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№ 036

LL-37

A germ-fighter your immune system already makes on its own. It's a cathelicidin-derived antimicrobial peptide used for chronic infections and biofilm-associated issues.

Immune
Evidence: Limited

LL-37: A germ-fighter your immune system already makes on its own. It's a cathelicidin-derived antimicrobial peptide used for chronic infections and biofilm-associated issues. LL-37 is an antimicrobial peptide your innate immune system already makes.

FDA ⓘ
Not approved
WADA
Not banned
Typical dose
100-500 mcg sub-q daily for 4 weeks.
Half-life ⓘ
~minutes systemically (longer locally)
Route ⓘ
Subcutaneous
Schedule
Daily
In plain English

LL-37 is an antimicrobial peptide your innate immune system already makes. People use it for chronic infections, biofilms (bacterial slime that resists antibiotics), and immune support. Strong effect in lab data, less data in humans.

Status & legalityWhat do these mean? →
Natty? ⓘ
Grey area

Naturally occurring antimicrobial peptide. Federations don't generally cover it.

FDA ⓘ
Not approved

Not FDA approved.

Compounding ⓘ
Not classified

Not formally categorized in the FDA bulks lists.

WADA ⓘ
Not listed
Prescribed ⓘ

Not prescribed in conventional medicine.

Who it's for

  • →Users with chronic biofilm-associated infections
  • →Wound-healing contexts
  • →Stack add-on for aggressive immune protocols

What to expect

  1. Week 1

    Subtle. Mild flu-like symptoms in first few doses for some users.

  2. Week 4

    Full cycle. Reassess infection markers.

  3. Week 8

    Off-cycle.

Looking at LL-37? Your next 3 steps

  1. 1Work out your exact dose

    Vial size + BAC water turns into the exact units to draw for LL-37.

    Open calculator →
  2. 2See what to stack & monitor

    The companion supplements and the bloodwork worth tracking on this kind of protocol.

    Bloodwork guide →
  3. 3Save it & ask the Coach

    A free account saves your stack; membership adds the stack-aware AI Coach.

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How it works (mechanism)

Cathelicidin-derived antimicrobial peptide (the human cathelicidin family's only member). Disrupts bacterial membranes through pore formation and modulates innate immune signaling.

Dosing protocol

Members only

Stacks well with

Members only

Side effects

01Mild flu-like symptoms early
02Injection-site irritation
03Mast-cell activation in sensitive users

When NOT to use

  • ⚠Mast cell activation syndrome (MCAS)
  • ⚠Pregnancy / nursing

Bloodwork to monitor

  • • CBC if running long courses

Common mistakes

  • • Treating it as a substitute for antibiotics (it's adjunct, not replacement)
  • • Pushing dose in MCAS-prone users
  • • Skipping the cycle break

Drug & supplement interactions

  • ⚠Mast cell activation syndrome (MCAS): may worsen, avoid
  • ⚠Limited documented interactions
Free, no account needed

New to LL-37? Grab the starter checklist.

Drop your email and we'll send the one-page first-cycle starter checklist, plus a heads-up if LL-37 changes legal status. No account needed.

No spam. No selling your email. Just the checklist and the occasional reclassification alert.

AI Coach, live sample
Members only
is 250mcg of bpc enough for a knee injury?
For a knee, 250 mcg sub-q daily is the standard working dose and a solid place to start. The trick with BPC is consistency, give it weeks, not days. Inject close to the joint, run it 4-6 weeks, and don't drop below 200 mcg, it tends to stop cracking the threshold reliably down there. If it hasn't moved at all by week 3, that's when adding TB-500 earns its place.
how much bac water for a 10mg reta vial?
3 mL is the standard play for a 10 mg reta vial. That's 3,333 mcg/mL, clean unit math across the titration: 2 mg = 60 units, 4 mg = 120 units, 6 mg = 180 units on a 100-unit insulin syringe. Run 2 mL instead if you want fewer, more concentrated shots (5,000 mcg/mL, so 2 mg = 40 units). Since most people titrate up over ~12 weeks, 3 mL 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.

Ask the Coach anything about LL-37 or your own stack. This is it working.

Trained only on Pepdex content. Does the dose math, flags interactions, knows your stack. Won't push vendors, won't pretend to be a doctor.

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Frequently asked

What is LL-37?+
LL-37 is an antimicrobial peptide your innate immune system already makes. People use it for chronic infections, biofilms (bacterial slime that resists antibiotics), and immune support. Strong effect in lab data, less data in humans.
Is LL-37 FDA approved?+
Not FDA approved.
Is LL-37 legal?+
LL-37 is not FDA-approved. It is sold by compounding pharmacies (with a prescription) and as "research only" by peptide vendors. Possession is generally not criminalized but distribution without authorization may be. Verify local laws.
Is LL-37 banned by WADA?+
LL-37 is not currently on the WADA prohibited list.
Are you still natty after taking LL-37?+
Grey area. Naturally occurring antimicrobial peptide. Federations don't generally cover it.
Do doctors prescribe LL-37?+
Not prescribed in conventional medicine.
What's the typical dose of LL-37?+
100-500 mcg sub-q daily for 4 weeks.
What are the side effects of LL-37?+
Common side effects include: Mild flu-like symptoms early; Injection-site irritation; Mast-cell activation in sensitive users. Less common effects and full safety details are on the entry page.
How long until LL-37 starts working?+
Subtle. Mild flu-like symptoms in first few doses for some users.
What can you stack with LL-37?+
Common pairings: Thymosin Alpha-1 for compounded immune effect; BPC-157 for gut + immune. Full stacking protocol and timing on the entry page.
Where do people get LL-37?+
LL-37 is most commonly sold by research-only peptide vendors and by compounding pharmacies (the latter requires a prescription). Pepdex is not a vendor, see /coa for how to verify a Certificate of Analysis before buying from any source, and /guides/scam-vendor-spotting for vendor red flags.
LL-37 vs Thymosin Alpha-1 (Tα1), which is better?+
Thymosin Alpha-1 vs LL-37: immune modulator vs direct antimicrobial peptide. Different jobs in the same system. Full head-to-head comparison: https://pepdex.co/compare/thymosin-alpha-1-vs-ll-37

Head-to-head with LL-37

Compare
LL-37 vs Thymosin Alpha-1 (Tα1) →

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