LL-37
Cathelicidin / Human Cathelicidin Antimicrobial Peptide
LL-37 is the only human cathelicidin, an antimicrobial peptide of the innate immune system that kills microbes and disrupts biofilms in lab studies. Topical LL-37 helped venous leg ulcers in a small 2014 trial but failed its larger Phase 2b trial (2021). Injected LL-37 is untested in humans and not FDA-approved.
Half-life
Not established in humans
Typical Dose
50–100 mcg/day
60/100Route
subcutaneous
Category
immune
Evidence Overview
Strength of evidence across clinical, expert, and experimental lanes.
How LL-37 is dosed in practice
Usually taken by subcutaneous (SubQ) injection. Typical range: 50–100 mcg/day. Half-life: Not established in humans. 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.
Extensive laboratory research on LL-37 as an endogenous antimicrobial with activity against gram-positive and gram-negative bacteria, enveloped viruses and fungi; it blocks biofilm formation in lab studies and modulates inflammation. Human trials have only tested topical LL-37 on venous leg ulcers: a 34-patient randomized trial (2014) reported faster healing at the two lower doses, but the 148-patient Phase 2b trial (2021) found no significant benefit over placebo. Injected (SubQ) LL-37 has not been studied in humans.
- Reviews of LL-37 biology (2006, 2012)
- Laboratory biofilm study (2008)
- Randomized placebo-controlled trials, topical, venous leg ulcers (2014, 2021)
Used by integrative practitioners for chronic infections, Lyme disease support, and biofilm disruption. Subcutaneous injection at infection-proximal sites preferred. Often combined with BPC-157 for healing + antimicrobial coverage.
- Integrative medicine infection protocols
- Practitioner protocols
- Biofilm disruption practitioner strategies
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Known interactions with other compounds. Click nodes to explore connections.
Safety & Contraindications
- Autoimmune conditions (psoriasis, rosacea — LL-37 overexpression implicated)
- Pregnancy or breastfeeding
- Known hypersensitivity
LL-37: common questions
What is LL-37?
LL-37 is the only human cathelicidin, an antimicrobial peptide of the innate immune system that kills microbes and disrupts biofilms in lab studies. Topical LL-37 helped venous leg ulcers in a small 2014 trial but failed its larger Phase 2b trial (2021). Injected LL-37 is untested in humans and not FDA-approved.
How is LL-37 dosed?
LL-37 is usually taken by subcutaneous (SubQ) injection. Typical range in DoseCraft's library: 50–100 mcg/day. Clinical (human trials), on the skin: 0.5–3.2 mg/mL solution applied to the ulcer (about 12.5–40 mcg per cm² at the two lower strengths); Twice weekly; 4 weeks (2014 trial); 13 weeks (2021 trial). Expert (practitioner protocols): 50–100 mcg daily; Once daily; Up to 4 weeks per course. These ranges describe what has been studied or used; they are not a prescription.
Is LL-37 FDA-approved?
No. LL-37 is not approved by the FDA for any use in people.
What is the half-life of LL-37?
DoseCraft's library lists a half-life of Not established in humans. Half-life sets how often a compound is dosed and how long it takes to clear: about five half-lives.
Who should not use LL-37?
Listed contraindications: Autoimmune conditions (psoriasis, rosacea — LL-37 overexpression implicated); Pregnancy or breastfeeding; Known hypersensitivity.
Free Guides for LL-37
Information is for educational purposes only. Always consult a licensed healthcare provider before starting any peptide regimen.
Page updated . How we grade evidence: methodology.