LL-37
Also known as: Cathelicidin, CAP-18, hCAP18, Human Cathelicidin, CAMP
Lower numbers = closer to natural. Higher numbers = more enhanced.
Why this rating?
LL-37 is an endogenous antimicrobial peptide produced naturally by the body. Per Vandamme et al. (2012), it provides broad-spectrum antimicrobial activity and promotes wound healing via EGFR transactivation. It does NOT build muscle, burn fat, or enhance athletic performance. It is purely for healing and immune support. The body naturally produces this peptide. Rated 1 (basically natty) because faster wound healing/antimicrobial activity restores the body toward baseline rather than pushing the muscular/physique ceiling beyond what natural biology allows.
Overview
A 37-amino acid endogenous antimicrobial peptide (begins with two leucines - hence "LL") cleaved from hCAP18 by proteinase 3. Broad-spectrum antimicrobial against bacteria, fungi, and enveloped viruses. MIC 1-32mcg/mL. Promotes wound healing via EGFR transactivation, angiogenesis, and keratinocyte migration. Potent immunomodulator - attracts immune cells, neutralizes LPS endotoxin. Very short half-life limits systemic utility. Associated with psoriasis, rosacea, lupus when dysregulated.
Important Warnings
- •NOT FDA-approved for any indication
- •Very short half-life (~15-30 min) limits systemic utility
- •Cytotoxic to host cells above ~50mcg/mL
- •Associated with autoimmune conditions (psoriasis, rosacea, lupus) when dysregulated
- •May exacerbate existing autoimmune conditions
- •High salt concentrations (>150mM NaCl) reduce antimicrobial activity
- •No pharmaceutical-grade product available
- •Research-grade peptide purity varies (70-98%)
- •No direct performance enhancement - not anabolic
- •Expensive relative to alternatives
- •No human clinical data for athletic/recovery use
Purpose & Use Cases
Antimicrobial
Broad-spectrum activity against gram-positive, gram-negative bacteria, fungi, enveloped viruses. MIC 1-32mcg/mL. Synergistic with conventional antibiotics.
Wound Healing
Promotes keratinocyte migration, angiogenesis via VEGF, re-epithelialization (Heilborn et al. 2003). In a randomized placebo-controlled trial for hard-to-heal venous leg ulcers, topical 0.5mg/mL LL-37 produced a ~6-fold higher healing rate and 68% ulcer-area reduction vs placebo over 4 weeks (Grönberg et al. 2014); a larger Phase IIb trial did not meet its primary endpoint in the full population but showed benefit in larger, harder-to-heal ulcers (Mahlapuu et al. 2021).
Anti-Biofilm
Inhibits biofilm formation (IC50 4-16mcg/mL). Disrupts biofilm matrix. Potential for device-related infection prevention.
Immune Support
Enhances neutrophil phagocytosis, promotes dendritic cell maturation. LPS neutralization reduces septic response.
Benefits
- Endogenous peptide with well-characterized mechanisms
- Broad-spectrum antimicrobial activity
- Wound healing acceleration shown in a human RCT: ~6x higher healing rate than placebo at the optimal topical dose (Grönberg 2014)
- Anti-biofilm activity
- LPS/endotoxin neutralization
- Vitamin D directly upregulates the CAMP gene, raising endogenous LL-37 3-5x in vitro (effect size in vivo from oral supplementation is less clear)
- Synergistic with conventional antibiotics
- Completed randomized controlled trials in venous leg ulcers (Grönberg 2014; Mahlapuu 2021). Promising at lower topical doses, though the larger trial missed its primary endpoint in the full population
Good to Know
The body's own broad-spectrum antimicrobial peptide
LL-37 is the active form of human cathelicidin (cleaved from hCAP18), an endogenous host-defense peptide. Its amphipathic helix inserts into and ruptures negatively charged microbial membranes, giving broad-spectrum activity against bacteria, fungi, and enveloped viruses, plus immune roles (chemotaxis, neutralizing LPS endotoxin) and wound-healing signaling.
Vitamin D raises your own LL-37
Because the cathelicidin gene carries a vitamin D response element, active vitamin D directly increases CAMP/LL-37 expression, a 3-5x increase measured in cell-culture (keratinocyte) studies. Whether oral vitamin D supplementation reproduces that magnitude in living humans is less clear, but for most people fixing a vitamin D deficiency is still a cheaper, safer way to support this pathway than injecting the peptide.
Double-edged: it can drive autoimmunity
LL-37 is protective acutely but harmful when chronically elevated. LL-37-DNA complexes are implicated in the pathogenesis of psoriasis, rosacea, and lupus, and the peptide is cytotoxic to host cells (including hemolysis) above ~50 mcg/mL. Use short-term and local only, and avoid it entirely if you have an autoimmune or inflammatory skin condition.
Short half-life, local use, not anabolic
LL-37 is degraded by serum proteases within ~15-30 minutes, which limits systemic use and pushes it toward local/topical application at wound or infection sites. It has no muscle, fat, or hormonal effect (rating 1), and there is essentially no human clinical data for athletic/recovery use.
Dosage Guidelines
| Route | Typical Dose | Frequency | Cycle |
|---|---|---|---|
| Subcutaneous injection | 100 – 150 mcg/day | Topical or SubQ to wound/infection site. 1-2x daily. | 1 – 4 wk |
| Topical Solution (Wound Care) | 0.5-1.6 mg/mL solution | Twice weekly, applied to the cleaned wound bed | 4 – 13 wk |
| Intranasal Spray | 50 – 200 mcg/day | 1-2x daily (one spray per nostril), typically only during acute sinus/upper-respiratory symptoms | 1 – 3 wk |
Dosing depends on how it's administered. Pick your route in the calculator to score the one you use.
SubQ mcg dosing above is community-derived and unverified. There is no formal human PK or safety data for injectable LL-37; treat these figures as anecdotal, not clinical. The only human dosing that has actually been tested in RCTs is topical: 0.5-1.6mg/mL solution applied to venous leg ulcers twice weekly (Grönberg 2014; Mahlapuu 2021), the lowest concentration (0.5mg/mL) performed best, while 3.2mg/mL showed no benefit over placebo, suggesting a narrow therapeutic window. Animal systemic-administration studies have used roughly 0.5-5mg/kg IV/IP. Very short plasma half-life (~15-30 min) limits systemic utility and favors local/topical use. Cytotoxic to host cells at roughly 1-10µM (~4.5-45mcg/mL). High salt reduces antimicrobial activity.
0.5-1.6mg/mL LL-37 solution applied topically twice weekly (the only route with real human RCT data). By far the best-evidenced route for LL-37, though not the file's designated primary/default. Two placebo-controlled trials in venous leg ulcers tested 0.5, 1.6, and 3.2mg/mL LL-37 solution applied twice weekly: Grönberg et al. 2014 (n=17, 4-week randomized phase, ~6x higher healing rate and 68% ulcer-area reduction vs placebo at the low/mid doses) and Mahlapuu et al.
An emerging gray-market/community use (sold as 'LL-37 nasal spray' by research-peptide vendors) for sinusitis and upper-respiratory symptoms, rationalized by the fact that LL-37 is naturally expressed in nasal/airway epithelium - but there is NO clinical trial, animal PK, or safety data specific to this route. Community dosing claims vary by 5-10x between sources (25-50mcg per nostril vs. 100-500mcg per actuation), which strongly suggests low-quality/AI-generated marketing content rather than genuine consensus; the 50-200mcg/day figure here is a conservative synthesis, not a verified dose.
The ~15-30 minute plasma half-life reflects rapid degradation by serum proteases, which limits systemic utility and favors local/topical use.
Side Effects
Local Irritation
commonTransient erythema, burning sensation at application site.
Usually self-limiting. Apply to clean, dry skin.
Hemolysis (High Doses)
uncommonCan lyse red blood cells at concentrations >50mcg/mL.
Keep concentrations below cytotoxic threshold. Primarily local application.
Pro-inflammatory Effects
uncommonMay exacerbate autoimmune conditions. Mast cell activation at high doses.
Avoid in psoriasis, rosacea, lupus. Use lowest effective dose.
Autoimmune Associations
rareLL-37-DNA complexes linked to psoriasis, rosacea, lupus pathogenesis when chronically elevated.
Short-term, local use only. Monitor for signs of autoimmune flare.
General Mitigation Strategies
Local application minimizes systemic exposure and side effects. Very short half-life means effects clear quickly. Cytotoxic to host cells above ~50mcg/mL - stay below this concentration. Associated with autoimmune conditions when chronically elevated - use short-term for specific purposes. Vitamin D3 can naturally increase LL-37 expression 3-5x as an alternative approach.
Support Supplements
Ancillary supplements commonly run alongside LL-37 to manage side effects, support the target tissue, or fill nutrient demands it creates.
Vitamin D3
KeyThe CAMP (cathelicidin/LL-37) gene is under direct transcriptional control of a vitamin D response element. Active vitamin D (1,25-dihydroxyvitamin D) drives your own LL-37 production, shown as a 3-5x increase in cell-culture (keratinocyte) studies. Correcting a deficiency is a far lower-risk route than injecting the peptide, though oral supplementation trials have not clearly reproduced that same magnitude of effect in vivo.
- Dose
- ~1,000-5,000 IU/day, titrated to a blood 25(OH)D in range
- Timing
- Daily with a fat-containing meal
- When
- Most useful as a safer alternative or complement to exogenous LL-37; test 25(OH)D and avoid megadosing.
Post Cycle Therapy (PCT)
Does not affect HPT axis. Endogenous peptide. No PCT required.
How It Works
Amphipathic alpha-helical peptide that inserts into negatively charged bacterial membranes, creating pores and causing lysis. Electrostatic attraction to bacterial lipopolysaccharides (gram-negative) and lipoteichoic acids (gram-positive). Immunomodulation: activates FPRL1, P2X7, EGFR receptors. Chemotaxis for neutrophils, monocytes, mast cells, T cells. Binds/neutralizes LPS endotoxin. Wound healing via VEGF upregulation and EGF/FGF release.
Fundamentals
Reference on the practices relevant to LL-37: how they are done and where they go wrong. Not a recommendation to use it.
Common Stacks
- LL-37 + BPC-157 + TB-500 - comprehensive wound/injury healing
- Increase vitamin D3 intake to naturally boost LL-37 expression (3-5x)
- Apply locally to wound sites - systemic use limited by short half-life
- Consider for infection prevention in cuts/abrasions
- Short-term use only - avoid chronic elevation
Legal Status
Not FDA-approved; research chemical only. Not a controlled substance and not specifically on the WADA Prohibited List. It is a natural endogenous peptide produced by the body.
Legal status varies by country and changes over time. This is a general summary, not legal advice.
WADA Status
LL-37 is not specifically listed on the WADA Prohibited List. It is an endogenous antimicrobial peptide with no direct performance-enhancing effect, but as a non-approved research peptide it could still fall under S0 (non-approved substances) for tested athletes, so its status is genuinely unclear. Verify before competition.
References
- Vandamme D et al. - A comprehensive summary of LL-37, the factotum human cathelicidin peptide (Cell Immunol 2012)
- Kahlenberg & Kaplan - Little peptide, big effects: LL-37 in inflammation and autoimmune disease (J Immunol 2013)
- Fabisiak A et al. - LL-37: cathelicidin-related antimicrobial peptide with pleiotropic activity (Pharmacol Rep 2016)
- Heilborn JD et al. - LL-37 in re-epithelialization of human skin wounds (J Invest Dermatol 2003)
- Grönberg A et al. - Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial (Wound Repair Regen 2014)
- Mahlapuu M et al. - Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: a phase IIb multicentric randomized, placebo-controlled clinical trial (Wound Repair Regen 2021)