If my body already makes it, is it safe to add more?

That reasoning does not hold here. The body regulates LL-37 tightly and releases it locally where it is needed, and the conditions where it is elevated systemically, rosacea and psoriasis and lupus, are diseases rather than states of enhanced immunity.

Does it work against antibiotic-resistant bacteria?

In the laboratory, against many of them, and against biofilms too. That is a genuine and important property. It has not been shown to treat an infection in a person, and no trial has tested it.

What is the vitamin D connection?

The gene for LL-37 carries a vitamin D response element, so your own production depends on vitamin D status. It is one of the better-established links between vitamin D and immune function, and it argues for correcting a deficiency instead of injecting the peptide.

Healing & recovery

LL-37

Cathelicidin LL-37 · hCAP18 · CAMP peptide

Early human trialsReviewed 16 Aug 2026

LL-37 is not a designed drug. It is a peptide your own body makes — the only cathelicidin humans produce — released by neutrophils and epithelial cells as part of the innate immune response. It kills bacteria by physically disrupting their membranes, and it signals to immune cells at the same time.

The reason it attracts interest is that membrane disruption is a hard mechanism for bacteria to develop resistance against. Where an antibiotic interferes with a specific bacterial enzyme, LL-37 punches holes in the membrane itself, and it also penetrates biofilms that conventional antibiotics struggle with. In an era of resistant infection that is a valuable property.

It also has a second literature that anyone considering it should read first. Excess LL-37 is implicated in the pathology of rosacea, psoriasis and lupus. In those conditions the problem is too much of this peptide — not too little — and its ability to bind self-DNA and trigger interferon responses is part of what drives the autoimmunity. This is a compound the body regulates carefully, and the case for adding more to a healthy person is not obvious.

How it works

LL-37 is amphipathic, one face charged and one face fatty, which lets it insert into bacterial membranes and destabilise them. Bacterial membranes carry more negative charge than human ones, which is what gives it selectivity, though that selectivity is relative rather than absolute.

Beyond killing bacteria directly, it acts as a signalling molecule: recruiting neutrophils and monocytes, promoting angiogenesis and re-epithelialisation in wounds, and neutralising bacterial endotoxin. Much of the wound-healing interest rests on these effects rather than on the antimicrobial one.

The same properties drive the disease side. LL-37 binds self-DNA released by dying cells and forms complexes that activate plasmacytoid dendritic cells through TLR9. That is a route to sustained interferon signalling, and a recognised mechanism in psoriasis and lupus. It is elevated in rosacea lesions, and the abnormal processing of it there is considered causal rather than incidental.

Vitamin D controls its expression. The gene carries a vitamin D response element, which is one of the better-established mechanistic links between vitamin D status and innate immune function. It is also a reason correcting a deficiency has an evidence base that injecting the peptide does not.

Quick reference

Commonly described dose: 500 mcg–3.2 mg
How often: Applied to the wound twice weekly in the trial protocol
Route: Topical or Subcutaneous
Where: Directly to the wound, Abdomen, Thigh
Timing: No timing effect established.
Storage once mixed: Refrigerated, 14 days

These describe what sources report, not what you should do. Full detail and provenance in the dosing section below.

Price index

Per-milligram pricing across vendors arrives with the directory. We are recording prices now so the history exists when the page ships.

Vocabulary on this page

Concentration: How much peptide there is in each millilitre of solution, once the vial has been reconstituted.
Research chemical: A legal label, not a quality grade. It describes what a seller is permitted to sell you, and says nothing about what is in the vial.
Vial: The small sealed glass container a peptide is sold in, holding a stated mass of freeze-dried powder under a rubber stopper.
Injection site: Where on the body an injection is given. Rotating between sites is standard practice for anything given repeatedly.
Peptide: A short chain of amino acids: the same building blocks as a protein, in a chain short enough to behave differently.

The whole glossary →

Regulatory status — United States

Not approved for human use in any jurisdiction. A synthetic version has reached small phase 2 study as a topical wound treatment. Injected LL-37 has never been studied in a human trial, and is sold only as a research chemical.

Last reviewed 16 Aug 2026. Regulatory positions in this category change frequently; we date this line so you can see how current it is.

What it is studied for

Each entry states the evidence behind it. We do not rank indications by effectiveness — for most compounds here, that would be a claim nobody can support.

Wound healing, including chronic ulcers

Clinical trial

The application with actual human data behind it.

EvidenceA small phase 2 trial of topical LL-37 in venous leg ulcers reported improved healing against placebo. Topical application to a wound, not systemic injection.

Antimicrobial and antibiofilm activity

Published review

The best-characterised property.

EvidenceExtensively demonstrated in laboratory studies against a wide range of bacteria and against biofilms. No human trial has established it as a treatment for infection.

Systemic immune support

Community practice

Why it is bought as a research chemical.

EvidenceNo human trial has studied injected LL-37 for this or any systemic purpose. The known disease associations point the opposite way.

Identity and clearance

Molecule

Class: Human cathelicidin antimicrobial peptide
Molecular weight: 4493.3 Da
Length: 37 amino acids

Named for its two leading leucines and its 37 residues. Cleaved from a larger precursor, hCAP18, at the site of action.

Dose protocols reported in sources

Displayed for reference only. Every row says where it came from, and a trial protocol and a community convention are not the same kind of information. None of this is fed into the calculator, and none of it is a recommendation.

Dose protocols reported in sources, with the source of each.
Goal	Dose	Frequency	Route	Units, 5 mg vial	Source	Start this protocol
Topical application, as studied	500 mcg – 3.2 mg	Applied to the wound twice weekly in the trial protocol	TopicalThe phase 2 trial applied it directly to venous leg ulcers as a gel. This is the only dosing with human evidence behind it, and it is not an injection.	from 50 u	Clinical trial	Start this
Commonly described community protocol, injected	100 mcg – 500 mcg	Daily, in short courses	SubcutaneousNo trial supports injecting LL-37 at any dose. These figures come from community discussion, and the peptide's role in autoimmune disease is a specific reason to treat systemic exposure differently from topical.	10–50 u	Community practice	Start this

Start this copies a row into a protocol of your own, which you can then edit. Where a source gave a dose range or an ambiguous frequency, those fields arrive empty — we will not pick a number on your behalf.

CheckRows marked community practice describe what people commonly do, drawn from public discussion. They are not derived from any trial and are not evidence that a dose is safe or effective.

Calculator

Work out what to draw

Pre-filled with a 5 mg vial as a worked example. These are not recommended values — change them to match the vial in front of you.

Draw to 8 units on a 1 mL U-100 syringe. That is 0.08 mL, containing 200 mcg of LL-37.

Concentration2.5mg / mL

Volume drawn0.08mL

Doses per vial25doses

Per unit25mcg / unit

8 units sits exactly on a printed line.

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Bioalmanac performs arithmetic on values you enter. It does not recommend doses, schedules or compounds, and nothing here is medical advice. Confirm every calculation against your vial and syringe before drawing, and speak with a licensed healthcare provider.

Open this calculation in the full calculator

Units, concentration, bacteriostatic water — the glossary defines the vocabulary, and a unit is not a fixed volume.

Safety

Reported effects

Injection site irritationCommunity practice
Commonly reported
A membrane-disrupting peptide is inherently irritating to the tissue it is injected into.
Potential to worsen autoimmune and inflammatory skin diseasePublished review
Mechanistically expected
Elevated LL-37 is part of the pathology of rosacea, psoriasis and lupus, not a treatment for them. This is the distinctive risk here, and it comes from disease biology rather than from adverse event reports.
Haemolysis at high concentrationsPublished review
Demonstrated in laboratory studies
Selectivity for bacterial over human membranes is relative, not absolute. At sufficient concentration it damages red blood cells too.
Systemic effects of injected LL-37Community practice
Unknown
Never studied in a human trial by any systemic route.

When to stop

Any flare of rosacea, psoriasis, eczema or another inflammatory skin condition.
New or worsening joint pain, rash or fatigue. LL-37 is implicated in lupus pathology, and this is how that presents.
An injection site that becomes hot, spreading or produces pus.
Any allergic response: rash, hives, facial swelling or difficulty breathing. Seek urgent care.
Dark urine or unusual fatigue, which could indicate red cell damage.

Interactions and situations that need care

Rosacea, psoriasis, lupus or other autoimmune diseaseAvoid
Excess LL-37 is part of the mechanism of these conditions, not a treatment for them. In rosacea it is elevated in lesional skin; in psoriasis and lupus it forms complexes with self-DNA that sustain interferon signalling. Adding more is pointing the intervention the wrong way.
Active infection being treated with antibioticsUse caution
Nothing establishes how injected LL-37 interacts with antibiotic therapy, and substituting an unstudied research chemical for a treatment that works is how a treatable infection becomes a serious one.
Pregnancy and breastfeedingAvoid
No reproductive or developmental safety data.

What to expect

HonestlyThere is no human efficacy data for this compound, so there is no evidence-based timeline to give. Any site publishing a week-by-week schedule of expected effects has invented it.

The only human evidence is a small trial of topical application to leg ulcers. There is none at all for injecting it.
The antimicrobial and biofilm activity is real and well demonstrated, in the laboratory. That is a long way from a treatment for an infection in a person.
Excess LL-37 causes disease. Rosacea, psoriasis and lupus all involve too much of it, which is an unusual and important counterpoint for a compound sold as immune support.
If the vitamin D connection is what interests you, correcting a deficiency raises your own LL-37 through the normal regulated pathway and has an evidence base this does not.
It adsorbs strongly to plastic, so an unknown fraction of a reconstituted dose may never leave the vial.

Storage and handling

Freeze-dried powder: Refrigerated at 2–8 °C, protected from light.
After mixing: Refrigerated at 2–8 °C. Do not freeze once mixed. LL-37 adsorbs to plastic, so a substantial fraction can be lost to the walls of the container. Glass is preferable.
Long-term, frozen: Unopened powder is stable at −20 °C or colder.

Printable one-pager How to reconstitute a vial, step by step

Checking your vial

Research chemicals carry no manufacturing standard, so what the vial looks like is often the only quality signal available before you use it. More on assessing quality and COAs.

White cake, clear solution
Standard for a lyophilised peptide of this size.
Cloudy solution or visible aggregate
Amphipathic peptides aggregate readily. Cloudiness means it has, and the aggregate is not active.

Questions

If my body already makes it, is it safe to add more?: That reasoning does not hold here. The body regulates LL-37 tightly and releases it locally where it is needed, and the conditions where it is elevated systemically, rosacea and psoriasis and lupus, are diseases rather than states of enhanced immunity.
Does it work against antibiotic-resistant bacteria?: In the laboratory, against many of them, and against biofilms too. That is a genuine and important property. It has not been shown to treat an infection in a person, and no trial has tested it.
What is the vitamin D connection?: The gene for LL-37 carries a vitamin D response element, so your own production depends on vitamin D status. It is one of the better-established links between vitamin D and immune function, and it argues for correcting a deficiency instead of injecting the peptide.

References

Topical LL-37 in hard-to-heal venous leg ulcers: a randomised, placebo-controlled phase 2 trial
Wound repair and regeneration literature, 2014 · Randomised, double-blind, placebo-controlled phase 2 trial
Adults with chronic venous leg ulcers · n = 34 · 0.5 to 3.2 mg applied topically, twice weekly · 4 weeks
Improved ulcer healing at lower doses against placebo, with the highest dose performing less well, suggesting a therapeutic window, not a dose-response. A small trial, and the only human efficacy data for the compound.
Cathelicidin LL-37: antimicrobial mechanism and immune signalling
Immunology review literature, 2020 · Review
Humans, animals and in vitro
Summarises membrane-disrupting antimicrobial activity, antibiofilm effects and immunomodulatory signalling, and notes haemolysis at higher concentrations as evidence that selectivity for bacterial membranes is relative.
LL-37 in rosacea, psoriasis and lupus: the peptide as a driver of disease
Dermatology and rheumatology literature, 2019 · Review of mechanistic and clinical findings
Humans
Documents elevated LL-37 in rosacea lesions and its role in forming self-DNA complexes that sustain interferon signalling in psoriasis and lupus. Establishes excess LL-37 as causal in these conditions rather than incidental.
Commonly reported community protocols
Bioalmanac editorial summary of public community sources, 2026 · Not a study
Records injected dose patterns described in public discussion. No trial supports any of them, and they carry no evidential weight about safety or effect.

Related compounds

BPC-157

A synthetic 15-amino-acid peptide studied in animals for effects on tendon, ligament and gut tissue repair. No completed human trials.

TB-500

A synthetic fragment of thymosin beta-4, a naturally occurring protein involved in cell migration and tissue repair. Animal evidence only.

GHK-Cu

A naturally occurring copper-binding tripeptide with a long history in topical skincare research. Injected use is not what the research studied.

KPV

A three-amino-acid fragment of alpha-MSH studied for anti-inflammatory effects, largely in animal models of gut inflammation.

Keep this page honest

If something here is wrong, out of date, or missing a source, tell us and we will fix it and say that we did.

Suggest a correction

This page is educational. It describes what published research reports, not what you should do. Peptides discussed here are largely not approved for human use, and nothing on Bioalmanac is medical advice. No clinician reviews these pages.

Page last updated 16 Aug 2026