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