The human cathelicidin antimicrobial peptide — endogenous first-line defense that’s become an off-label tool for chronic infections, biofilm disruption, and immune protocols.
LL-37 is the only cathelicidin antimicrobial peptide in humans — a 37 amino acid peptide (hence the name) produced by skin, respiratory, and immune cells as part of innate immune defense. It kills a wide range of bacteria, viruses, and fungi by disrupting their membranes, and also modulates the host inflammatory response.
LL-37 is endogenous and levels decline with age, chronic infection, or vitamin D deficiency (vitamin D directly upregulates cathelicidin production). Synthetic LL-37 is used off-label in chronic infection protocols (Lyme, chronic sinusitis, biofilm-related conditions) and immune-support contexts.
Not FDA approved. Not WADA prohibited. Research chemical with moderate scientific interest for antimicrobial and immunomodulatory applications.
LL-37’s amphipathic helical structure inserts into microbial membranes (which have different lipid composition than host cells) and disrupts them. Broad-spectrum against gram-positive, gram-negative, fungi, and some enveloped viruses.
Shown to inhibit and disrupt biofilms of Pseudomonas, Staphylococcus, and others. Biofilms are why some chronic infections are so hard to treat with conventional antibiotics; LL-37 is one of the few tools that works against them.
At sub-lethal concentrations, LL-37 modulates immune cell behavior — chemotaxis, dendritic cell differentiation, cytokine release. Dual action (direct antimicrobial + immune tuning) is why it outperforms pure antibiotics in some contexts.
Vitamin D is a direct upregulator of endogenous LL-37 production. Adequate vitamin D status supports cathelicidin synthesis; LL-37 supplementation can be viewed as working on the same axis.
| Benefit | Evidence |
|---|---|
| Broad antimicrobial | In-vitro activity against extensive pathogen list; in-vivo results less uniform |
| Biofilm disruption | Consistent preclinical; used in chronic sinusitis and biofilm-related Lyme protocols |
| Wound healing | Accelerates closure and reduces infection in chronic wounds |
| Immune modulation | Reduces LPS-driven inflammation while preserving pathogen clearance |
| Chronic Lyme adjunct | Anecdotal; used alongside Thymosin Alpha-1 and LDN in complex chronic infection protocols |
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Start Tracking FreeIn chronic infection / biotoxin illness protocols, LL-37 is often combined with Thymosin Alpha-1 (immune restoration), VIP (after Shoemaker Step 11), and Low Dose Naltrexone. Adequate vitamin D (target 40–60 ng/mL) supports the protocol since it drives endogenous cathelicidin.
LL-37 can trigger strong Herxheimer-like reactions in biofilm-loaded patients. Start at 100 mcg / 3×/week for the first 2 weeks, titrate up as tolerated.
5 mg vial + 2 mL BAC water = 2500 mcg/mL
| Dose | Volume | Syringe Units |
|---|---|---|
| 100 mcg | 0.04 mL | 4 units |
| 250 mcg | 0.10 mL | 10 units |
| 500 mcg | 0.20 mL | 20 units |
Pre-filled with a typical LL-37 (Cathelicidin) setup. Edit any field — the draw updates live.
Insulin syringe — 100 units = 1 mL
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LL-37 is not only antimicrobial — published work (PMIDs 35387840, 40869425) documents cytotoxicity to host endothelial cells (particularly under dysfunctional autophagy) and links LL-37 to endothelial dysfunction, atherogenic signaling, and impaired autophagy at higher concentrations. In psoriasis it acts as a TLR7/TLR9 autoantigen that drives plasmacytoid dendritic cell activation (PMIDs 32582207, 40869425) — a mechanism that may extend to other TLR-driven autoimmune dermatological conditions, not just psoriasis. PMID 40869425 also identifies low proteolytic stability as a known clinical limitation, which affects how predictably in-vivo peptide activity tracks the injected dose. Use caution if you have cardiovascular disease, atherosclerosis, or known endothelial dysfunction, and avoid higher-end doses without a clear reason to escalate.
LL-37 (Cathelicidin) is a research peptide not approved by the FDA for human use. It is sold only as a research chemical, and StackTrax does not endorse or facilitate personal use.
Quality varies enormously among research-chemical suppliers. At minimum, look for:
StackTrax’s preferred partner NextGen Peptides does not currently carry LL-37 (Cathelicidin)in their catalog, which is why you don’t see a direct purchase link here. Other major research-chemical suppliers carry it; we don’t specifically recommend one for this compound.
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeNo. LL-37 is not approved by the FDA for any indication and is sold in the US only as a research chemical. It is not on the WADA Prohibited List, but it has not been validated in any large human safety trial.
Yes — LL-37 is the only cathelicidin antimicrobial peptide in humans. It is a 37-amino-acid peptide (hence the name) produced by skin, respiratory, and immune cells as part of innate immune defense. Endogenous LL-37 levels decline with age, chronic infection, or vitamin D deficiency, and vitamin D directly upregulates cathelicidin production.
Community protocols commonly use 100 to 500 mcg once daily subcutaneously (abdomen), typically run as a 4 to 8 week cycle followed by 2 to 4 weeks off. Because of strong Herxheimer-like reactions in biofilm-loaded patients, the standard recommendation is to start low — 100 mcg three times per week for the first two weeks, then titrate up as tolerated.
LL-37 is amphipathic and inserts into microbial membranes (which differ in lipid composition from host cells), disrupting them across gram-positive, gram-negative, fungal, and some enveloped-virus targets. It also disrupts biofilms of Pseudomonas, Staphylococcus, and others — one reason it gets used in chronic infection protocols. At sub-lethal concentrations it modulates immune cell behavior (chemotaxis, dendritic cell differentiation, cytokine release).
Common side effects include injection-site reactions, flushing, and mild flu-like symptoms early in therapy. In chronic infection contexts, Herxheimer-like reactions (fatigue, brain fog, muscle aches from pathogen die-off) are common in the first 2 to 4 weeks. Underappreciated risks: published work documents host-endothelial cytotoxicity, links to endothelial dysfunction and atherogenic signaling at higher concentrations, and a TLR7/TLR9 autoantigen role in psoriasis. Low proteolytic stability also makes in-vivo activity less predictable than the injected dose suggests.
Avoid LL-37 in pregnancy or breastfeeding, active severe autoimmune flare, active severe psoriasis (LL-37 acts as a TLR7/TLR9 autoantigen in psoriatic skin), and active sepsis (use medical IV antibiotics instead). Use caution with cardiovascular disease, atherosclerosis, or known endothelial dysfunction, given the host-cytotoxicity signal at higher doses.
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StackTrax guides cover peptides and compounds that are not FDA-approved for the uses discussed. The dosing, reconstitution, and safety information is compiled from published research and community protocols for educational purposes only.
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