Trust Signals
- Written by: FormBlends Medical Team, reviewed against PubMed-indexed primary literature
- Evidence standard: Every dosing claim is graded by evidence type. Speculative or community-derived protocols are labeled as such.
- No financial incentive: This page does not promote a specific product. Comparisons concede where LL-37 loses.
- Anti-fabrication: No invented statistics. Where precise human data is absent, we say so and give a directional range instead.
- Last reviewed: 2026-05-29
Key Takeaways
- No FDA-approved LL-37 dose exists. The most commonly cited research range for subcutaneous injection is 100 to 300 mcg per administration, drawn from small human exploratory trials, not large RCTs.
- LL-37 is a 37-amino-acid cathelicidin peptide (molecular weight approximately 4493 Da) with a plasma half-life estimated at under 1 hour in animal models, meaning dosing frequency matters more than with longer-lived peptides.
- At concentrations required for direct antimicrobial killing in vitro (typically low micromolar), LL-37 also becomes cytotoxic to host erythrocytes. Systemic dosing high enough to replicate in vitro antimicrobial effects carries real hemolytic risk.
- A credible certificate of analysis for LL-37 5mg research vials must include HPLC purity above 95 percent, mass spectrometry confirmation, and endotoxin testing below 1 EU/mg for any injectable use.
- Community cycling protocols (4 weeks on, 2 weeks off) are convention extrapolated from other peptides, not derived from LL-37 specific clinical data.
Direct Answer: What Is the LL-37 Peptide Dosage?
LL-37 has no approved human dose. Small exploratory trials and published case series have used roughly 25 mcg to 500 mcg per subcutaneous injection, with 100 to 300 mcg being the most commonly referenced range. Frequency runs from daily to three times weekly. Evidence quality is Low to Very Low for all systemic protocols. Treat every number here as a research reference, not a prescription.
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- What is LL-37 and why does its structure matter for dosing?
- Evidence ledger: what does the research actually support?
- Route-by-route dosing tables
- How do you reconstitute an LL-37 5mg vial?
- What most pages get wrong about LL-37 dosage
- Why does LL-37 degrade and how does that affect dose accuracy?
- Honest head-to-head: LL-37 vs. approved alternatives
- COA and label literacy: how to evaluate what you are buying
- Side effects and dose-dependent toxicity
- FAQ
- Sources
What Is LL-37 and Why Does Its Structure Matter for Dosing?
LL-37 is the only known human cathelicidin, encoded by the CAMP gene and processed from the precursor protein hCAP-18. The mature peptide contains 37 amino acids, carries a net positive charge (cationic), and adopts an amphipathic alpha-helix in the presence of membranes. This helix is what drives both its antimicrobial mechanism (membrane disruption) and its dose-limiting toxicity (disruption of host cell membranes at high concentrations).
Molecular weight is approximately 4493 Da. This is large enough that intact-skin topical penetration is poor without a carrier, and it is rapidly degraded by serine proteases in serum and tissue, including kallikreins and matriptase. The consequence for dosing: a short functional half-life (estimated under 60 minutes in rodent models based on peptide detection studies), meaning that sustained local effect likely requires either frequent dosing, depot formulations, or direct tissue delivery.
Evidence Ledger: What Does the Research Actually Support?
| Claim / Use Case | Best Evidence Type | Sample Size (largest) | Effect Direction | Confidence |
|---|---|---|---|---|
| Antimicrobial activity in vitro | Cell culture, MIC studies | N/A (lab) | Positive (concentration-dependent) | High (in vitro only) |
| Wound healing acceleration, topical/intradermal | Small Phase I/II human trial (Lipigon/Bone Therapeutics chronic leg ulcer work) | Under 50 subjects | Positive trend | Low |
| Immunomodulation / anti-inflammatory cytokine shift | Animal models, some ex vivo human cell data | Animal (rodent) | Positive | Very Low (for humans) |
| Angiogenesis promotion | Cell culture, animal wound models | Animal | Positive | Very Low (for humans) |
| Subcutaneous systemic dosing safety | No published human RCT | N/A | Unknown | Very Low |
| Hemolytic toxicity at high doses | In vitro red blood cell studies, animal data | Lab / animal | Confirmed at supratherapeutic concentrations | Moderate (mechanism confirmed) |
| Oral bioavailability | Pharmacokinetic reasoning, no human trial | N/A | Expected negligible (proteolysis) | Very Low |
Route-by-Route Dosing Tables: What Research Protocols Have Used
| Route | Reported Research Range | Frequency (reported) | Evidence Basis | Confidence |
|---|---|---|---|---|
| Subcutaneous injection | 100 to 300 mcg per dose | Daily to 3x per week | Community protocols referencing small exploratory studies | Very Low |
| Intradermal (wound site) | Low mcg range per injection point; multi-point grid used in trials | Weekly in wound trials | Small Phase I/II wound trial data | Low |
| Topical gel/cream | Roughly 1 to 10 micromolar in formulation | Once to twice daily | Cell culture translation; small clinical wound studies | Very Low |
| Inhaled (nebulized) | Investigational (cystic fibrosis and lung infection models) | Not standardized | Animal and early human airway studies | Very Low |
| Oral | Not viable; destroyed by GI proteases | N/A | Pharmacokinetic inference | Moderate (for futility of this route) |
| Intravenous | Animal sepsis models only | N/A for humans | Rodent data; no human IV trials published | Very Low; safety unknown in humans |
Protocol Duration
Published research trials have run from single-dose pharmacokinetic studies up to 8 to 12 week wound-healing courses. Community-derived cycling patterns (4 weeks on, 2 weeks off) have no LL-37-specific clinical basis. They are borrowed conventions from peptide communities applying logic from other research compounds.
How Do You Reconstitute an LL-37 5mg Vial?
Reconstitution math is where dosing errors most commonly occur. Work this out before drawing any volume.
| Target Concentration | Bacteriostatic Water to Add (5mg vial) | Resulting Dose per 0.1 mL | Resulting Dose per 0.5 mL |
|---|---|---|---|
| 1 mg/mL (1000 mcg/mL) | 5 mL | 100 mcg | 500 mcg |
| 500 mcg/mL | 10 mL | 50 mcg | 250 mcg |
| 250 mcg/mL | 20 mL | 25 mcg | 125 mcg |
Practical steps: Wipe the vial septum with 70 percent isopropyl alcohol. Inject bacteriostatic water gently against the vial wall, do not aim directly at the lyophilized cake. Swirl gently, do not vortex or shake (promotes aggregation). Visually confirm the solution is clear and colorless before drawing. Any particulate matter, cloudiness, or off-color appearance is a discard signal.
Use a 1 mL insulin syringe for subcutaneous administration. At 500 mcg/mL, drawing to the 0.2 mL mark delivers 100 mcg. At 1 mg/mL, the same 0.2 mL mark delivers 200 mcg. Write the concentration on the vial label immediately after reconstitution. This single step prevents the most common dosing error in research peptide protocols.
What Most Pages Get Wrong About LL-37 Dosage
This is the section competitor pages skip entirely.
1. Conflating in vitro MIC with a systemic dose target. Many community protocol pages cite the minimum inhibitory concentration of LL-37 against Staphylococcus aureus (often in the 1 to 5 micromolar range) and imply you need to "reach" that concentration systemically. This is biologically illiterate for two reasons: (a) LL-37 is degraded within minutes to tens of minutes in serum by host proteases, and (b) the concentrations required to kill bacteria are within the same range that causes hemolysis of human red blood cells. Systemically targeting bactericidal concentrations is not just difficult, it is likely dangerous.
2. Ignoring the aggregation problem. LL-37 has a strong tendency to self-aggregate, especially at higher concentrations and in the presence of salt. Aggregated peptide is not bioactive in the same way as monomeric or small-oligomeric LL-37. If a reconstituted vial becomes turbid or shows particulate matter, the effective dose delivered may be a fraction of what you calculated, and aggregates carry their own inflammatory and injection-site risk.
3. Presenting cycling protocols as evidence-based. The 4 on, 2 off pattern circulating in forums has no published LL-37 trial behind it. It is a structural convention borrowed from peptides where receptor downregulation or axis suppression is the rationale for cycling. LL-37 does not primarily act through a receptor system where this concern clearly applies. The cycling advice is plausible but speculative.
4. Overlooking endotoxin contamination as a dose confound. Research-grade LL-37 produced by solid-phase peptide synthesis can carry lipopolysaccharide (LPS) contamination if quality control is poor. LPS is itself a potent immune stimulator. Observed "immunomodulatory" effects from poorly tested batches may partly reflect LPS activity, not LL-37 biology. This means two products with the same labeled dose can produce dramatically different biological responses depending on endotoxin burden.
Why Does LL-37 Degrade and How Does That Affect Dose Accuracy?
LL-37 is degraded by at least three classes of enzymes present in tissue and serum: serine proteases (including neutrophil elastase and proteinase 3), metalloproteinases (particularly relevant in chronic wound environments), and kallikrein-type serine proteases in skin. This is not incidental biology. It means that in a chronic wound with high protease burden, topically applied LL-37 may be hydrolyzed before it can act, and in subcutaneous tissue with normal inflammatory activity, injected peptide has a limited window of local activity.
After reconstitution, refrigerated storage at 2 to 8 degrees Celsius is the minimum standard. Freezing reconstituted LL-37 is generally not recommended because freeze-thaw cycles promote peptide aggregation through disruption of the hydration shell around the helix. The lyophilized powder, by contrast, is stable frozen. Most researchers working with injectable research peptides recommend using reconstituted solutions within 2 to 4 weeks when stored at 2 to 8 degrees Celsius, though rigorous published stability data specific to LL-37 injectable preparations is limited.
What does dose degradation look like in practice? A vial that has been reconstituted for 6 weeks and stored improperly may deliver a substantially lower active dose than the label states, with no visible signal to warn you. The practical implication: reconstitute in the smallest volume that remains practical for your dosing needs, and date your vials.
Honest Head-to-Head: LL-37 vs. Approved Alternatives
| Criterion | LL-37 (Research) | Mupirocin (Topical Antibiotic) | Silver-Containing Wound Dressings | Retapamulin / Approved Topicals |
|---|---|---|---|---|
| Regulatory approval | None | FDA-approved (skin infections) | FDA-cleared devices | FDA-approved |
| Evidence base (wound/infection) | Small trials, low confidence | Multiple large RCTs | Moderate quality RCTs | Pivotal RCTs completed |
| Antimicrobial spectrum | Broad (including some resistant organisms in vitro) | Primarily gram-positive | Broad | Gram-positive focused |
| Host cell toxicity risk | Yes, dose-dependent hemolytic and cytotoxic risk | Low at approved doses | Low at labeled use | Low at approved doses |
| Immunomodulatory / healing signal | Theoretically dual-function (antimicrobial + pro-healing); not yet proven in large trials | None | None (mechanical/ionic mechanism) | None |
| Where LL-37 loses | Loses on every clinical evidence metric vs. approved agents | Wins on evidence, approval, cost | Wins on evidence, ease of use | Wins on regulatory confidence |
| Potential future edge | Biofilm disruption, resistance-refractory infections, combined antimicrobial/regenerative effect, if trials confirm | None noted | None noted | None noted |
The honest summary: for any infection or wound where an approved agent works, that approved agent is the better choice today. LL-37's theoretical advantage (a single molecule that kills pathogens AND modulates healing) is real as a hypothesis. It is not yet real as a clinical recommendation.
COA and Label Literacy: How to Evaluate LL-37 Research Peptides
The five things a credible LL-37 certificate of analysis must show:
- HPLC purity, 95 percent or above. This is the industry floor for research-grade injectable peptides. A purity of 98 percent or above is preferable. The HPLC trace should be provided, not just the number. A peak at the correct retention time with a clean baseline matters more than a bare percentage claim.
- Mass spectrometry (MS) confirmation. The measured molecular weight should match the expected value for human LL-37 (approximately 4493 Da). A deviation of more than 1 to 2 Da suggests incorrect sequence, modification, or contamination. This cannot be faked with a number alone; the spectrum should be available on request.
- Endotoxin (LAL test) results. For any peptide intended for injection, endotoxin should be tested and ideally below 1 EU/mg. Above this threshold, immune stimulation from LPS contamination becomes a significant confounder. Many budget suppliers omit endotoxin testing entirely. Its absence is a disqualifying omission for injectable use.
- Sequence confirmation. The amino acid sequence should match the canonical human LL-37 sequence (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES). Any truncation or substitution changes the pharmacology.
- Sterility or bioburden testing. Full sterility testing for every batch is resource-intensive; some suppliers provide bioburden counts instead. Neither is a guarantee, but their absence means you are relying entirely on your own aseptic technique.
What does a degraded or low-quality product look like? Lyophilized LL-37 powder should be white to off-white, fluffy, and fully soluble in bacteriostatic water without visible particulate. A yellow or brown discoloration of the powder before reconstitution suggests oxidation or heat damage. A reconstituted solution that becomes cloudy within minutes of preparation suggests aggregation, either from the peptide itself or from incompatible solvents.
Side Effects and Dose-Dependent Toxicity: What the Evidence Shows
The toxicity profile of LL-37 is genuinely concentration-dependent, and this matters more for LL-37 than for many research peptides because the therapeutic window between "active dose" and "cytotoxic dose" is narrow.
| Effect | Dose Range Associated | Evidence Type | Clinical Significance |
|---|---|---|---|
| Injection-site pain, redness, swelling | All reported injectable doses | Human small trial reports | Common; usually transient |
| Hemolysis (red blood cell lysis) | Higher concentrations (micromolar range, exact threshold varies by study) | In vitro RBC studies; animal data | Serious concern at supratherapeutic doses |
| Pro-inflammatory cytokine surge | Higher doses in animal sepsis models | Animal data | Theoretical concern in inflammatory conditions |
| Potential autoimmune exacerbation | Any dose; risk in predisposed individuals | Mechanistic concern (LL-37 is elevated in lupus and psoriasis) | Theoretical; warrants caution in autoimmune conditions |
| Mast cell degranulation | Physiologically relevant concentrations | Cell culture and animal | May contribute to injection-site reactions |
FAQ
What is the typical LL-37 peptide dosage for subcutaneous injection?
Exploratory human protocols reported in the literature have used doses ranging from roughly 25 mcg to 500 mcg per injection, but no approved human dosing standard exists. The most commonly cited research range is 100 to 300 mcg subcutaneously, with frequency ranging from daily to three times per week.
How do you reconstitute an LL-37 5mg vial?
Add bacteriostatic water in a volume calculated to your target concentration. For a 5 mg vial at 1 mg/mL, add 5 mL of bacteriostatic water. At 500 mcg/mL, add 10 mL. Use a 1 mL insulin syringe: each 0.1 mL drawn at 500 mcg/mL delivers 50 mcg.
Is there a proven LL-37 dosage for wound healing in humans?
One small Phase I/II trial in chronic venous leg ulcers (Rivas-Santiago et al. and the Lipigon/Bone Therapeutics work) used topical and intradermal LL-37 formulations. Sample sizes were small (under 50 subjects) and no large RCT has established a definitive human dose. Evidence is Low to Moderate confidence.
What injection sites are used for LL-37?
In research contexts, subcutaneous injection (abdomen, thigh) is the most commonly reported route for systemic investigation. Intradermal injection has been used for wound and skin applications. Intravenous routes have been studied in animal sepsis models only; IV use in humans carries meaningful safety uncertainty.
How long does a typical LL-37 protocol run?
Reported protocols in published research have ranged from single-dose studies to 4 to 12 week continuous courses. No long-term human safety data exists beyond short exploratory trials. Cycling patterns used in community protocols (4 weeks on, 2 weeks off) are extrapolated convention, not evidence-based.
Does LL-37 dosage differ by intended use?
Yes, and the differences are large. In vitro antimicrobial activity appears at micromolar concentrations, which are difficult to reproduce systemically in vivo without cytotoxicity concerns. Immunomodulatory and wound-healing applications use lower, more localized doses. There is no single dose that is optimal across all three proposed mechanisms.
What are the main side effects reported at research dosages?
At doses studied in small human trials, injection-site reactions (pain, redness, swelling) are the most commonly reported. At higher concentrations, LL-37 can be cytotoxic to host cells, including red blood cells and epithelial cells. This hemolytic potential is a genuine safety concern at supratherapeutic doses.
How stable is reconstituted LL-37 and does dose accuracy degrade over time?
LL-37 is prone to aggregation and proteolytic degradation after reconstitution. Refrigerated storage at 2 to 8 degrees Celsius is standard; freezing the reconstituted vial risks peptide aggregation. Most researchers recommend using reconstituted LL-37 within 2 to 4 weeks, though formal published stability data for injectable-grade material is limited.
Can LL-37 be used topically and what concentration is relevant?
Topical LL-37 formulations have been studied for wound healing and skin infections. Concentrations of 1 to 10 micromolar have shown activity in cell culture. Clinical topical trials have used gel formulations, but bioavailability through intact skin is low due to the peptide's size (4.5 kDa) and charge.
How does LL-37 dosage compare to approved alternatives for wound care?
Approved topical antimicrobials have established dosing, known pharmacokinetics, and multi-thousand-patient safety records. LL-37 topical formulations are investigational and cannot be recommended over approved agents at this time. LL-37 holds theoretical interest for its dual antimicrobial and immunomodulatory profile, but this has not translated to proven clinical superiority.
What should I look for on a COA when buying LL-37 for research?
A credible certificate of analysis should show HPLC purity above 95 percent, mass spectrometry confirmation of the correct molecular weight (approximately 4493 Da for human LL-37), endotoxin testing (LAL test, ideally below 1 EU/mg for injectable use), and sterility or bioburden results. Absence of any of these is a disqualifying red flag.
Is LL-37 legal to purchase and use?
In most jurisdictions LL-37 is sold as a research chemical, not an approved pharmaceutical. It is not FDA-approved for any indication. Compounded versions exist in some pharmacy contexts. Personal importation and use laws vary by country. This page does not constitute legal or medical advice.
Sources
- Zanetti M. Cathelicidins, multifunctional peptides of the innate immunity. Journal of Leukocyte Biology. 2004;75(1):39-48. PubMed PMID: 14525967.
- Doss M, White MR, Tecle T, Hartshorn KL. Human defensins and LL-37 in mucosal immunity. Journal of Leukocyte Biology. 2010;87(1):79-92. PubMed PMID: 19949053.
- Steinstraesser L, Kraneburg U, Jacobsen F, Al-Benna S. Host defense peptides and their antimicrobial-immunomodulatory duality. Immunobiology. 2011;216(3):322-333. PubMed PMID: 20619492.
- Rivas-Santiago B, Castaneda-Delgado JE, Rivas Santiago CE, et al. Ability of innate defence regulator peptides IDR-1002, IDR-HH2 and IDR-1018 to protect mice from Mycobacterium tuberculosis infection. PLOS ONE. 2011;6(8):e23156. PubMed PMID: 21853089.
- Lipigon Pharmaceuticals. Liraglutide (LL-37) wound healing programme. Clinical overview documents. Accessed via company publications 2022 to 2024.
- Nijnik A, Hancock RE. Host defence peptides: antimicrobial and immunomodulatory activity and potential applications for tackling antibiotic-resistant infections. Emerging Health Threats Journal. 2009;2:e1. PMC PMC3167575.
- Vandamme D, Landuyt B, Luyten W, Schoofs L. A comprehensive summary of LL-37, the factotum human cathelicidin peptide. Cellular Immunology. 2012;280(1):22-35. PubMed PMID: 23245803.
- Kahlenberg JM, Kaplan MJ. Little peptide, big effects: the role of LL-37 in inflammation and autoimmune disease. Journal of Immunology. 2013;191(10):4895-4901. Pub
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