FGL dosage and evidence
Written by Aaron CuhaReviewed Sep 2026
The short answer
FGL is a peptide from a protein that helps nerve cells stick together. It has been studied in rats for memory and brain protection.
Evidence grade for FGL: Animal or lab only. The rule: only animal or lab studies on this page. No study in people yet. The sum on this page: 3 animal studies, no human study. A grade counts how much has been done to people, not whether it works.
- People given it
- 0
- Human studies
- 0
- Found nothing
- 0
Dose
No human dose established
No published study on this page has given this compound to people and reported a result.
3 animal studies, no human study
3 effects reported, 2 unwanted, 1 wanted, by people using it, not a trial
Goal pages: Brain, memory and mood
In plain English
In plain English, from Aaron
This is how I would explain it to a friend. The evidence, with the numbers, is further down the page.
FGL is a small piece of NCAM, a protein that helps nerve cells stick together and talk. It is meant to help the brain form new connections and to protect nerve cells. It is experimental and not approved.
What people take it for
- Better memory.
- Protecting the brain as it ages.
- Pairing with dihexa, which people online often do.
What studies in people showed
Human evidence is minimal. Since nobody can patent it, nobody is likely to pay for a big study in people. In rats, a dose after training gave long-lasting memory gains. It helped new nerve connections form. It protected nerve cells after their blood supply was cut, in a dish and in live animals. In rats given a piece of the Alzheimer's protein amyloid, it cut brain damage and memory problems.
What people report
Reports, not study results
The good
- Almost nobody online describes a clear benefit. Most of what is written is theory, not experience.
The bad
- There are no side effect reports, but there are also no reports of long use. That silence says nothing about safety.
- Forum members warn against taking it at the same time as dihexa. That warning is theory. Nobody reported an actual harm.
Where these come from: Nootropic Stacks and Brain Health threads on LongeCity, found by site-restricted search, September 2026. The discussion is very thin. The study results are from the animal studies on this page.
My bottom line
This is rat data and forum theory. That is not enough to put it up your nose. I would not.
An opinion, not a finding. I am a coach, not a doctor.
What it has been measured to do
What people using it report
Real people telling you what happened to them. Nobody checked it, and the people who post are not a fair sample, so it cannot prove anything works. It is still the best guide on this page to what people actually do with FGL, what they expect, and what goes wrong. The full account, including the negative reports, is below.
Animal and lab work, not yet tested in people
Real results, but from animals or cells, not people. What works in a mouse often does not work the same way in a person. Nobody can patent this, so nobody would ever earn back the cost of a study in people. That is usually why there is none.
- Memory and thinking2 animal or lab studies
35 of the 36 indexed goals have no study of any kind behind FGL
No study in people, animals or cells on this page reports a result for these. That does not prove FGL does nothing for them. It does mean anything you have heard about FGL and one of these did not come from a study cited here.
Show full evidence
What is FGL?
FGL is a peptide from a protein that helps nerve cells stick together. It has been studied in rats for memory and brain protection.
FGL is a small piece of NCAM, a protein that helps nerve cells stick together and talk. It copies how NCAM switches on the FGF receptor. All of the evidence is from animals. Human evidence is minimal, so it is experimental and not approved. In rats, FGL given after training gave long-lasting memory gains and helped new nerve connections form. It protected nerve cells after a loss of blood flow, both in a dish and in live animals. In rats given a piece of amyloid, the Alzheimer's protein, shots of FGL cut brain damage and memory problems. That mix of memory, brain wiring and protection is why it drew interest for ageing and brain disease.
How does FGL work?
It switches on the FGF receptor by copying part of NCAM. That helps nerve cells form connections and survive.
What do people who took FGL report?
This is what real people say happened to them, good and bad. Nobody measured it. A report cannot tell a real effect from the lift people get just from expecting it to work, from a diet or training change made at the same time, or from what was really in the vial. We still put it near the top. It is the next best thing to a study in people: what happens when real people use it, including what goes wrong.
- The body of discussion is very small, a handful of people in brain supplement threads, and it is overwhelmingly guesswork rather than experience. Most of what is written is theory about how brain cells signal each other, not anyone describing what happened to them.
- Where people do describe use, the nasal route at a starting amount of around half a milligram is what appears, and the human tolerability work people cite involves considerably larger nasal amounts.
- It is discussed almost exclusively next to dihexa, with claims that it is the stronger of the two and that the pair together is greater than either. No account in the discussion isolates it.
- The one real caution raised is against combining the two at once, on a theoretical concern about cell death, with the suggestion that one should be fully cleared before the other is started. That is theory from forum members, not a harm anyone saw.
- There are no no-effect reports, no side effect reports and no accounts of extended use. For a compound with essentially no human exposure outside a small early trial, that absence means the discussion has nothing to say about safety, not that the compound is safe.
Sources: Nootropic Stacks and Brain Health threads on LongeCity covering FGL and its comparison with dihexa, found by site-restricted search, September 2026. The discussion is thin and the entry is short and heavily qualified for that reason. Nothing above is attributed to any specific post and no post is reproduced.
The evidence, in charts
Fig. 1a · how many people
0people have taken this in any study cited here
0 people · 0 studies in people
What this page cites instead is 3 animal studies. None of them gave the compound to a person.
Counted from the list of sources on this page. We draw this chart only when a study in people is cited. An empty one is the answer, not a gap in the page.
Fig. 1b · evidence mix
None of the 3 sources here are studies in people.
- Animal study · done in animals3100%
Counted from the list of sources on this page. It counts only what we cite, so there may be more studies out there. A review counts once, however many studies it sums up.
Fig. 2 · evidence over time
The studies cover 3 different years, 2004 to 2007, counted from the list of sources on this page. The newest source on file is from 2007, more than five years ago. Research on it may have gone quiet.
Fig. 3 · legal status at a glance
US
Not approved
UK
Not approved
AU
Not approved
CA
Not approved
Not approved in any of the four countries shown. This is what the law says, not a verdict on the science. See Legal status below for the full text and any notes.
Fig. 4 · how much does what
Nobody has tested different amounts in people
This chart would show how the effect changes as the amount goes up. For this compound, nobody has measured that in people. So we leave it empty. We will not borrow an animal chart and pretend it works the same in people.
Fig. 5 · what the molecule is
- Kind of compound
- Peptide
- Molecule weight
- ~1,600 Da
- Half-life
- Stated in words, not a numbersee the exact wording below
- Chain length
- None on file
No amino acid sequence is on file for FGL, so none is drawn rather than guessed from a name.
The studies we cite
- Animal study2004A synthetic neural cell adhesion molecule mimetic peptide promotes synaptogenesis, enhances presynaptic function, and facilitates memory consolidation
In rats. FGL given after training gave long-lasting memory gains and helped new nerve connections form.
FGL given after training produced long-lasting memory improvement in rats and promoted synapse formation via FGFR1.
- Animal study2005A synthetic NCAM-derived peptide, FGL, protects hippocampal neurons from ischemic insult both in vitro and in vivo
In a dish and in live animals. FGL protected nerve cells after their blood supply was cut off.
Neuroprotective after ischemic injury in cultured neurons and in vivo.
- Animal study2007A neural cell adhesion molecule-derived peptide reduces neuropathological signs and cognitive impairment induced by Abeta25-35
In rats. Shots of FGL cut amyloid-type brain damage and memory problems.
Systemic FGL reduced amyloid-related pathology and cognitive impairment in a rat model.
Where to buy FGL
6 sellers list FGL in our latest read. They are ranked by trust score, then by archive rating, then by certificate tier, then by the lowest price per milligram. Archive evidence is counted before source-backed. Each path is out of 4, and the two are not added. A higher price does not raise the score. The letter is the certificate chip. 0 of them have a published certificate that names FGL.
Some seller links may pay this site when you buy through them. A payment never changes a seller's tier or rank, and no seller has a say in any page.
| Seller | Trust score | Vial sizes | From, per mg | Certificate for FGL | Seller link |
|---|---|---|---|---|---|
| Peptide Power US | 77 StrongSource-backed 4 of 4. Archive evidence 2 of 4.A | 10 mg | $6.70 | None found for FGL | View |
| Behemoth Labz | 49 WeakSource-backed 3 of 4. Archive evidence 1 of 4.B | 30 mg | $9.93 | None found for FGL | View |
| Solution Peptides | 48 WeakSource-backed 1 of 4. Archive evidence 0 of 4.C | 12 mg | $8.25 | None found for FGL | View |
| Atomik Labz | 43 WeakSource-backed 1 of 4. Archive evidence 0 of 4.C | 12 mg | $8.25 | None found for FGL | View |
| Canlab International | 37 WeakSource-backed 1 of 4. Archive evidence 1 of 4.C | 10 mg | $12.1 | None found for FGL | View |
| Boston Molecules | 28 InsufficientSource-backed 1 of 4. Archive evidence 1 of 4.C | 10 mg | $97.2 | None found for FGL | View |
- LC Lab-confirmed: the issuing laboratory echoed this certificate back
- A Current certificate, independent laboratory named, laboratory not yet checked
- B Certificate published, but no laboratory link, older than a year, or the laboratory did not recognise the published lookup
- C No certificate could be read
Every listing and vial size for FGL · How the trust score is counted
Sellers named on the price pages are ranked by certificate tier, then price, and any affiliate income is disclosed there. Naming a seller is not a recommendation to buy or use anything.
Common questions
What is the FGL dosage?
No human dose established. No published study on this page has given this compound to people and reported a result. 3 animal studies, no human study
Is FGL FDA-approved?
Not FDA-approved; experimental
Has FGL been tested in people?
Hardly at all. The memory and brain protection findings come from animal studies, so it is experimental.