LL-37
Also known as: Cathelicidin antimicrobial peptide, CAP-18 fragment
LL-37 is a naturally occurring human antimicrobial peptide derived from cathelicidin, studied in the laboratory for immune and antimicrobial roles. It is a research peptide and is not approved for human use in Australia.
- Category
- Immune / Antimicrobial
- Reported half-life
- Not well established
- Common forms
- Lyophilised powder for reconstitution (research preparations)
- Research status
- A naturally occurring human antimicrobial peptide studied in laboratory and animal research; it is a research peptide and is not approved for human use in Australia.
- Last updated
- 21 June 2026
Claimed effects
The following effects are reported or claimed by users and in early research. They are not established medical facts and many are not supported by large human trials.
- Reported to have antimicrobial activity in laboratory studies
- Reported to be associated with immune-modulating processes in research
- Reported to be studied in relation to wound-healing-related pathways
How it is reported to work
LL-37 is the active fragment of human cathelicidin and is proposed to disrupt microbial membranes while also interacting with immune-signalling pathways. These proposed mechanisms come largely from in vitro and animal research and should be regarded as preliminary rather than established for any human therapeutic use.
Background
LL-37 is the active fragment of human cathelicidin, a naturally occurring antimicrobial peptide that is part of the innate immune system. This page is educational information, not medical advice, and the effects described below are reported claims, not established facts.
What the research shows
Most published research on LL-37 consists of laboratory and animal studies exploring antimicrobial and immune-related activity. These suggest possible roles in host defence, but the body of human evidence is limited and not translated into approved therapy.
| Evidence type | Status |
|---|---|
| Laboratory (in vitro) studies | Present |
| Animal studies | Present |
| Large human clinical trials | Limited |
| Australian approval | None |
What people use it for (reported)
Online, people report interest in LL-37 in connection with immune and antimicrobial topics, sometimes alongside other immune-related peptides. These are anecdotal reports, not validated clinical outcomes, and they have not been confirmed in controlled human trials. Nothing here should be read as encouragement to use it for any purpose.
Things to be aware of
LL-37 is not approved for human use in Australia. Its safety profile in humans is not well understood, and grey-market preparations cannot be verified for purity or identity by sight. If you have an infection or immune-related concern, the appropriate step is to speak with a qualified healthcare professional. This article does not recommend obtaining or using LL-37. All effects described here remain reported claims, not established facts.
Reported positives & side effects
Compiled from research and community reports. These are reported outcomes, not guarantees or medical advice, individual experiences vary widely.
Reported positives
- Reported in laboratory research to show broad antimicrobial activity
- Reported to be associated with immune-modulating effects in studies
- Reported interest in wound-healing-related pathways in research
- Reported to be a naturally occurring component of human innate immunity
Common side effects
- Reported injection-site redness, pain or irritation
- Reported localised swelling at the injection site
- Reported flu-like or general malaise sensations anecdotally
- Reported transient histamine-like flushing
Rare / serious side effects
- Reported allergic or hypersensitivity-type reactions
- Reported pro-inflammatory effects that may worsen some conditions
- Reported concern that unverified product purity could cause unpredictable reactions
Reported misuse & overdose risks
What has been reported to happen with overuse, excessive dosing, or long-term misuse of LL-37. Listed so you can make an informed decision, not to suggest any use is safe.
- Reported self-dosing for unproven infection or autoimmune indications without medical oversight
- Reported use of unverified grey-market product whose identity and purity cannot be confirmed
- Reported escalation of dose beyond any researched range in search of stronger effects
- Reported repeated use that may, paradoxically, drive inflammation given its immune-signalling role
Reported results timeline
Roughly how long people report it takes to notice effects. A general guide from reports, not a promise, and not advice. Reported onset is described over days to weeks, with no clinically established human timeline.
First effects
any reported local or systemic sensations within days
Noticeable change
reported subjective immune or recovery changes over weeks
Clear results
reported cumulative changes after extended use; not clinically established
Commonly reported dosing & protocol
Reported figures only, NOT a recommendation or dosing advice. These are numbers people report using, compiled for education so you can make an informed decision. We do not advise anyone to take LL-37. Many peptides are not approved for human use in Australia. Speak to a qualified healthcare professional.
| Route | Reported as subcutaneous injection or localised injection (research use) |
|---|---|
| Typical reported dose | Reported around 100-500 mcg per dose; dosing is not well established |
| Frequency | Reported anywhere from daily to a few times weekly in anecdotal accounts; no established schedule |
| Cycle length | No established cycle length; reported short courses of a few weeks in anecdotal accounts |
Reported reconstitution (mg → units)
Reported example: a 5 mg vial plus 2.5 mL bacteriostatic water gives 2 mg/mL. A reported 250 mcg (0.25 mg) dose is about 0.125 mL, which is roughly 12.5 units on a U-100 insulin syringe.
Work out the units for your vial → CalculatorCommonly reported as short daily or several-times-weekly subcutaneous courses over a few weeks; this is reported information, not advice.
Best used with / commonly stacked with
Combinations people report using together. Reported, not recommended, stacking can increase risks.
Reported together for anti-inflammatory and gut-immune interest
Reported together for combined immune-modulation interest
Reported alongside it anecdotally for recovery and tissue-repair interest
Safety notes
LL-37 is a research peptide and is not approved for human use in Australia. Its safety in humans is not well characterised, and grey-market product purity and identity cannot be verified by consumers. Anyone with an infection or immune-related concern should consult a qualified healthcare professional rather than self-experiment.