It is the most-bought form. Follistatin 344 (FST-344) is the precursor isoform that the body cleaves into circulating FS-315 and tissue-bound FS-288, and it is what most online vendors actually ship.
That alone does not make it a finished drug. The dose ranges below come from community protocols and gene-therapy extrapolation, not placebo-controlled human trials.
Key takeaways
- Common community dose is 100 mcg subcutaneously per day for a 10 to 30-day cycle, then 4 to 8 weeks off.
- Recombinant FST-344 has a ~90-minute plasma half-life, so injections need to be daily or split.
- FST-344 is a precursor; FS-315 is the systemic form, and FS-288 stays bound to tissue locally.
- Human gene therapy with AAV1-FS344 produced 29 to 125 meters of 6-minute walk gain in Becker muscular dystrophy.
- 11 bodybuilders developed central serous chorioretinopathy after injecting full 1 mg vials.
- Real recombinant follistatin from biotech suppliers runs above $4,500 per 1 mg, so cheap vendor pricing is a red flag.
Follistatin 344 dosage table
Start with the numbers. These are the dose tiers most repeated by experienced users and clinics that work with the peptide.
| Tier | Daily dose | Frequency | Route | Cycle length | Off period |
|---|---|---|---|---|---|
| Conservative starter | 100 mcg | 1x daily | Subcutaneous | 10 to 14 days | 6 to 8 weeks |
| Standard community | 100 to 200 mcg | 1x daily | Subcutaneous or intramuscular | 10 to 30 days | 4 to 8 weeks |
| Pre-workout split (FST-344 alt) | 50 mcg | Training days only | Intramuscular | 6 to 8 weeks | 8 weeks |
| Aggressive (higher risk) | 200 to 300 mcg | 1 to 2x daily | Subcutaneous | 20 to 30 days | 8 weeks minimum |
That is the practical floor and ceiling. For deeper reconstitution math and dose-by-goal splits, read the follistatin dosage breakdown.
For the bigger pathway picture, see what follistatin is.
What FST-344 actually is
It is a precursor isoform. Follistatin 344 refers to the 344-amino-acid sequence the body produces before cleavage into the two functional adult isoforms.
FS-344 itself is the form used inside the AAV1-FS344 gene therapy program, because letting muscle cells express the precursor lets the body generate both FS-315 (which circulates) and FS-288 (which binds heparan sulfate on tissue) in the right ratios.
That matters for the peptide market. A vial labeled "follistatin 344" is being sold on the assumption that injected FS-344 will be cleaved the same way in vivo. It is the working theory of every community protocol, not a finished pharmacokinetic dataset.
How it differs from FST-315 and FS-288
The functional split is real. FS-315 is the dominant blood-borne form and is what shows up on a serum follistatin test, while FS-288 is locked to cell surfaces in tissue.
| Feature | FST-344 | FS-315 | FS-288 |
|---|---|---|---|
| Length (aa) | 344 (precursor) | 315 | 288 |
| Location | Cleaved into the others | Circulating in serum | Bound to heparan sulfate on cells |
| Binding profile | Source of both adult forms | Activin, myostatin, BMPs (systemic) | Activin and myostatin (local) |
| Half-life issue | Cleaved rapidly in vivo | Short circulating half-life | Effectively tissue-tethered |
| Typical use | Underground peptide and gene therapy | Sold as "FST-315" peptide too | Rarely sold direct |
Most articles that frame FST-315 vs FST-344 as a head-to-head ignore that the body makes both from the same precursor. The choice between products is usually downstream of vendor identity, not biology.
What human evidence supports it
This is the honest middle. The strongest human data is from gene therapy, not subcutaneous protein.
Mendell and colleagues delivered AAV1.CMV.FS344 to six Becker muscular dystrophy patients at 3 to 6 × 10^11 vector genomes per kilogram per leg. Four of six gained between 29 and 125 meters on the six-minute walk test at 180 days, with reduced fibrosis on biopsy.
A 2017 follow-up in sporadic inclusion body myositis showed a 56-meter gain per year in the treated group versus a 25-meter decline in untreated controls (p = 0.01), with no treatment-related adverse events. A separate 2017 critique by Hanna and colleagues warned that prednisone and prescribed exercise in the same cohort could account for much of the gain.
Macaque data from 2009 added support. Six cynomolgus monkeys received bilateral quadriceps injections of AAV1-FS344 at 1 × 10^13 vector genomes total, with about a 15% quadriceps circumference increase at 8 weeks and sustained gains out to 60 weeks.
Direct injectable peptide trials in humans are effectively absent.
What happens during a cycle
Most users feel little day to day. Strength changes show up slowly and modestly, and pump and connective-tissue stiffness are common early subjective notes.
A realistic timeline from community logs and clinical work:
- Days 1 to 7. No visible change. Mild injection-site reactions are normal. Track sleep and appetite for any unusual rise.
- Days 7 to 14. Strength on key lifts may creep up. Muscle fullness is the most common subjective signal.
- Days 14 to 30. Lean-mass changes can become visible at this point, mostly when training volume is also high. Forum users report 2 to 5 pounds in a 30-day cycle as a believable range.
- Off period (4 to 8 weeks). Satellite-cell integration continues. Some strength gains persist; cosmetic gains soften without continued training stimulus.
Anyone promising 15 to 25 pounds in three weeks is selling, not measuring. Earlier forum reports of that magnitude were uncontrolled, often stacked with other compounds, and not reproduced.
Side effects and safety signals
Two issues lead the list. The first is dose-dependent eye risk; the second is FSH and reproductive disruption.
Central serous chorioretinopathy. A 2020 case series in Springer Ophthalmology documented 11 male bodybuilders who developed CSCR after subcutaneous follistatin-344 use. All injected full 1 mg vials at once, roughly ten times the starting community dose. Vision impairment resolved over two to three months in most cases.
FSH suppression and fertility. Follistatin was first isolated as FSH-suppressing protein. Sustained myostatin and activin inhibition can reduce FSH levels (reported up to 75% drops in animal work), with theoretical effects on fertility and reproductive hormone patterns.
Other reported issues include injection-site reactions, mild flu-like symptoms, modest LDL increases, and theoretical cardiac concerns based on myostatin's role in heart energy homeostasis. For deeper detail, see follistatin side effects.
The vendor reality
This is where most readers get burned. Real recombinant human follistatin from biotech suppliers runs above $4,500 per 1 mg, while underground vendors routinely list "follistatin 344" at $50 to $150 per 1 mg vial.
The math does not work. Either the product is not what it claims, the purity is poor, or it has been replaced with a cheaper peptide. Independent testing has found mislabeled vials containing MGF or GHRP-2 instead of follistatin.
Trust checks that actually help:
- A real certificate of analysis with HPLC and LC-MS data, not just a PDF logo
- Independent third-party purity testing above 98%
- Clear sequence and isoform identity on the COA
- Vendor willingness to identify lot numbers and storage conditions
- Pricing that admits the underlying cost of a fragile glycoprotein
If a vendor cannot pass those, the FST-344 claim is irrelevant. We cover the buying side in where to buy follistatin.
Who FST-344 actually fits
The honest fit is narrow. It is most defensible for advanced lifters who have already optimized training, protein, sleep, and creatine, and who accept the regulatory and safety unknowns.
Poor fits include:
- Beginners still gaining on standard programming
- Anyone on FSH-sensitive fertility plans
- People with a history of central serous retinopathy or eye disease
- Anyone unwilling to pay for properly tested material
- Athletes subject to WADA testing, which now screens for follistatin and myostatin-pathway agents
For the broader category, see best myostatin inhibitor and the myostatin inhibitor peptide guide.
Sources and notes
Built from DuckDuckGo and Bing SERP review, full competitor crawls, and the underlying clinical literature:
- Follistatin 344 Peptide — Jay Campbell
- Follistatin 344: Dosage, Buying, Benefits, Uses — Muscle and Brawn
- Follistatin 344 Dosage Guide — PeptideWiki
- Follistatin-344 Dosing: 50 mcg Pre-Workout Protocol — The Peptide Catalog
- Follistatin-344 (FST-344): Research Evidence — Peptide Insight
- Phase 1/2a follistatin gene therapy for Becker muscular dystrophy
- Follistatin gene therapy for sporadic inclusion body myositis
- Central serous chorioretinopathy associated with high-dose follistatin-344
Frequently Asked Questions
What is the typical follistatin 344 dose?
100 mcg subcutaneously once a day for 10 to 30 days is the most repeated community protocol, followed by 4 to 8 weeks off. Some users split it intramuscularly or front-load 50 mcg on training days only.
How long is a follistatin 344 cycle?
Most cycles run 10 to 30 days. Longer cycles add cost without clear added benefit, and they extend exposure to FSH suppression and other systemic effects.
How much muscle should I expect from one cycle?
A realistic ceiling is 2 to 5 pounds of mostly lean mass over 30 days, paired with hard training. Higher claims usually involve other compounds or short-term water and glycogen changes.
Is follistatin 344 safe?
Short, low-dose cycles in gene-therapy trials were well-tolerated. Subcutaneous peptide use has reported central serous chorioretinopathy at high single doses, plus FSH suppression and unknowns around cardiac myostatin signaling.
FST-344 vs FST-315: which is better?
FST-344 is the precursor your body cleaves into FS-315 and FS-288. Vendor product choice matters less than purity, identity testing, and dose, since both end up as the same downstream isoforms.
Is follistatin 344 legal?
No follistatin product is FDA-approved for human use in 2026. Possession of research peptides exists in a gray zone, and athletes face explicit WADA prohibition under S4 hormone and metabolic modulators.
This article is for educational purposes only and is not medical advice. Talk with a licensed healthcare professional before using any peptide or experimental therapy, particularly if you have eye disease, fertility concerns, cardiac history, or take prescription medications.
