FGL (FG Loop)
FGL peptide / NCAM mimetic peptide / Fibroblast Growth Loop
A 15-amino-acid peptide derived from the second fibronectin type III module (F3II) of Neural Cell Adhesion Molecule (NCAM). FGL mimics the NCAM-FGFR interaction, activating FGFR signaling pathways that promote synaptic plasticity, long-term potentiation, and memory formation. It enhances spatial memory and has neuroprotective effects against excitotoxicity without the mitogenic risks of full FGF ligands.
Half-life
~4–6 hours
Typical Dose
1–5 mg SC 2–3x/week
3/5Route
subcutaneous
Category
neuroprotective
Evidence Overview
Strength of evidence across clinical, expert, and experimental lanes.
How FGL (FG Loop) is dosed in practice
Usually taken by subcutaneous (SubQ) injection. Typical range: 1–5 mg SC 2–3x/week. Half-life: ~4–6 hours. Each card gives the dose, frequency and duration from one evidence lane: Clinical (human trials), Expert (practitioner protocols) or Experimental (early or animal data). These ranges describe what has been studied or used; they are not a prescription.
Work out the units to draw with the reconstitution calculator, how long a vial lasts with the vial duration calculator, and how levels fall between doses with the half-life calculator.
The only published human study (2007, 24 healthy men) gave single intranasal doses up to 200 mg. They were well tolerated, with brief nasal burning at 200 mg, and plasma levels were detectable only at 100–200 mg. No efficacy trials have been published.
- Phase 1 study in healthy men (2007)
Small but enthusiastic community of users reports improved memory, learning speed, and verbal fluency. Still very niche due to limited availability and high cost. Often combined with other nootropic peptides in advanced cognitive stacks.
- Longecity forum — FGL peptide experience reports
- Nootropic community protocols for NCAM modulation
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Upgrade to ProSafety & Contraindications
- Active cancer (activates FGFR growth signaling)
- Pregnancy or breastfeeding
- Known hypersensitivity to peptide compounds
FGL (FG Loop): common questions
What is FGL (FG Loop)?
A 15-amino-acid peptide derived from the second fibronectin type III module (F3II) of Neural Cell Adhesion Molecule (NCAM). FGL mimics the NCAM-FGFR interaction, activating FGFR signaling pathways that promote synaptic plasticity, long-term potentiation, and memory formation. It enhances spatial memory and has neuroprotective effects against excitotoxicity without the mitogenic risks of full FGF ligands.
How is FGL (FG Loop) dosed?
FGL (FG Loop) is usually taken by subcutaneous (SubQ) injection. Typical range in DoseCraft's library: 1–5 mg SC 2–3x/week. Clinical (human trials), as a nasal spray: Single intranasal doses of 25, 100 or 200 mg (phase 1, healthy men); Single dose; Single dose; no repeat-dose or patient trials. Experimental (early or animal data): 1–5 mg SC 2–3x/week; 2–3 times weekly; 4–8 week cycles. These ranges describe what has been studied or used; they are not a prescription.
Is FGL (FG Loop) FDA-approved?
No. FGL (FG Loop) is not approved by the FDA for any use in people.
What is the half-life of FGL (FG Loop)?
DoseCraft's library lists a half-life of ~4–6 hours. Half-life sets how often a compound is dosed and how long it takes to clear: about five half-lives.
Who should not use FGL (FG Loop)?
Listed contraindications: Active cancer (activates FGFR growth signaling); Pregnancy or breastfeeding; Known hypersensitivity to peptide compounds.
Information is for educational purposes only. Always consult a licensed healthcare provider before starting any peptide regimen.
Page updated . How we grade evidence: methodology.