Myostatin/activin-binding protein sold as 1 mg vials; about half of tested vials held no follistatin.
Safety tier
Avoid
strict bar
Positive
44%
of 10 reports
Per month
≈ €180–450
estimate
Rank
#46
of 61 research peptides
At a glance
Onset
Unknown: there are no human pharmacokinetic data for injected follistatin protein. Users claim effects within days, which is not plausible for muscle growth.
Lasts
Unknown for the protein (users quote anything from 90 minutes to 12 hours); gene therapy is designed to last months or longer.
Access
Grey market
Strict case
Blocks myostatin and activin signalling (FSH axis, angiogenesis, glucose) with no human safety data for the injected protein; vials often hold other drugs.
Best effects
Claimed strength and 'pump' (confounded by steroids, GH secretagogues and training) · muscle growth in animal and gene-therapy studies
Downsides
Swollen, painful injection-site lumps lasting days · flu-like symptoms, fatigue and mental fog · very expensive per mg · no measurable effect for many users
Typical use
Users: 50-100 mcg/day subq or IM for 10-20 days, some up to 1 mg/day. No human dose has been studied for the protein.
Stacked with
Stacked with
Testosterone and other anabolic steroids: Most glowing reports come from people on TRT or a steroid cycle, so the steroid explains the gain. · Tesamorelin / ipamorelin or IGF-1 LR3: Run alongside GH secretagogues or IGF-1 LR3 in 10-20 day 'myostatin' blocks.
Safety
Watch
Product: in an anti-doping lab test only 9 of 17 black-market 'follistatin 344' vials contained follistatin; some held GHRP-2 or mechano growth factor instead (Reichel 2019) · Activin/FSH axis: follistatin neutralises activin, which drives pituitary FSH; mice overexpressing it have reproductive defects · Angiogenic in vivo (rabbit cornea), strongly so together with bFGF: a theoretical route to feeding tumour vessels · Higher circulating follistatin tracks with type 2 diabetes, heart failure and death in a 4,733-person cohort (association, not proof) · A related myostatin/activin trap, ACE-031, was halted in a pediatric trial for nosebleeds and telangiectasias
Tier by safety barStrict AvoidBalanced AvoidEvidence only Caution
Seen harm0 of 3
Mechanism2 of 3
Data gap3 of 3
Silent harm3 of 3
Product3 of 3
Never if
Pregnancy, breastfeeding or trying to conceive (follistatin suppresses FSH; overexpressing mice have reproductive defects) · Active or past cancer (angiogenic in vivo) · Diabetes or prediabetes · Under 18
The angiogenic pathway points at theoretical support for tumour vessels, which is silent and delayed (3 under the rubric). Fertility and glucose effects would build up but show on hormone or glucose tests (a 2); injection-site and flu-like reactions are immediate. Kozian et al. 1997: follistatin is angiogenic in vivo ↗
Eleven reports: eight on grey-market vials and three on offshore gene therapy. The four glowing or positive vial reports (10 lb in 20 days, a 40 lb deadlift jump in a week, 'super soldier serum') all come from people also on testosterone, tesamorelin/ipamorelin or a hard training block, or describe gains too fast to be muscle. The others get sore, swollen injection sites lasting days, flu-like symptoms, fatigue and fog, or nothing. Replies in these threads overwhelmingly call it a waste of money. Of three gene-therapy patients (offshore clinics in Mexico and Honduras; one paid $25,000), two noticed nothing and one, who gave no details, called the results impressive. Felt nothing: Of 8 reports on the vials, 1 says it does nothing and 3 describe only injection-site or flu-like reactions; 2 of 3 gene-therapy reports felt nothing..
I did my Follistatin 344 gene therapy at Roatan with Dr.Terry it’s been 3 months for me now since, but I haven’t noticed any effects yet.
NothingLongevity · Injection · 3 months since treatment
follistatin gene therapy on Roatán (Honduras), not the peptide
Studies
Evidence
Animal only — data for the protein alone; the only human data are 12 patients given intramuscular AAV1.FS344 gene therapy for muscle disease, which says nothing about injecting the protein
Caveat
FS344 is a roughly 38 kDa protein isoform (the precursor of circulating FS315), not a short peptide; whether a lyophilised research vial holds intact, active protein is unverified, and the anti-doping test found many held none. The gene-therapy results come from muscle-disease patients and a different delivery, and the offshore clinics' own outcome data are unpublished or self-reported.
Reichel et al. 2019: detection of black-market follistatin 344in-vitro · n=17 · 2019 Only 9 of 17 products labelled follistatin contained it, all as His-tagged FS344 with heavy oligomerisation; others held growth-promoting peptides such as MGF or GHRP-2.
The peptide's chain of amino acids from its start (the N-terminus) to its end, one bead and one letter for each: A alanine, C cysteine, D aspartic acid, E glutamic acid, F phenylalanine, G glycine, H histidine, I isoleucine, K lysine, L leucine, M methionine, N asparagine, P proline, Q glutamine, R arginine, S serine, T threonine, V valine, W tryptophan, Y tyrosine. A modification such as an N-acetyl cap or a C-terminal amide changes how long it lasts in the body. Length tells related peptides apart, from a two-residue dipeptide like carnosine to a 43-residue protein like thymosin beta-4, and predicts neither effect nor safety.
Report grades
Every first-hand Reddit or X report is graded on its own, from glowing through positive, mixed, nothing and negative to bad reaction, and the bar shows how those grades split. Posts that look vendor-adjacent stay on the peptide's page but are left out of the counts.
GlowingPositiveMixedNothingNegativeBad reaction
% positive
The share of a peptide's graded Reddit and X reports that are glowing or positive, vendor-adjacent posts left out. A peptide with few reports is pulled toward the average of all reports, as if it had eight average ones besides its own, so two glowing posts cannot top the list. Peptides rank by this figure, those with no graded report yet after those with one, and Avoid ones after every other entry.
Researcher estimate
No first-hand report of this peptide has been graded yet, so the figure is the researchers' own rating out of 10 from what they read about it. It ranks after every peptide with graded reports until its own arrive.
Safety tier
Each peptide is tiered Clean, Caution or Avoid from its five risk axes under the chosen safety bar. An Avoid peptide carries a real risk of harm, a plausible route to serious harm rather than mere unpleasantness, so it stays listed with the reason but ranks behind every other entry, however good its reviews.
Safety bar
The safety bar sets how much risk it takes to rate a peptide Avoid. Strict: out on any serious mechanism with little human data, or any documented serious harm. Balanced: out on documented serious harm (unless it is obvious, reversible and from a regulated product), or a serious mechanism whose harm would be silent with no human data at all. Evidence only: out only on documented serious harm in humans that is lasting, delayed or from grey-market product.
Seen harm
Documented serious adverse events in humans, from 0 for none despite real exposure to 3 for deaths or several well-documented serious harms. Serious means a hospital or emergency visit or harm lasting weeks, so a headache or a bad night does not count.
Mechanism
A plausible biological route to serious harm at the doses people use, such as growth-factor signalling, hormone-axis suppression, heart or blood-pressure effects or immune activation. It runs from 0 when none is known to 3 when a dangerous pathway has been shown in living animals.
Data gap
How little human safety data exists for the molecule actually sold, from 0 for an approved drug with large trials and years of use to 3 for no human safety data at all. A modified analogue does not inherit its parent's trials.
Silent harm
Whether the feared harm would show quickly or stay hidden, from 0 when it is obvious and goes on stopping to 3 when it is silent and delayed, like tumour promotion or slow organ damage. User reports cannot reveal a harm that takes years to appear, so a high score here limits what good reviews can tell you.
Product
The risk of what people actually buy, from 0 for a regulated pharmacy or supplement product taken by mouth or on the skin to 3 for a grey-market injectable. In one dataset of 6,441 grey-market samples, 42–71% failed basic quality criteria and 15% carried endotoxin; taken by mouth or in the nose, a pack avoids the injection risks.
Evidence
The strongest kind of study behind the peptide's effects, from an approved drug through human controlled trials and small human studies to animal work or nothing of its own. Animal results often fail to carry over to people.
Access
How people get it: as an approved drug, a compounded prescription, an over-the-counter supplement or from the grey market, where nobody checks the vial. The channel decides both the legal position and the risk of a bad batch.
Price per month
Thirty days of the typical dose, from its low end to its high end, priced at the listing a careful buyer would choose: in stock, from a shop scoring 4 of 5 on trust (third-party tested where no score is set), failing that 3, a pure pack before a blend, a European shop first, then the cheapest per mg. The range is the dose's, not the shops'. A per-dose amount counts once a day unless the dose says otherwise. Prices are in euros at ECB rates of 2026-10-29, before shipping; the shop table keeps each listing's price per mg, per gram for bulk supplements. Where no listing can be priced the researchers' own estimate stands in, and says so.
Dose users report
The middle half of the daily doses stated in at least five first-hand reports, vendor posts left out. Where its middle sits more than twice above or below the declared dose, the month is priced at it as well, since what people take is what they pay for.
Shop trust
Each shop's trust on a 1–5 scale, read from its testing and its reputation: 1 for serious red flags (fabricated COAs, scam reports, impersonation, a closed shop), 2 for no public testing, a new shop or active complaints such as seized parcels, 3 for its own COAs or a short track record, 4 for verified third-party testing or a strong reputation, and 5 for third-party batch reports that name the shop, with years of good independent reputation. A shop without a score counts third-party batch testing as 4, its own COAs as 3 and no public tests as 2.
Best value
Within a category or a goal, a peptide that no other beats on both counts: none is rated more positively for the same or a lower monthly price, and none costs less for the same or a higher rating. The chart joins these into the best-value line; the cheapest of them and the best-rated of them both make it, so the line spans the trade-off from cheap to best. Avoid entries never count, and a peptide needs both a % positive and a price to be compared.
Testing
Whether the shop publishes lab results: third-party tested means an independent lab checks each batch, own COA means the shop's own certificate of analysis, and no public tests means neither. A certificate shows purity, not safety.
Added peptide
Some packs sold under one peptide's name hold a second one, such as 5 mg GHK-Cu in a nasal kit, stated only in the description. Sprayed in the nose or injected it reaches the blood like an injection, so it carries the risk of that route and is tiered as the injectable form, whatever its tier on the skin. A pack whose page gives no contents list may hold more than its name.