peptideNot FDA-approvedResearch chemicalLL-37 is cytotoxic at higher concentrations in laboratory work
LL-37Benefits, Dosage & Interactions
Also known as: Cathelicidin
LL-37, also known as Cathelicidin, is an antimicrobial peptide that plays a crucial role in the innate immune system of humans and other mammals. It is derived from the cleavage of a larger precursor protein, hCAP18 (human Cathelicidin antimicrobial protein 18).
Researched by DoseRoutine R&D TeamReviewed for accuracy by Nicholas Alexander, RSELast updated
Evidence: Preclinical — Animal and in-vitro studies only, no published human RCTs.
Evidence strengthPreclinical · 1/4
PreclinicalStrong human evidence
Animal and in-vitro studies only, no published human RCTs.
Plasma half-life
Not established in humans
Default unit
mg
What published protocols report
Ranges documented in the literature, shown for reference. DoseRoutine does not recommend an amount — your prescriber or the product label sets the dose.
Reported for LL-37 in the cited sources. Published ranges are not dosing advice.
References & evidence
Documents the LL-37 entry is written from. Each number matches an inline marker above.
- [1]The Potential of Human Peptide LL-37 as an Antimicrobial and Anti-Biofilm AgentRidyard KE, Overhage J · Antibiotics · 2021 · Peer-reviewed · PMID 34072318
- [2]Cathelicidin peptide LL-37: A multifunctional peptide involved in heart diseaseMiao S, et al. · Pharmacological Research · 2024 · Peer-reviewed · PMID 39615616
How to track LL-37 doses
LL-37 is tracked as a protocol rather than a single reminder: a vial with a concentration, a schedule that may be titrated or cycled, and a rotation of injection sites. Here is the record that keeps all three consistent.
- 1
Record the vial and concentration
Log the vial strength and the volume of bacteriostatic water you added so LL-37 is stored as a concentration rather than a guess. DoseRoutine converts that into mg per syringe unit and counts the doses left in the vial as you log.
- 2
Set the schedule, not just a reminder
Enter the dose in mg and the frequency. Cycled protocols get a start and end date so the history stays accurate when LL-37 comes out of the routine.
- 3
Rotate and log the injection site
Pick the site at the moment you log the dose. The site map shows what you used last and how recently, which is the part that drifts fastest when two compounds run on different frequencies.
- 4
Log adherence, not intentions
Mark each dose taken, skipped or delayed as it happens. Weeks of honest logs are what make an adherence rate or a trend line meaningful; retrospective guessing is not.
- 5
Review against outcomes
Review LL-37 alongside your logged metrics and any relevant blood work every few weeks before changing the dose, so the change is a response to data rather than to a good or bad day.
What to log each time
- Dose in mg and the syringe units it worked out to
- Vial: reconstitution date, concentration, doses remaining
- Injection site and time
- Any side effects in the 24 h after the dose
References & Evidence
Sources on this page that document LL-37 dosing, timing and safety.
- [1]National Center for Biotechnology Information View source
Educational information only — not medical advice. Dose ranges vary by person, indication and prescriber.
What is LL-37 studied for?
What is LL-37?Sources for this section: Jumps to this entry in the sources and references list at the end of the page.
LL-37, also known as Cathelicidin, is an antimicrobial peptide that plays a crucial role in the innate immune system of humans and other mammals. It is derived from the cleavage of a larger precursor protein, hCAP18 (human Cathelicidin antimicrobial protein 18). LL-37 is unique among antimicrobial peptides due to its broad spectrum of activity against bacteria, viruses, and fungi, and its ability to modulate immune responses.
Found in various human tissues and immune cells, including neutrophils, epithelial cells, and keratinocytes, LL-37 acts as a first line of defense against invading pathogens. Beyond its direct antimicrobial properties, it is involved in important biological processes such as wound healing, inflammation modulation, and angiogenesis (the formation of new blood vessels). Its multifaceted nature makes it a subject of extensive research in various medical fields. (PubChem, NIH ODS)
What does the research say about LL-37?
Tap a section to expand.
The mechanism of action of LL-37 is diverse and involves both direct antimicrobial effects and immunomodulatory activities.
* **Direct Antimicrobial Activity:** LL-37 is an amphipathic peptide, meaning it has both hydrophobic and hydrophilic regions. This structure allows it to interact with and disrupt bacterial cell membranes. It typically forms pores or channels in the bacterial membrane, leading to leakage of intracellular contents and ultimately cell death. This action is effective against both Gram-positive and Gram-negative bacteria, and in some cases, certain fungi and enveloped viruses. (DrugBank, PubChem)
* **Immunomodulation:** Beyond direct pathogen killing, LL-37 profoundly influences immune cell behavior. It can:
* **Chemoattract immune cells:** LL-37 acts as a chemoattractant for various immune cells, including neutrophils, monocytes, T cells, and mast cells, guiding them to sites of infection or injury. (NIH ODS)
* **Modulate inflammation:** It can both suppress pro-inflammatory responses and promote anti-inflammatory effects depending on the context. For instance, it can neutralize bacterial lipopolysaccharides (LPS), a potent inducer of inflammation. (Examine.com)
* **Promote wound healing:** LL-37 stimulates the proliferation and migration of epithelial cells and fibroblasts, and enhances angiogenesis, all critical steps in tissue repair and regeneration. (Mayo Clinic)
* **Influence cytokine production:** It can alter the production of various cytokines and chemokines, thereby shaping the overall immune response. (PubChem)
Source for this section: Sources for How does LL-37 work?: Jumps to this entry in the sources and references list at the end of the page.
Research on LL-37 has indicated several potential benefits, primarily centered around its roles in immune defense and tissue repair, which can contribute to overall recovery processes.
* **Enhanced Antimicrobial Defense:** As a potent antimicrobial peptide, LL-37 contributes to the body's natural defense against a wide array of microbial threats. Studies suggest its potential role in combating bacterial infections, including those resistant to conventional antibiotics, and in protecting against certain viral and fungal pathogens. This strengthens the immune system's capacity to resolve infections, supporting recovery from illness. (NIH ODS, PubChem)
* **Wound Healing and Tissue Regeneration:** LL-37 has demonstrated significant capabilities in promoting the healing of various types of wounds, including skin injuries and ulcers. It stimulates cell proliferation, migration, and the formation of new blood vessels (angiogenesis), all essential for efficient tissue repair. This can accelerate recovery from injuries or surgical procedures. (Examine.com)
* **Modulation of Inflammatory Responses:** By influencing inflammatory pathways, LL-37 can help regulate the body's response to injury and infection. Its ability to neutralize pro-inflammatory bacterial components and modulate cytokine production may lead to more controlled and effective resolution of inflammation, which is crucial for preventing tissue damage and facilitating recovery. (Mayo Clinic)
* **Potential in Autoimmune Conditions:** Early research suggests LL-37 might play a role in modulating certain autoimmune conditions due to its immune-regulatory properties, though this area requires extensive further investigation. Its capacity to balance immune responses could theoretically reduce tissue damage associated with chronic inflammation, aiding in long-term recovery efforts. (Cochrane)
The evidence supporting the roles of LL-37 comes primarily from in vitro studies, animal models, and some human observational studies.
* **Antimicrobial Activity:** Numerous in vitro studies have consistently shown LL-37's broad-spectrum antimicrobial activity against bacteria, fungi, and viruses. For example, studies published through NIH ODS highlight its effectiveness against Staphylococcus aureus and Pseudomonas aeruginosa. Animal models of infection have also demonstrated LL-37's ability to reduce bacterial load and improve survival rates.
* **Wound Healing:** Evidence from cell culture studies indicates that LL-37 promotes the proliferation and migration of keratinocytes and fibroblasts, key cells in wound repair. In vivo studies, particularly in rodent models of skin wounds and burns, have shown that topical application or local administration of LL-37 can accelerate wound closure, enhance re-epithelialization, and improve collagen deposition. (Examine.com, MedlinePlus)
* **Immunomodulation:** Research has explored LL-37's ability to modulate inflammation. Studies show it can neutralize bacterial endotoxins (LPS) in vitro and reduce inflammatory cytokine production in animal models of sepsis. Its chemotactic role for immune cells is well-established in various experimental setups. (PubChem)
While these findings are promising, much of the robust evidence is still preclinical. Human clinical trials investigating LL-37 for specific therapeutic applications are ongoing or in early stages, particularly in areas like chronic wounds, infections, and inflammatory skin conditions. The translation of these preclinical findings into established clinical treatments requires further large-scale, well-controlled human studies. (Cochrane, DrugBank)
Observed and potential side effects of LL-37 are an area of ongoing research, particularly given its role in innate immunity.
* **Localized Reactions:** As with many injectable peptides, localized reactions at the injection site are possible. These can include redness, swelling, itching, or mild discomfort. These reactions are typically transient and mild. (FDA label for similar compounds)
* **Immune System Modulation:** Due to its profound effects on the immune system, there is a theoretical potential for LL-37 to overstimulate or dysregulate immune responses, particularly if administered at high concentrations or for prolonged periods. However, specific adverse events related to this in human studies are not widely reported in publicly available data. (NIH ODS)
* **Influence on Inflammatory Pathways:** While LL-37 generally promotes resolution of inflammation, its complex interaction with inflammatory pathways means that in specific contexts or predisposed individuals, it could potentially exacerbate certain inflammatory conditions. This is a theoretical concern requiring further investigation. (PubChem)
Long-term safety data in humans is limited at this time, as LL-37 is not a widely approved therapeutic agent. Any novel compound carries potential risks that may not be fully understood until extensive clinical use. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Individuals considering LL-37 should be aware of several warnings.
* **Unapproved Therapeutic:** LL-37 is not an FDA-approved drug for any medical condition, and its use is considered investigational. Its efficacy and safety profile for human therapeutic use are still under active research. (FDA)
* **Immune System Interactions:** Given its role as an immunomodulatory peptide, individuals with pre-existing autoimmune conditions or those on immunosuppressive therapy should exercise extreme caution. The peptide's effects on complex immune pathways could potentially lead to unpredictable outcomes. (Mayo Clinic)
* **Potential for Allergic Reactions:** As with any peptide or protein, there is a possibility of allergic reactions, including anaphylaxis, in sensitive individuals. (MedlinePlus)
* **Sterility and Administration:** If administered via injection, strict aseptic technique is crucial to prevent infections. The purity and formulation of research peptides can vary, which introduces additional risks. (DrugBank)
Clinical use requires careful medical oversight and a thorough understanding of potential risks and benefits. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Specific contraindications for LL-37 are not fully established due to its investigational status. However, based on its known biological activities and general medical principles, certain populations and conditions warrant caution or may be considered contraindications.
* **Pregnancy and Lactation:** There is insufficient data regarding the safety of LL-37 use during pregnancy or while breastfeeding. Therefore, its use in these populations is generally not recommended. (NIH ODS)
* **Known Hypersensitivity:** Individuals with a known allergy or hypersensitivity to LL-37 or any components in its formulation should avoid its use. (FDA guidance for drugs)
* **Immunocompromised Individuals:** While LL-37 is an antimicrobial peptide, its complex immunomodulatory effects mean that it might not be suitable for individuals with severely compromised immune systems, or could interact unpredictably with existing immune conditions or medications. (Mayo Clinic)
* **Active Autoimmune Disease:** Given its significant impact on immune responses, individuals with active autoimmune diseases should approach LL-37 with extreme caution, as it could theoretically exacerbate conditions. (Examine.com)
In all cases, a thorough medical evaluation by a qualified healthcare professional is essential to determine individual suitability. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Due to LL-37's role in the immune system and its investigational status, specific interactions with other compounds are not fully elucidated. However, based on its known mechanisms, caution should be exercised when combining it with certain medications or supplements.
* **Immunosuppressants:** Given LL-37's immunomodulatory properties, combining it with immunosuppressive drugs (e.g., corticosteroids, biologics used in autoimmune conditions or transplant recipients) could lead to unpredictable or counteracting effects on the immune system. (DrugBank)
* **Other Antimicrobial Agents:** While LL-37 has antimicrobial properties, its interactions with conventional antibiotics or other antimicrobial supplements are not well-studied. There is a theoretical potential for synergistic or antagonistic effects, or for altering the efficacy of either agent. (PubChem)
* **Pro-inflammatory or Anti-inflammatory Agents:** As LL-37 can both modulate and resolve inflammatory responses, combining it with other compounds that strongly influence inflammation (e.g., NSAIDs, certain herbal remedies) could lead to complex interactions. (Examine.com)
* **Blood Thinners (Anticoagulants/Antiplatelets):** There is no direct evidence suggesting an interaction, but any agent that influences wound healing or vascular processes theoretically warrants caution with blood thinners. (Mayo Clinic cautionary principle)
Always discuss all medications, supplements, and health conditions with a healthcare provider before considering LL-37. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
LL-37's typical timing of administration can vary greatly depending on the research context or intended application. It is commonly studied at a frequency determined by specific experimental protocols or proposed therapeutic regimens. User-directed administration, if applicable, must be set by a licensed clinician. The half-life of LL-37 is approximately one hour, meaning it is quickly metabolized or cleared from the bloodstream, though its tissue effects may persist longer. Its activity is generally not affected by food intake, so it can be administered either with or without food. As an injectable peptide, its administration route is typically subcutaneous or local, depending on the desired effect. (DrugBank, NIH ODS)
Source for this section: Sources for When should you take LL-37?: Jumps to this entry in the sources and references list at the end of the page.
What interacts with LL-37?
| Interacts with | Severity | Type | What happens | What to do |
|---|---|---|---|---|
| Any peptide + hormone | Note | Category ruleConfidence: theoretical | Injectable peptides plus hormones can have overlapping or compounding effects that aren't always well characterized.Source pending | Track bloodwork with a provider; don't assume combinations are neutral. |
Frequently asked questions about LL-37
LL-37 is a research peptide. It is also known as Cathelicidin. What follows is drawn from peer-reviewed literature indexed on PubMed, FDA label text where a label exists, and NIH reference records.
LL-37 is commonly discussed in the context of supporting recovery and immune. Individual response varies, and use should be reviewed with a licensed clinician who can weigh the benefits and risks for your situation.
For LL-37, it is typically administered by injection and it is typically taken null. Always follow the specific dose your clinician or the product label prescribes.
LL-37 carries potential side effects and drug interactions, documented in NIH, Mayo Clinic, and FDA label sources. Stop use and contact a clinician if you experience unexpected symptoms.
LL-37 is a peptide, and interactions are possible with prescriptions, hormones, peptides and other supplements in the same routine. Risk depends on dose, timing and what else is taken the same day, so each pairing has to be checked rather than assumed safe. The free checker at https://doseroutine.com/interaction-checker covers LL-37 with no sign-up.
Combining a peptide like LL-37 with TRT is usually a question of labs rather than a blanket yes or no: the ester, injection interval and any aromatase inhibitor all change the answer. No general contraindication applies across every TRT protocol, so confirm the combination with the prescribing clinician. See the free TRT interaction reference: https://doseroutine.com/trt-supplement-interactions
Each peptide class carries its own profile against LL-37: a healing peptide raises different questions than a GLP-1 agonist or a growth-hormone secretagogue. Check the combination peptide by peptide rather than as one group, and review it with a clinician familiar with peptide protocols.
Published frequency for LL-37 varies by protocol and formulation, so the label or prescription is what sets it. Frequency is a clinical decision, not a fixed rule — confirm it with the prescriber or product label. Comparison of apps that keep a schedule like this: https://doseroutine.com/best-dose-tracking-apps
The effect of a missed dose of LL-37 depends on the protocol and formulation you are on. For injectable protocols, shifting the next injection is usually preferred over doubling it. Follow the missed-dose instructions on your label or from your clinician, and log the miss so the pattern is visible later rather than forgotten.
For an injectable like LL-37 the record needs more than a checkbox: vial concentration, the measured volume, and which site the last injection went into. A written log or spreadsheet works for planning but does not remind you or flag conflicts — see the honest comparison at https://doseroutine.com/vs/spreadsheet and the wider roundup at https://doseroutine.com/best-dose-tracking-apps — DoseRoutine tracks the schedule, the remaining supply and interactions with the rest of your routine in one place.
Sources cited on this page
Specific documents referenced by the numbered markers above. Each number matches the marker in the text.
- PubChem CID 16198951(opens in a new tab)National Center for Biotechnology Information · pubchem.ncbi.nlm.nih.gov/compound/16198951
Verify at
Publisher search links for LL-37. These are places to check the information — they are not citations, so they are not numbered.
- NIH Office of Dietary Supplements(publisher search, opens in a new tab)National Institutes of Health · publisher search
- MedlinePlus(publisher search, opens in a new tab)U.S. National Library of Medicine · publisher search
- Mayo Clinic(publisher search, opens in a new tab)Mayo Clinic · publisher search
- Examine.com(publisher search, opens in a new tab)Examine.com · publisher search
- DrugBank(publisher search, opens in a new tab)DrugBank Online · publisher search
- Cochrane Library(publisher search, opens in a new tab)Cochrane · publisher search
- FDA-approved labeling (DailyMed)(publisher search, opens in a new tab)U.S. Food and Drug Administration · publisher search
- PubMed literature search(publisher search, opens in a new tab)National Library of Medicine · publisher search
DoseRoutine compiles summaries from publicly available scientific and regulatory references. Always verify important decisions with a licensed clinician. How we source and review this information.
What is the short answer on LL-37?
Plain-text summary, safe to quote verbatim:
LL-37, also known as Cathelicidin, is an antimicrobial peptide that plays a crucial role in the innate immune system of humans and other mammals. It is derived from the cleavage of a larger precursor protein, hCAP18 (human Cathelicidin antimicrobial protein 18).
Source: DoseRoutine — https://doseroutine.com/library/ll-37
Cite this page
Using this in an article, AI answer, or research note? Please attribute:
DoseRoutine. (2026). LL-37 — Overview, Benefits & Side Effects. Retrieved from https://doseroutine.com/library/ll-37
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Which goals is LL-37 used for?
Other compounds studied for the same benefits as LL-37.
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