Understand the source comparison
Follistatin 344 vs Follistatin 315: Which to Choose?
This question comes up frequently, and the answer is straightforward. For injectable use, FS-344 and FS-315 are functionally equivalent because FS-344 converts to FS-315 in your bloodstream. Amino acids Stability as recombinant Higher Lower Availability In viv
No winner is assigned.
This page preserves a source comparison for education. It does not add a rating, recommendation or clinical judgment.
- This question comes up frequently, and the answer is straightforward. For injectable use, FS-344 and FS-315 are functionally equivalent because FS-344 converts to FS-315 in your bloodstream.
- Amino acids
- Stability as recombinant
- Higher
- Lower
- Availability
- In vivo conversion
- Converts to FS-315
- Already active form
- Myostatin binding affinity
- High (direct + via FS-315)
- High
- Tissue distribution
- Systemic (via FS-315)
- Primarily muscle/circulation
- Research base
- Extensive (gene therapy studies)
- Limited as standalone
- Recommended for injection
- Yes (standard choice)
- Acceptable if available
- The practical reason FS-344 dominates the market: it is easier to produce as a stable recombinant protein and has the larger evidence base from gene therapy research. FS-315 is the bioactive downstream product, but injecting the precursor (FS-344) and letting your body do the conversion is the established approach.
- If a vendor offers "follistatin 315" at a significantly lower price, verify purity and source carefully. The less common product carries higher risk of quality issues simply due to smaller production volumes and less standardized manufacturing.