Follistatin: Dosage & Administration

The most important practical fact about follistatin dosing: there are no human clinical trials of injectable follistatin protein for muscle growth. The widely-cited Mendell et al. 2015 Phase 1/2a follistatin trial used AAV-based gene therapy (a single localized injection of viral vector that produces follistatin continuously in muscle tissue), not injectable follistatin protein.^[2] The dose ranges below come from the research-peptide community and animal studies, not formal clinical protocols.

This matters for safety expectations: gene therapy produces local, sustained, predictable follistatin expression at modest concentrations. Injectable follistatin protein produces a brief systemic pulse with very different pharmacokinetics — and an entirely uncharacterized human safety profile. Anyone using injectable follistatin should treat the dosing below as a starting framework, not a validated clinical protocol.

Form	Dose	Route	Frequency	Cycle
Follistatin-344 (most common)	100–200 mcg	SC	Once daily	10–30 days
Follistatin-344 (higher)	200–500 mcg	SC	Once daily	10–30 days
Follistatin-315 (less common)	100–200 mcg	SC	Once daily	10–30 days

Follistatin-344 (FS-344) is the precursor isoform — once administered it is cleaved into FS-315 (the primary circulating form) and FS-288 (tissue-bound form). Using FS-344 gives both isoforms; using FS-315 directly gives only the circulating isoform. Most research protocols use FS-344.

Starting at 100 mcg/day for the first week to assess tolerance is the safer protocol given the lack of human data. Effects on muscle protein synthesis are theorized to accumulate over a cycle rather than appear acutely.

Follistatin is a glycoprotein (~37 kDa), not a small peptide. It is substantially more fragile than typical research peptides and requires careful handling.

Technique

• Use bacteriostatic water (benzyl alcohol-preserved sterile water).
• Inject BAC water gently down the side of the vial — do not blast directly onto the protein powder. Mechanical force from a direct stream can denature the protein.
• Do not shake. Swirl gently if needed. Shaking creates foam and damages protein structure.
• Allow 5–10 minutes for the powder to dissolve naturally. Patience matters more than agitation.
• Check the solution after reconstitution: should be clear and colorless. Discard if cloudy, particulate, or has foamy residue.

Example: 1 mg vial

• 1 mg vial + 1 mL BAC water = 1 mg/mL (1,000 mcg/mL). 0.1 mL (10 units) = 100 mcg.
• 1 mg vial + 2 mL BAC water = 500 mcg/mL. 0.2 mL (20 units) = 100 mcg. More dilute = easier to measure.

Use the peptide calculator for exact units. See the reconstitution guide for general technique.

Timing

Follistatin does not have a strict timing requirement related to meals (unlike GH secretagogues). Most protocols inject at a consistent time each day — morning, post-workout, or bedtime are all reasonable.

Cycle length

• Standard cycle: 10–30 days of daily injection.
• Off cycle: 30–60 days off between cycles is the typical research-community pattern.
• Total annual exposure: 3–4 cycles per year is the upper end of conservative use given the lack of long-term safety data.

Stacking

• With GH secretagogues (CJC-1295 + ipamorelin): additive but not synergistic. Both pathways promote muscle protein synthesis independently.
• With IGF-1 LR3: theoretical additive anabolic effect; combined IGF-1 / myostatin-inhibitor stacks are reported anecdotally but carry compounded safety concerns.
• With MK-677 (ibutamoren) or other SARMs/PEDs: outside the scope of this site's recommendations; legal status and safety vary by region.

Follistatin requires more aggressive cold-chain handling than typical research peptides:

• Lyophilized vials: -20°C or colder for long-term storage. Refrigerator (2–8°C) is acceptable for shorter-term but not optimal.
• Reconstituted solution: refrigerate at 2–8°C. Use within 7–14 days. Follistatin is substantially less stable than small peptides like BPC-157 or ipamorelin in solution.
• Avoid room temperature exposure as much as possible. Even brief warm-ups during transport can affect potency.
• Avoid freeze-thaw cycles with the reconstituted solution. Aliquot into smaller portions if needed.
• Protect from light.

For broader storage rules, see the peptide storage guide.