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Research compound · not FDA-approved

LL-37

Also written LL 37.

LL-37 is a peptide 37 amino acids long that your own white blood cells make. It kills bacteria by breaking open their outer membrane.

What matters first

Why people look it up
It is sold for stubborn infections, for biofilms, and for gut complaints.
What the evidence shows
It has reached people twice in registered work: injected into melanoma deposits, and applied to venous leg ulcers. Neither study tested an infection. On the ulcers the two lower strengths improved healing while the highest did no better than placebo. The FDA cited animal findings of harm to male reproduction, and of tumor-promoting activity in some tissues.
Dose status
LL-37 is not FDA-approved, so no dosing label exists for it. The sections below explain what researchers tested and what remains unknown.

Evidence snapshot

Foreign approval or limited human data

The fastest way to see what kind of evidence this page is built on.

Regulation
Not FDA-approvedNo US prescribing label
Dose source
Human study1 reported dose row
Safety evidence
9 listed safety findingsCommon and serious effects shown apart
Sources
2 cited sourcesMedical review complete · 2026-08-12
Open the shareable evidence image
LL-37 at a glance: foreign approval or limited human data, dosing basis, regulatory status, safety coverage, and cited-source count. These details summarize the available sources; they are not treatment recommendations.

Further down: research and dosing details · how good the evidence is · questions

Medically reviewed by Jennifer Montecillo, MD · non-practicing medical reviewerReviewed 2026-08-12open the primary sources

What is known about LL-37

LL-37 is a 37-amino-acid peptide made by the human immune system. White blood cells store its larger parent protein and release LL-37 across the skin, gut, and airways. It can break open bacterial membranes and signal to immune cells. Registered studies have used it in people twice: injected into melanoma tumors and placed on leg ulcers. Both studies were small, and neither tested the infection and gut uses these vials are sold for.

LL-37 research and regulatory details: evidence quality, approval status, doses, handling, and presentation.
TopicValue
Strongest sourcelimited human data
FDA approvalNot FDA-approved
Studied dosing250–500 mcg once every 7 days for up to 8 weeks, injected into a cutaneous or subcutaneous melanoma deposit (2 participants at 250 mcg, 1 at 500 mcg — 3 treated in all) — from clinical trials
Typical vials5 mg

Every row links back to a source listed below. These facts are for reference, not a personal recommendation.

What the evidence for LL-37 is

People have received this compound in a documented setting, or it has approval outside the United States. The available human evidence is still too limited to show a clear dose-and-result pattern for US use.

limited human data
What it establishes
It shows that people have received it and that some human information exists.
What it does not establish
It does not prove that the same dose is appropriate in the United States or that uncommon and long-term risks are known.

Check the country, study size and reason it was used. Do not treat limited human data as an FDA-approved schedule.

Where LL-37 is in clinical trials

No trial of this compound is registered on ClinicalTrials.gov.

That is worth sitting with. Nobody has registered a study to find out whether LL-37 works in people, so no result is coming and no date is worth waiting for. Sellers are not waiting for that work either.

A registered study means a sponsor filed a plan and started enrolling. It is not evidence the drug works, and most drugs tested in people never reach a pharmacy. Sponsors write and update these sources themselves; the National Library of Medicine publishes them without checking them.

ClinicalTrials.gov · retrieved 2026-08-23

Every compound we track, and what stage each one has reached →

Regulatory status

The body makes LL-37, but that does not make a product approved.

No regulator has approved it as a drug. FDA lists it under substances nominated but withdrawn. The agency cites immune reactions, limited safety data and harm seen in animals.

FDA plans to review LL-37 at a compounding meeting before the end of February 2027. No date or docket exists yet.

Full regulatory tracker →

Where to go next on LL-37

The schedule, the side effects and the mixing math each have their own page.

LL-37 side effects, as the sources describe them

When LL-37 reactions tend to appear, tied to that compound’s own escalation steps.

Convert an LL-37 amount to units on a U-100 barrel

Every step of the LL-37 arithmetic is printed, so the result can be checked by hand.

Choosing a water volume for a 5 mg LL-37 vial

How the water volume changes concentration, draw size and doses per 5 mg LL-37 vial.

Where LL-37 sits among the skin compounds

3 compounds people take for skin, and what each was measured against, with LL-37 as one example

The healing and recovery page LL-37 appears on

3 of the 4 healing and recovery rows rest on reported use and nothing more, with LL-37 as context

Check the same draw on a vial that is not LL-37

Any vial at all, LL-37 among them, with the arithmetic shown rather than hidden.

Compare the LL-37 schedule against the others

The 28 pages with no published schedule are on the table too, including LL-37

The immune support page LL-37 appears on

1 of the 3 immune support rows rest on reported use and nothing more, with LL-37 as context

Registered trials for LL-37 and the rest

Phase, status and the next measurement date for each program, including LL-37

The proceedings behind the LL-37 note on this page

Newest entry first, with LL-37 among them.

Safety notes

  • The human dose on this page comes from 3 people at two dose levels in one trial, injected into tumors rather than into fat
  • That trial ran for five years and enrolled four people. It posted no finding that the drug worked
  • In a larger skin trial, lower strengths helped leg ulcers heal. The highest strength did no better than placebo
  • Raised LL-37 in facial skin is an established mechanism in rosacea — more of this signal is not a neutral proposition
  • FDA cites animal findings of male reproductive harm and tumor growth in some tissues
  • The peptide disrupts lipid membranes, an activity that is not selective for bacterial ones at all concentrations
  • One patient in the melanoma trial grew crops of wart-like skin lesions, and a squamous cell carcinoma was recorded among the three treated people

Questions about LL-37

Is LL-37 FDA-approved?

No. There is no prescribing label for it, so no approved dose exists — the regulatory status section above has the detail.

How is LL-37 taken?

By injection under the skin, once every 7 days.

How does LL-37 differ from the other compounds in this class?

LL-37 has been studied in people, but it works through a different system from GLP-1 and amylin drugs. Its doses and results are not directly comparable with theirs.

What is not known about LL-37?

It does not prove that the same dose is appropriate in the United States or that uncommon and long-term risks are known.

2primary sources, each with the day we read it — open the documents used on this page