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 |
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeNot medical advice. These figures describe what is reported in the literature and what practitioners and communities do — not a recommendation, and for most compounds here no human dose-finding study exists. Talk to a qualified healthcare provider.
This page previously gave 100–500 mcg/day. The ceiling is now 200 mcg, because the only human dose-ranging data that exists runs the wrong way. In a randomised, double-blind, placebo-controlled trial in hard-to-heal venous leg ulcers (Grönberg 2014, PMID 25041740), 34 patients received topical LL-37 at 0.5, 1.6 or 3.2 mg/mL twice weekly:
The benefit does not plateau at the top dose, it disappears. One correction worth making to how this trial gets retold: the investigators reported no safety concerns for local or systemic adverse events at any dose, including 3.2 mg/mL. Claims that the top dose caused ulcer necrosis are not in the published trial. The argument against high doses here is that they stop working, not that they were shown to cause harm.
The second thing to hold onto: every human trial of LL-37 is topical. The venous leg ulcer work above, its multicentre follow-up (PMID 34687253) and the diabetic foot ulcer cream trial (PMID 37480520) are all applied to a wound bed. There is no published human pharmacokinetic or efficacy data for injected LL-37 at any dose. The subcutaneous protocols in circulation, this page’s included, are extrapolation — and LL-37 is reported to be partially inactivated by serum proteins, which is a specific reason systemic delivery may not behave like local application.
In 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.
Rosacea is a specific reason for caution, not a general one. Cathelicidin is not merely elevated in rosacea, it appears to drive it: people with rosacea express abnormally high cathelicidin in facial skin in abnormally processed forms, and injecting those peptides into mouse skin reproduces the inflammation, while deleting the cathelicidin gene abolishes it (Yamasaki 2007, Nature Medicine, PMID 17676051). Anyone with rosacea, or with the psoriasis mechanism described above, is adding a peptide their skin already over-produces. LL-37 can also trigger strong Herxheimer-like reactions in biofilm-loaded patients. Start at 100 mcg / 3×/week for the first 2 weeks, titrate up as tolerated.
Not medical advice. These figures describe what is reported in the literature and what practitioners and communities do — not a recommendation, and for most compounds here no human dose-finding study exists. Talk to a qualified healthcare provider.
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:
Lyvn does not carry LL-37 (Cathelicidin). They are the vendor we recommend elsewhere on this site, and they publish the full independent panel per batch — which makes their catalogue a useful yardstick for the criteria above even on a compound they do not stock. We are not recommending a specific supplier for LL-37 (Cathelicidin) itself, because we have no basis to.
For research use only. Not for human consumption. 21+.
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.
Disclaimer: This guide is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. The compounds discussed are not FDA approved for human use. Always consult a qualified healthcare provider before starting any new supplement or peptide protocol. StackTrax does not sell peptides or supplements directly — purchase links go to third-party vendors. StackTrax is not responsible for the products, quality, or business practices of any third-party vendor.
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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.
Before using any compound mentioned here, consult a qualified healthcare provider. StackTrax does not sell, prescribe, or recommend these substances for personal use.