LL-37 is a cathelicidin peptide used for antimicrobial & healing. LL-37 is a natural 37-amino-acid antimicrobial peptide, part of your innate immune system's first line of defense. In plain terms: it punches holes in bacteria and helps wounds heal, which is why it is explored for stubborn infections, though human data is limited.

How much water do I add to LL-37?

You can reconstitute LL-37 with 0.5, 1, or 2 mL of bacteriostatic water. Each option produces a different concentration and syringe draw for the same dose. Use the calculator to see which is easiest to measure.

What does LL-37 cost per dose?

Cost per dose depends on vial size, price paid, and your dose. Enter your vendor's price in the LL-37 calculator to see cost per dose and monthly cost.

What is the reference dose for LL-37?

The commonly referenced range is 0.1 up to 0.5 mg per dose (start low, increase slowly), taken daily, short courses. This is reference information, not a recommendation. Talk to a licensed clinician.

What are the side effects of LL-37?

Reported side effects of LL-37 include: It can irritate the injection site, with a theoretical autoimmune concern, and there is little human data.. Severity and frequency vary by person and dose.

Who should not take LL-37?

LL-37 is generally not appropriate for: No established systemic safety profile; Pregnancy; Autoimmune conditions, as a theoretical precaution. Talk to a licensed clinician before starting.

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Decoding

LL-37_Dosage, benefits & legal status

Also known as cathelicidin, hCAP-18

By the Peptide Decoding Editorial Team

Published July 22, 2026 · Updated July 25, 2026

A natural germ-fighting peptide for stubborn infections and wound healing.

Antimicrobial & healingCathelicidin peptideResearch only

InImmune support

Common vial size5 mg

Dose0.1 up to 0.5 mg per dose (start low, increase slowly)

FrequencyDaily, short courses

RouteUnder the skin (subcutaneous)

StatusResearch only

MixYour choice, calculate it

CycledTaken in daily, short courses

Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.

What is LL-37?

Plain language first. The technical label stays, but it never stands alone.

Overview

It punches holes in bacteria and helps wounds heal. That is why it is explored for stubborn infections. Human data is limited.

The technical version

LL-37 is a natural 37-amino-acid antimicrobial peptide, part of your innate immune system's first line of defense.

What it's used for

A natural germ-fighting peptide used against stubborn infections, biofilms, and gut bugs, and to support wound healing.

How does LL-37 work?

What it does in the body, and where.

LL-37 is part of your innate immune system, the fast general-purpose defence that acts before your body has identified what it is fighting.

01
It physically disrupts bacterial membranes
Rather than interfering with bacterial chemistry, it punches holes in the cell wall, which is why resistance to it develops slowly.
02
It also signals wound repair
Recruiting immune cells and promoting new blood vessel growth at the site.
03
It is not selective about which membranes
At higher concentrations it damages human cells too, which is the central difficulty in developing it as a drug.
04
Human evidence is minimal
Small studies in wound healing. Nothing establishing systemic use.

Where it acts

Skin

Where this compound is thought to act.

What else is it used for?

Each use below carries its own evidence level. Approved means regulators have cleared it for that purpose. Investigational means it is in trials. Early research means it is being studied and is not established.

Stubborn bacterial infections and biofilmsEarly research
Wound healingEarly research
Gut infections, which is a common reason people seek it outResearch only

The published record

Research index

4,556

Records indexed for LL-37400 papers and 34 trials indexed in detail.

252 in humans, 155 of them original studies.

34 registered trials, 7 with posted results.

FDA: Nominated but withdrawn; previously category 2.

Browse the records

In animalsPro

In the labPro

ReviewsPro

Senior author sharePro

Counted from Europe PMC indexing, not read by a person. Human means indexed under humans, which includes reviews and work on human cells. Original studies exclude reviews and lab work on human cells.Last updated 11 September 2026.

Compound field notes

At a glance

Four things to know about LL-37

Evidence

Research only

How much, and do you cycle it?

The range, and whether you take breaks.

0.1 up to 0.5 mg per dose (start low, increase slowly), daily, short courses. Taken in daily, short coursesCommunity practice

Course dosing is how this one is normally used. Where the course length comes from is the thing to check: for most compounds in this pattern it is convention rather than a tested schedule.

Compare this against the whole library →

How long does it stay in the body?

The half-life, and where the figure comes from.

Nothing publishedNo figure

Described as short-lived in the literature without any number attached. No study has measured it.

You can compare this against the whole library to see where it sits.

How do I dose and price it?

Enter your vial and your dose. Pick a mix. We show the draw and the cost.

The vial holds a fixed amount of drug. Adding more water does not make more drug, it just spreads it thinner, so you draw a bigger number on the syringe for the same dose.

Your vial size (mg)

Printed on the vial.

What you paid per vial

Used for cost per dose only.

Your dose (mcg)

Commonly referenced range: 0.1 up to 0.5 mg per dose (start low, increase slowly)Community practice

Choose your mix

0.5 mL water1units · 10 mg/mL

Half a 100-unit syringe

1 mL water2units · 5 mg/mL

One full 100-unit syringe

Easiest

2 mL water4units · 2.5 mg/mL

Two full 100-unit syringes

your own mL

units · —

Enter your own volume

Measuring the water1 mL = one full 100-unit syringe.

Your draw

4 / 100 units

4 units is a very small line to read, so a small slip is a large error. A larger water volume above spreads the same dose across more units.

Full calculator with reorder date →Read a syringe →

What it costs

LL-37 starts at $35.79 across 26 vendors, typically $8.00 – $17.20 per mg.

33 listings, last read Sep 5, 2026. Shipping and card fees are not included.

See all 33 listings →

How do you store it?

Before mixing, and after.

Dry powder in the freezer or fridge. Once mixed, fridge, and use within about a month.

Unmixed lyophilized LL-37 keeps for a long time cold. Once you add water the clock starts: most reconstituted vials hold up for roughly 28 to 30 days at fridge temperature. Keep it out of light, and do not freeze it after mixing.

What are the side effects and cautions?

Known cautions and warnings for this compound.

Who should avoid it

Check these before anything else.

No established systemic safety profile
Pregnancy
Autoimmune conditions, as a theoretical precaution

Stop and get help

These are emergencies. Seek care.

Signs of an allergic reaction
A spreading rash or worsening inflammation

Common effects

Expected, and usually mild.

Injection-site irritation
Only small local experimental human studies exist
Research also notes it can be pro-inflammatory and may have pro-tumour effects in some settings

What regulators say

FDA: Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (category 2 and withdrawn nominations), current as of April 22, 2026
Nominated but withdrawn; previously category 2
Nonclinical findings suggest detrimental effects on male reproduction and protumorigenic effects in some tissues
Checked 11 September 2026

Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.

Is LL-37 approved?

And where the numbers on this page come from.

No. LL-37 is not approved for any use, anywhere. It is sold labelled for laboratory research only, and there is no legal route to buy it for human use.

Approval status
Research only
Route
Under the skin (subcutaneous)
Checked
September 2026

What has happened recently

We have not yet written a full regulatory note for this compound. The status above is current as of the date shown.

You can compare this against the whole library, or read how to check a seller.

DoseFrom research and community reports. No regulator has reviewed this dose.
Vial sizeFrom what vendors typically list; not a recommendation.
Sources
HEAL LL-37, phase 2b randomized placebo-controlled trial in hard-to-heal venous leg ulcers Gronberg et al., first-in-man randomized placebo-controlled trial of LL-37 in venous leg ulcers Randomized double-blind trial of LL-37 cream in diabetic foot ulcer FDA, bulk drug substances for compounding that may present significant safety risks
Reviewed8 September 2026

What else is like LL-37?

Others in Immune support, side by side.

If you're weighing LL-37, it's worth reading Thymulin, Thymogen, and Thymopentin (TP-5) in the same class.

YOU ARE HERE

LL-37

A natural germ-fighting peptide for stubborn infections and wound healing.

Research only

Dose: 0.1 up to 0.5 mg per dose (start low, increase slowly)
How often: Daily, short courses

THYMU

Thymulin

A thymus peptide studied for immune balance and calming inflammation.

Research only

Dose: 1 mg per dose
How often: Daily/weekly

THYMO

Thymogen

A short immune bioregulator taken in courses, with thin evidence.

Research only

Dose: Varies (course-based)
How often: Courses

TP-5

Thymopentin (TP-5)

Five amino acids that carry the whole activity of a thymus hormone.

Clinical use

Dose: 50 mg per dose
How often: 3x per week

See other immune support

Compared with

Thymosin Alpha-1 vs LL-37

One is approved in 35 countries and its largest trial found nothing. The other has never been injected in a published study.

Read comparison →

Guides for this compound

How to Reconstitute a Peptide
Mix peptide powder with bacteriostatic water, step by step.
How to Read an Insulin Syringe
Read the units, convert to millilitres, and draw the exact dose.
mcg vs mg: The Peptide Dosing Mistake to Avoid
Your vial says mg and your protocol says mcg. Here is the conversion and how to check it.
How to Read a Peptide COA
What the purity number does and does not tell you, and how to spot an edited report.
How to Vet a Peptide Vendor
Independent COAs, HPLC purity, and the red flags that mean walk away.

Sources

HEAL LL-37, phase 2b randomized placebo-controlled trial in hard-to-heal venous leg ulcers(2021)
148 patients, topical LL-37 at two concentrations against placebo. No significant improvement in healing across the full study population. A post hoc subgroup with wounds of at least 10 cm2 showed benefit, which the authors themselves describe as warranting a properly powered study.
Gronberg et al., first-in-man randomized placebo-controlled trial of LL-37 in venous leg ulcers(2014)
34 participants, twice weekly topical application at three concentrations. The earlier positive result that the larger 2021 trial did not reproduce.
Randomized double-blind trial of LL-37 cream in diabetic foot ulcer(2023)
LL-37 cream improved healing rate in mildly infected diabetic foot ulcers but did not reduce IL-1a, TNF-a or aerobic bacterial colonisation. Registered as NCT04098562.
FDA, bulk drug substances for compounding that may present significant safety risks(2026)
FDA cites immunogenicity risk for certain routes and complexities with peptide-related impurities and characterisation, and says it lacks sufficient safety information to know whether the drug would cause harm in people. It goes further than it does for most entries on this page: it states that nonclinical research findings suggest detrimental effects on male reproduction, and that the compound can be protumorigenic in some tissues. As of the 22 April 2026 version of this page, the substance sits in the second table, headed bulk drug substances nominated but withdrawn, rather than in the live category 2 list. The nomination was withdrawn, which is not the same as being approved or cleared: FDA still publishes the safety language above, and no longer has a nomination in front of it to evaluate.

Last reviewed 8 September 2026

Beyond these, 434 records are indexed. Browse the records