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Follistatin 315
Research Use
Also known as FS-315
Function
Primary
Muscle hypertrophy (research)
Mechanism
Circulating follistatin isoform with a heparin-binding domain removed; binds activin and myostatin systemically with a longer plasma residence than FS-344.
Evidence
Pre-clinical / Observational
Research
Animal gene-therapy and protein data
Dosing
Range
100 mcg/day (reported research use)
Frequency
Daily for 10–30 days
Route
Subcutaneous
Administration & Technique
Subcutaneous (SubQ)
Default route for most research and therapeutic peptides — best absorption for reconstituted powder.
Device31G × 5/16" insulin syringe (U-100). 100 units = 1 mL.
TechniquePinch skin at abdomen (2" from navel), outer thigh, or love handle. Insert at 45–90°. Rotate sites daily to prevent lipohypertrophy. Alcohol-swab site, air-dry, inject slow, hold 5 sec.
Injection & Application Sites
Front
Back
Subcutaneous (SubQ)
- Abdomen — 2 in (5 cm) away from the navel, either side. Fastest, most consistent SubQ absorption.
- Flank / love handle — Lateral fat pad above the hip. Good rotation site when the abdomen is tender.
- Outer thigh — Upper outer quadrant, a hand-width below the hip. SubQ pinch at 45°.
Diagram is a general illustration, not a medical instruction. Rotate sites every injection, keep 1 in (2.5 cm) between recent sites, and avoid scars, moles, bruises and the navel area.
Cycling
Short 10–30 day blocks reported; long-term use uncharacterized.
Timing & Interactions
When to take
No strict time-of-day requirement. Dose consistently at the same time daily and rotate injection sites. Follow the per-peptide dosing section above.
Do not combine with
- ·Avoid stacking with peptides that share the same receptor or mechanism without clinical guidance.
- ·Avoid combining with alcohol or immunosuppressants unless cleared by a clinician.
Complements
- ·Most peptides pair safely with baseline nutrition, sleep, and resistance training.
Storage & Reconstitution
Powder (Pre-Reconstitution)
Lyophilized powder: refrigerate 2–8°C for up to 24 months, or freeze at –20°C for extended storage. Keep sealed, desiccated, and protected from light.
After Reconstitution
After reconstitution with bacteriostatic water, refrigerate at 2–8°C and use within 28 days. Discard if cloudy, discolored, or precipitated.
Notes
Do not freeze after reconstitution — freeze/thaw cycles degrade most peptides.
Reconstitution Calculator
Concentration
2.50 mg/mL
Volume per dose
0.100 mL
Insulin syringe
10.0 units (U-100)
1 mL = 100 units on a standard U-100 insulin syringe. Draw to the nearest 0.5 unit and confirm dosing with a clinician before injection.
Your Notes
Your Notes
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Benefits
- ·Systemic myostatin suppression
- ·Lean-mass increase in animal models
Risks
- ·Unknown effects on ovarian/pituitary activin signaling
- ·Possible fibrosis
- ·Purity concerns
Contraindications
- ·Active malignancy
- ·Pregnancy or fertility treatment
- ·Endocrine disorders
Regulatory
Research chemical — WADA-banned
Veterinary Use (Pets)
No established veterinary protocol for Follistatin 315. Consult a licensed veterinarian before considering off-label use in any species.
Full veterinary reference →Functional Groups
Cited Works
- Lee SJ. Quadrupling muscle mass in mice by targeting myostatin & follistatin. PLoS ONE. 2007;2:e789.source