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LL-37

Cathelicidin-derived antimicrobial peptide your innate immune system already makes. Used for chronic infections and biofilm-associated issues.

Immune
Evidence: Limited
Half-life
~hours
Route
Subcutaneous
Cycle
4 weeks
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 & legality
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.

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

100-500 mcg sub-q daily for 4 weeks.

Stacks well with

Thymosin Alpha-1 for compounded immune effect
BPC-157 for gut + immune

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

Educational only. User-specific dosing is between you and a qualified provider.

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 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.