Peptides
LL-37 (Cathelicidin)
Also called hCAP-18 · Cathelicidin
LL-37 attracts people looking for help with recurring infections, gut symptoms and slow healing. It is part of the body’s natural defenses, but that does not make an injected vial a proven antibiotic or an immune-system reset. The clearest human treatment research applied LL-37 directly to leg ulcers, with mixed results.
Dosage & duration
A named clinic’s reported injection example
Extension Health patient sheet
Reported use · unapproved regimen- Dose
- 200 mcg (0.2 mg) per injection
- How often
- 5 subcutaneous injections weekly
- How long
- 1 month on; break instructions conflict
The sheet alternates between 3 and 5 months off, so it cannot establish a coherent repeat-cycle plan. Its broader disease-treatment claims are not adopted.
Sources: 2
This is not the formulation or dosing used in the leg-ulcer trial. Syringe-unit figures from a clinic’s prepared solution do not transfer to another vial concentration.
Why people look into LL-37
Infections, gut symptoms and slow healing
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Recurring infections
The hope is better recovery, but injected LL-37 is not an established infection treatment.
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Gut discomfort
Bloating and other gut symptoms do not show that someone needs more LL-37.
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Slow-healing wounds
The larger topical leg-ulcer trial found no significant overall healing advantage.
Why is it discussed for infections and gut health?
LL-37 belongs to the body’s defense system, which explains interest in antimicrobial and immune effects. Websites extend that idea to chronic infection, gut symptoms and autoimmune problems. A plausible mechanism does not tell us whether an injection helps a specific person or which diagnosis they have.
What did wound research show?
The larger study tested topical LL-37 alongside compression for hard-to-heal venous leg ulcers. It did not show a significant overall healing benefit. That result should stay visible beside more enthusiastic claims based on the smaller early study. Neither study tested the clinic injection schedule shown above.
Why do online schedules disagree?
There is no validated injected immune-support course behind the various guides. Even the clinic sheet quoted here conflicts with itself about breaks. We keep the named amount visible while identifying that gap instead of combining fragments into a new protocol.
When is a different next step more useful?
A persistent wound, fever or suspected infection needs a diagnosis and appropriate treatment. Worsening symptoms after a peptide should not automatically be called “die-off” or evidence that it is working. Record the exact product and timing when seeking care.
Model details: LL-37 (Cathelicidin) · relative timing
Compare timing and buildup for this compound. The values are not blood concentrations or a measure of strength.
Shows a relative timing scenario; absolute blood concentrations are not calibrated.
Timing assumptions and sources
Legacy 0.96 h is a scenario assumption; wound-healing duration and endogenous cathelicidin concentration are not plasma elimination.
One 1 mg input peaks at 1 relative unit after a single dose. Other amounts scale proportionally; overlapping doses add when accumulation is on. Different compounds use separate relative scales.
- Timing half-life used
- 0.96 hours
- Absorption half-life assumed
- 0.24 hours
- Reference amount for the relative scale
- 1 mg
- Absorption half-life is assumed to be one quarter of the slower timescale (0.24 h); it is not a measured absorption parameter.
- A single 1-unit input has a peak of 1 relative unit; scaling and repeated-dose addition are mathematical assumptions. This normalization is independent of the example dose.
- Topical/local concentration cannot be scaled to a generic SC blood curve.
- LL-37 analog and carrier/nanoparticle PK does not establish native peptide exposure.
- Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial.
Legacy 0.96 h is a scenario assumption; wound-healing duration and endogenous cathelicidin concentration are not plasma elimination.
ll-37-relative-timing-2026-10 · version 1
Common questions
Is LL-37 a natural antibiotic?
It has antimicrobial roles in the body, but an injected LL-37 product is not an established replacement for an antibiotic selected for a diagnosed infection.
Can I use the wound-study dose as an injection dose?
No. A topical concentration applied to an ulcer is not a whole-body injection amount.
Sources Labels, studies and notes behind this guide
Catalog evidence: Human clinical trials. This describes the type of evidence, not a clinical review of every claim.
Summary and fact source checks: 2026-10-07. This records source checking, not medical review of the whole page.
Notes on the quick facts
- Why people look
- Marketing covers many conditions; none is established by the wound study.
- Human treatment data
- Topical ulcer research is separate from whole-body injection use.
- More is not better
- A bigger amount should not be assumed to improve an immune response.
- 1. HEAL LL-37 trial
148 patients; topical formulation plus compression; no significant full-population healing advantage.
- 2. Extension Health LL-37 patient sheet
Clinic’s own reported SC schedule inspected. 0.2 mg five times weekly, one-month course. Conflicting 3- versus 5-month break instructions and unrelated DSIP sentence; efficacy claims not adopted.
- 3. Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial.
Legacy 0.96 h is a scenario assumption; wound-healing duration and endogenous cathelicidin concentration are not plasma elimination.
- 4. LL-37 initial venous-ulcer trial
34 participants; topical application, early healing signals, no benefit at the highest tested concentration.
- 5. LL-37 stability in wound fluid
Original laboratory study of peptide stability/proteinases using wound fluid; not a systemic injection PK study.
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