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№ 050

FGL

Studied for memory and learning in animal models. It's an FG-loop peptide modeled on the FG-loop region of NCAM (neural cell adhesion molecule).

Nootropic
Evidence: Anecdotal

FGL: Studied for memory and learning in animal models. It's an FG-loop peptide modeled on the FG-loop region of NCAM (neural cell adhesion molecule). FGL is a synthetic peptide built around a loop of NCAM, a neural cell adhesion molecule.

FDA ⓘ
Not approved
WADA
Not banned
Typical dose
No standardized human dose
Half-life ⓘ
Short (~hours)
Route ⓘ
Subcutaneous or intranasal
Schedule
Daily
In plain English

FGL is a synthetic peptide built around a loop of NCAM, a neural cell adhesion molecule. Animal-model studies show memory and learning improvements. Almost no human data. Treat it as experimental.

Status & legalityWhat do these mean? →
Natty? ⓘ
Not natty
FDA ⓘ
Not approved

Not FDA approved. Pre-clinical.

Compounding ⓘ
Not classified

Not formally categorized in the FDA bulks lists.

WADA ⓘ
Not listed
Prescribed ⓘ

Not prescribed in conventional medicine.

Who it's for

  • →Researchers studying NCAM-FGFR pathways
  • →Neuroplasticity research
  • →Educational reference, limited human data

What to expect

  1. Week 1

    Subtle. Animal models show memory-task improvements emerging.

  2. Week 4

    Cycle endpoint in most animal protocols.

  3. Week 8

    Off-cycle. No human long term data.

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How it works (mechanism)

Synthetic peptide modeled on the FG-loop of NCAM (neural cell adhesion molecule). Binds FGFR1, activating cascades that support synapse formation and memory in animal models.

Dosing protocol

Members only

Stacks well with

Members only

Side effects

01Limited human data
02Generally well tolerated in animal models

When NOT to use

  • ⚠Pregnancy / nursing
  • ⚠Anyone risk-averse to pre-clinical compounds

Common mistakes

  • • Treating it as a defined nootropic with established protocols
  • • Long cycles without safety data

What it actually is

FGL is a synthetic peptide modelled on part of NCAM, the neural cell adhesion molecule — specifically the loop that lets NCAM activate the FGF receptor. It is mainly a research tool for studying synaptic plasticity and memory. It is not entirely untested in people: a phase 1 study gave single intranasal doses of 25, 100 and 200 mg to 24 healthy men and reported pharmacokinetics and short-term tolerability. What does not exist is a therapeutic regimen or any human efficacy evidence.

NCAM sits on neuronal surfaces and helps cells find and bind each other, which matters for forming and stabilising synapses. Part of its action comes from activating the FGF receptor, and FGL is the fragment that does that. In animal models it promotes neurite outgrowth, alters synapse structure and improves memory tasks. A 2019 paper describes a conjugate designed specifically for nose-to-brain delivery, which tells you that reaching the brain is the recognised obstacle rather than an assumption.

Forms, and which is which

Research useLaboratory work

A phase 1 intranasal study established single-dose pharmacokinetics and short-term tolerability in healthy men. No therapeutic regimen followed from it.

Verdict: Phase 1 exposure data, and no established dose for any purpose.

IntranasalAttempting brain delivery

The route a 2019 delivery study specifically engineered a conjugate for, precisely because getting the peptide to the brain is hard.

Verdict: The route the delivery research targets.

Subcutaneous injectionHow community use happens

In rats, subcutaneous FGL was detected in cerebrospinal fluid and produced hippocampal FGF receptor phosphorylation, so injection is not simply futile. Human brain exposure by this route is unestablished, and the phase 1 study used the nose.

Verdict: Animal evidence for brain exposure; no human data by this route.

Established cognitive interventionsActually protecting cognition

Exercise, sleep and cardiovascular risk management have real evidence.

Verdict: The comparison worth making.

What it is claimed to do, graded

Promotes neurite outgrowth via FGF receptor activationLimited

Well demonstrated in cell work, including the 2004 paper that characterised it. This is a genuine and reproducible laboratory finding.

Alters synapse structure and improves memory in animalsLimited

Shown in a 2008 study. Animal evidence.

Improves memory or cognition in humansNone shown

One human-trial record indexed across the whole literature, and nothing establishing a cognitive outcome.

Reaches the brain when injected, in humansNone shown

In rats, subcutaneous dosing did reach cerebrospinal fluid and activate hippocampal FGF receptors. Nothing establishes the same in a person, and the human study used intranasal delivery.

Is safeLimited

A phase 1 study reported short-term tolerability of single intranasal doses in 24 healthy men. That is real human safety data, at one dose, over a short window, and it says nothing about repeated use.

Grades describe how much human evidence exists for that specific claim, not whether it will work for you or whether it is safe.

Pros and cons

Pros
  • • Genuine, reproducible laboratory science on a well-characterised receptor mechanism
  • • Well tolerated in animal models
  • • The delivery research is honest about the barrier rather than assuming it away
Cons
  • • Human exposure is limited to a single-dose phase 1 study; there is no efficacy trial
  • • No therapeutic dosing regimen exists, so any protocol offered was extrapolated
  • • Brain delivery is an acknowledged unsolved problem for this peptide
  • • Growth-factor receptor activation carries an untested tumour concern
  • • Research-chemical supply with unverified identity

When to stop

  • • Any new lump or unexplained weight loss
  • • Headache or mood change that persists
  • • Injection-site reaction that spreads
  • • Two to four weeks, on any protocol — nothing supports longer

Interactions

Active or suspected cancerAvoid

FGF receptor signalling is implicated in tumour growth and angiogenesis. Unstudied and not a formality.

Other growth-factor compoundsCaution

Compounds growth signalling with no established benefit.

Psychiatric medicationMonitor

No interaction data for a compound acting on synaptic plasticity.

Other nootropic peptidesCaution

Stacking untested compounds makes any effect unattributable.

Nothing well characterisedCaution

There is no human interaction literature for this compound.

Is this for you?

Probably worth reading further if
  • • Laboratory research. Human exposure stops at a single-dose phase 1 study with no efficacy endpoint
Skip it if
  • • You have active cancer or a personal cancer history
  • • You are pregnant or nursing
  • • You want any human evidence
  • • You are extrapolating from rat brain-exposure data to a human dose — the phase 1 study used the nose, not a needle

The one number

One phase 1 study, 24 healthy men, single intranasal doses — pharmacokinetics and tolerability only, no efficacy
Clin Pharmacokinet, 2007 (PMID 17375985)

Sources for the claims above

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AI Coach, live sample
Member answer
is 250mcg of bpc enough for a knee injury?
For a knee, is the standard working dose and a solid place to start. The trick with BPC is consistency, give it weeks, not days. , run it , and don't drop below , results tend to fall off under that line. If nothing's moved by week 3, that's when earns its place.
how much bac water for a 10mg reta vial?
is the standard play for a 10 mg reta vial. That gives you , clean unit math across the whole titration: on a 100-unit insulin syringe. Run instead if you want fewer, more concentrated shots. Most people titrate up over , and that mix keeps the numbers cleanest.
what should i track on bloodwork for tirzepatide?
Lipid panel, ALT/AST (liver enzymes), and an A1C, baseline before you start then every 3 months. If you've got metabolic-syndrome history, add fasting glucose and insulin so you can actually watch insulin sensitivity improve. You don't need a big hormone panel for a GLP-1.

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Frequently asked

What is FGL?+
FGL is a synthetic peptide built around a loop of NCAM, a neural cell adhesion molecule. Animal-model studies show memory and learning improvements. Almost no human data. Treat it as experimental.
Is FGL FDA approved?+
Not FDA approved. Pre-clinical.
Is FGL legal?+
FGL is not FDA-approved, so there is no approved prescription version. Most supply is sold as "research only" by peptide vendors. A compounding pharmacy may only use substances the FDA permits for compounding, and many research peptides are not permitted — do not assume a compounded prescription is available. Possession is generally not criminalized but distribution without authorization may be. Verify local laws.
Is FGL banned by WADA?+
FGL is not currently on the WADA prohibited list.
Are you still natty after taking FGL?+
No. FGL is a performance-enhancing peptide and would disqualify a strict natty claim.
Do doctors prescribe FGL?+
Not prescribed in conventional medicine.
What's the typical dose of FGL?+
Dosing depends on your goal, experience, and tolerance. The full FGL protocol (dose, frequency, and how to titrate) is in the members section on the entry page.
What are the side effects of FGL?+
Common side effects include: Limited human data; Generally well tolerated in animal models. Less common effects and full safety details are on the entry page.
How long until FGL starts working?+
Subtle. Animal models show memory-task improvements emerging.
What can you stack with FGL?+
FGL is commonly combined with complementary compounds. The full stacking protocol (what to pair, dosing, and timing) is in the members section on the entry page.
Where do people get FGL?+
Pepdex does not sell, ship, or recommend suppliers. FGL is not FDA-approved; prescription versions require licensed clinical care, and "research only" markets carry real legal and quality risks. /coa explains how to verify a Certificate of Analysis and /guides/scam-vendor-spotting covers the red flags.

Common questions about FGL

Tracked alongside FGL

Same goal, different aisle — each graded on its own evidence in the Pepdex catalog.

Semax →
the injectable-nootropic neighbour in the same threads
Noopept →
the oral comparison people reach for first
Choline →
the stack partner half these protocols assume
L-tyrosine →
the depleted precursor behind most focus complaints

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