LL-37
Taken to fight stubborn infections
Human cathelicidin
Match every finding to its exact substance, formulation, route and study population. A related molecule or approved medicine does not validate a catalog vial.
Simplified drawing of a chain of 37 amino acids
At a glance
Why people take it. And what backs it up.
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Fight stubborn infections
Lab studies only
Taken in small daily shots or nasal sprays, often with thymosin alpha-1, against lingering infections such as Lyme, sinusitis and parasites.
Sources (6)
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ClinicHatter Labs (telehealth clinic), LL-37 Protocol Guide (opens in a new tab)
“LL-37 is suited for individuals dealing with persistent infections, biofilm-related conditions, or compromised innate immunity.”
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ClinicHatter Labs (telehealth clinic), LL-37 Protocol Guide (opens in a new tab)
“Patients with chronic sinusitis or recurrent upper respiratory infections involving bacterial biofilm”
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ForumReddit r/Peptides: “LL-37 first day side effects” (comment, July 2026) (opens in a new tab)
“I used it to clear gut bacteria and that parasite (cylosporiasis) going around and it did work.”
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ForumReddit r/CIRS: “Is VIP nasal spray really necessary?” (comment, June 2025) (opens in a new tab)
“including ll37 for use on MARCONS. I would also add KPV to the nasal spray with the LL37.”
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“B. burgdorferi were killed by the PMNL antimicrobial components elastase, LL-37, bactericidal/permeability-increasing protein, and human neutrophil peptide-1.”
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StudyOverhage et al., Infection and Immunity, 2008 (PubMed abstract) (opens in a new tab)
“In addition to its key role in modulating the innate immune response and weak antimicrobial activity, LL-37 potently inhibited the formation of bacterial biofilms in vitro.”
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Rebalance the gut
People report it, not studied
Some take it for gut bacterial overgrowth and other gut infections, expecting a flu-like ‘die-off’ reaction at first.
Sources (2)
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PractitionerBen Greenfield, ‘Ben’s Peptide Stack’ article (immunity stack) (opens in a new tab)
“Warning: If you have SIBO, the die-off and Jarisch-Herxheimer Reaction from LL-37 can be uncomfortable and may involve flu-like symptoms and diarrhea for up to two weeks.”
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ForumReddit r/Peptides: “LL-37 first day side effects” (comment, July 2026) (opens in a new tab)
“I used it with TA1 for gut issues with a lot of success.”
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Evidence briefing
Sources checkedWhat the sources support.
LL-37 is the 37-amino-acid active fragment of human cathelicidin (hCAP18), part of innate host defense. It remains investigational; FDA says human safety information is inadequate for proposed compounded routes and notes possible immunogenicity, reproductive effects in nonclinical work and protumorigenic effects in some tissues. Online LL-37 vials are not an approved medicine.
Antimicrobial or wound-healing activity in laboratory and topical research does not establish an effective or safe injectable treatment; FDA specifically identifies gaps for proposed routes.
The research. What’s been studied.
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Animal & lab studies
Antimicrobial activity in the lab
Can disrupt some microbes and biofilms in experimental systems; this is not evidence that seller LL-37 treats human infections.
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Early human studies
Topical wound research
A small study examined topical LL-37 for chronic venous leg ulcers. The limited evidence does not establish a standard or broadly effective wound treatment.
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Animal & lab studies
Immune signaling
Participates in innate immune responses in experimental research; effects depend on tissue and context.
What do these labels mean?
- Human evidence: approved-drug data or larger human studies, within the populations and uses studied.
- Early human studies: small, preliminary or limited human studies.
- Animal & lab studies: animal or laboratory findings that do not establish effects in people.
- Unverified: a proposed use or claim without verified supporting clinical evidence.
How each claim was reviewed (4)
Reported effects and evidence.
A citation may support, qualify or correct a claim. Read the study scope; a laboratory result is not an established benefit in people. Each review covers a claim as it was first collected; the tiles above show the collection’s current wording.
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In-vitro microbiology
Review of “Kills bacteria and breaks up biofilms”
LL-37 inhibited Pseudomonas biofilm formation and affected existing biofilms in laboratory experiments.
Limitations and applicability. Verified biofilm effects include mechanisms beyond membrane puncture, and differ from bacterial killing concentrations.
Original collected claim and review history
Original title: Kills bacteria and breaks up biofilms
Punctures bacterial membranes and disrupts biofilms that shield bacteria from antibiotics.
Original label: animal. Preserved for traceability; the reviewed wording above qualifies this record.
Record ll-37:benefit:1 · Annotated 2026-10-01 · Review method
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Human topical trials; larger trial negative overall
Review of “Chronic wound healing”
An early topical study was encouraging, but the larger phase IIb trial found no significant overall healing benefit; subgroup findings were exploratory.
Limitations and applicability. Selective positive summary omits 148-patient phase IIb null result; favorable large-ulcer subgroup was post hoc.
Original collected claim and review history
Original title: Chronic wound healing
A small trial of topical LL-37 healed chronic leg ulcers faster.
Original label: early. Preserved for traceability; the reviewed wording above qualifies this record.
Record ll-37:benefit:2 · Annotated 2026-10-01 · Review method
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Preclinical cell/rodent experiments
Review of “Neutralizes endotoxin”
LL-37 reduced LPS-related effects in cell and rodent experiments.
Limitations and applicability. Endotoxin findings are preclinical and do not establish treatment of infection or sepsis in people.
Original collected claim and review history
Original title: Neutralizes endotoxin
Binds bacterial toxins that drive inflammation.
Original label: animal. Preserved for traceability; the reviewed wording above qualifies this record.
Record ll-37:benefit:3 · Annotated 2026-10-01 · Review method
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In-vitro human-cell chemotaxis
Review of “Recruits immune cells”
LL-37 induced migration of selected human immune cells in laboratory assays.
Limitations and applicability. Human cells in a dish are not a human clinical trial; inflammatory recruitment is not always beneficial.
Original collected claim and review history
Original title: Recruits immune cells
Calls white blood cells to infection sites.
Original label: animal. Preserved for traceability; the reviewed wording above qualifies this record.
Record ll-37:benefit:4 · Annotated 2026-10-01 · Review method
The research in detail
Evidence category
Human trials, not approved
LL-37 has antimicrobial and immune-signaling activity in laboratory studies. A small topical study examined chronic venous leg ulcers, but such work does not establish a reliable treatment effect or validate injectable LL-37. FDA says human safety information for proposed compounded routes is inadequate and notes nonclinical reproductive and tissue-growth concerns.
Evidence is assessed claim by claim above. Regulatory approval, study design, findings and relevance are separate questions; there is no single evidence score.
Risks and unknowns. What to know first.
Collected cautions follow. These are not an exhaustive or independently validated safety assessment; claim references do not automatically support every caution.
- Can cause significant local irritation when injected.
- Because it drives inflammation in autoimmune skin disease, it could worsen those conditions.
What people report
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Regulator
FDA says compounded LL-37 may cause immune reactions against the drug for some routes and may have impurity problems; FDA lacks enough safety information to know whether it harms people. Animal and lab research suggests harm to male reproduction and that it can promote tumors in some tissues (page current April 2026).
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Regulator
In 2020 Tailor Made Compounding, a Kentucky compounding pharmacy that supplied clinics (its peptide catalog is a dose source here), pleaded guilty to distributing unapproved new drugs; per the plea agreement these included LL-37 (with BPC-157, DSIP, epitalon, selank, semax and others), and it forfeited $1,788,906.82.
Source: US Attorney’s Office, Eastern District of Kentucky, press release, Oct 29, 2020 (opens in a new tab)
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User reports
A user reported arthritis in the hip for almost 2 weeks, which they took to be reactive arthritis triggered by LL-37; another user said it gave them temporary reactive arthritis after taking it for psoriasis.
Source: Reddit r/Peptides, ‘Anyone here tried LL-37?’ (comment) (opens in a new tab)
Show all 9 cautionsShow fewer cautions
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User reports
A new user woke after the first dose with joint pain, aches and a burning feeling on the body; another felt noticeably unwell and more tired after starting a second cycle.
Source: Reddit r/Peptides, ‘LL-37 first day side effects’ (opens in a new tab)
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User reports
After 5 days of 200–400 mcg a day during flu (stacked with BPC-157, TB-500 and GHK-Cu), a final 400–500 mcg dose was followed by joint pain, headache, severe weakness, a fall in heart-rate variability and a high resting heart rate; the user was back to baseline after 4 days.
Source: Reddit r/Peptides, ‘LL-37 cumulative overdose’ (opens in a new tab)
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User reports
Ben Greenfield warns that in people with small intestinal bacterial overgrowth (SIBO) the bacterial ‘die-off’ (Herxheimer) reaction can cause flu-like symptoms and diarrhea for up to two weeks.
Source: Ben Greenfield, ‘Ben’s Peptide Stack’ article (opens in a new tab)
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User reports
One user who took 250 mcg three times for libido reported the opposite: sexual anhedonia (unable to climax) lasting at least 3 weeks. Single report.
Source: Reddit r/Peptides, ‘Anyone here tried LL-37?’ (comment) (opens in a new tab)
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Study
A 2007 Nature study found LL-37 turns the body’s own DNA into a trigger for immune (interferon) activation in psoriasis, suggesting it can drive autoimmune skin disease.
Source: Lande et al., Nature 2007 (PubMed 17873860) (opens in a new tab)
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Study
A 2007 Nature Medicine study found people with rosacea have abnormally high cathelicidin (the LL-37 family) in facial skin, and injecting these peptides increased skin inflammation in mice.
Source: Yamasaki et al., Nature Medicine 2007 (PubMed 17676051) (opens in a new tab)
Published dosing records. What the trials used.
Historical label and trial records for the named product, route, population and indication. These records are not a personal schedule or a validated regimen for a catalog vial. Source attribution does not establish applicability.
Phase 1/2 trial
Phase 1/2 trial in people with hard-to-heal venous leg ulcers (Wound Repair and Regeneration, 2014)
Source: Grönberg et al., Wound Repair and Regeneration, 2014 (opens in a new tab)
- Weeks 1–4
- 0.5 mg/mL
- How
- Applied to the ulcer
- How often
- Twice a week
- How long
- 4 weeks in the trial
- This was put on leg ulcers, not injected. No injected dose has been established.
- Other groups got 1.6 or 3.2 mg/mL; the 3.2 mg/mL group healed no better than placebo.
- The 0.5 mg/mL strength showed the largest effect on healing speed.
- A small melanoma study injected 250 or 500 mcg into each tumor once a week for up to 8 weeks (results posted on ClinicalTrials.gov, NCT02225366).
Phase 2b trial
Phase 2b trial (HEAL LL-37) in adults with hard-to-heal venous leg ulcers (Wound Repair and Regeneration, 2021)
Source: Mahlapuu et al., Wound Repair and Regeneration, 2021 (opens in a new tab)
- Weeks 1–13
- 0.5 mg/mL
- How
- Applied to the ulcer
- How often
- Twice a week (every 3 days, give or take a day)
- How long
- 13 weeks in the trial
- This was put on leg ulcers, not injected. No injected dose has been established.
- Another group got 1.6 mg/mL.
- The solution was spread at 25 microliters per square centimeter of ulcer, at routine dressing changes.
- Overall, neither strength healed ulcers better than placebo.
These doses were tested in clinical trials under medical supervision. They aren’t approved for use, and a research vial is not the product that was tested.
Community protocols. Reported online. Not clinically validated.
Community reports Collection date: 30 Sep 2026Most commonly 50–100 mcg (some up to about 125 mcg, or 100 mcg twice a day) injected under the skin once a day for 2–6 weeks, for gut, sinus, Lyme, mold or ‘biofilm’ infections, often alongside thymosin alpha-1.
More about this
Doses vary more than 20-fold: handbooks and vendor templates go to 200–400 mcg a day, a telehealth seller lists 100–1,000 mcg 3–5 times a week, and a 2019 monograph’s 50 mcg per kg a day is far above forum practice.
Daily low dose (antimicrobial / ‘biofilm’)
Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.
- Forum: Reddit r/Peptides, ‘ll-37 dose check’ (comment)
- Forum: Reddit r/Peptides, ‘ll-37 dose check’ (comment)
- Clinic: Hatter Labs (telehealth clinic), LL-37 Protocol Guide
- Practitioner: Ben Greenfield, ‘Ben’s Peptide Stack’ article (immunity stack)
Frequency labels describe this collection, not a measured population. Contradictory records remain available.
Details and sourcesHide details
- Dose
- 50–100 mcg (some about 125 mcg; Ben Greenfield lists 100 mcg twice a day)
- How often
- Once a day (some twice a day)
- Route
- Injection under the skin, in the belly or near a local infection
- Timing
- Morning (Hatter Labs)
- How long
- 2–6 weeks
- Cycle
- Hatter Labs: 2 weeks on, at least 4 weeks off; or 4 weeks on, 6–8 weeks off
- Ramp
- Start low; users stress that ‘less is more’
- Mixing
- 5 mg research vial + 2–3 mL bacteriostatic water (about 1.7–2.5 mg per mL; 100 mcg is about 4–6 units)
- Often stacked with thymosin alpha-1, for example LL-37 50–100 mcg daily for 2–4 weeks plus thymosin alpha-1 1.6 mg 2–3 times a week (Hatter Labs); Reddit users call LL-37 plus thymosin alpha-1 (TA1) ‘the protocol’ for mold or parasites.
- Clinics often add vitamin D, because the body’s own LL-37 depends on it.
- Uncited SEO pages repeat ‘125 mcg daily for 50 days, then 4 weeks off’; no primary source was found.
Sources (4)
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ForumReddit r/Peptides, ‘ll-37 dose check’ (comment) (opens in a new tab)
“This is higher than what I’ve seen quoted on this forum, which is usually 50-100mcg daily.”
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ForumReddit r/Peptides, ‘ll-37 dose check’ (comment) (opens in a new tab)
“The dose is 50mcg/day. That’s all you need.”
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ClinicHatter Labs (telehealth clinic), LL-37 Protocol Guide (opens in a new tab)
“Typical protocol: LL-37 50-100 mcg daily for 2-4 weeks + Ta1 1.6 mg 2-3x/week for 8 weeks”
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PractitionerBen Greenfield, ‘Ben’s Peptide Stack’ article (immunity stack) (opens in a new tab)
“100mcg 2x/day for 4–6 weeks”
Longer titrated daily course
Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.
- Forum: Reddit r/Peptides, ‘ll-37 dose check’ (comment quoting the IPS Peptide Handbook)
- Vendor: PeptideDosages.com, LL-37 5 mg vial protocol
Frequency labels describe this collection, not a measured population. Contradictory records remain available.
Details and sourcesHide details
- Dose
- 200–400 mcg a day (built up from 50 mcg)
- How often
- Once a day (optional 5 days on, 2 days off)
- Route
- Injection under the skin
- How long
- 6–12 weeks (vendor template: optional extension to 16 weeks)
- Ramp
- Vendor template: 50 mcg a day in week 1, adding 50 mcg each week to 400 mcg in week 8
- Mixing
- 5 mg vial + 3 mL bacteriostatic water (about 1.67 mg per mL; 100 mcg is 6 units)
- A Reddit user reports that the International Peptide Society’s 2023 ‘Peptide Handbook’ lists 200 mcg daily for 6–8 weeks, plus vitamin D if blood levels are low.
Sources (2)
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“The general dosage for LL-37 in that book (p72) is 200mcg daily for 6-8 weeks.”
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VendorPeptideDosages.com, LL-37 5 mg vial protocol (opens in a new tab)
“LL-37 is dosed at 50 mcg–400 mcg daily via subcutaneous injection in educational protocols.”
Show all 7 protocolsShow fewer protocols
Three to five times a week, higher doses
Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.
- Vendor: AgeREcode LL-37 Clinical Protocol Guide (supplier guide for physicians)
- Vendor: FormBlends (telehealth seller), LL 37 Dosage Protocols
Frequency labels describe this collection, not a measured population. Contradictory records remain available.
Details and sourcesHide details
- Dose
- 100–800 mcg per shot (one seller: up to 1,000 mcg); into a muscle 300–1,000 mcg
- How often
- 3 times a week (3–5 times a week for ‘aggressive anti-biofilm’ use); muscle shots 1–2 times a week
- Route
- Injection under the skin; sometimes into a muscle
- How long
- 4–12 weeks; the highest dose only as a short 4–6 week course
- Cycle
- Maintenance 1–2 times a week as needed (AgeREcode)
- Ramp
- Start at 100–250 mcg for 1–2 weeks, then step up by 100–250 mcg every few days (FormBlends)
- From a peptide supplier’s guide for physicians (AgeREcode, hosted by Gratia Medical) and a telehealth seller (FormBlends).
Sources (2)
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VendorAgeREcode LL-37 Clinical Protocol Guide (supplier guide for physicians) (opens in a new tab)
“100–300 mcg SC, 3× weekly”
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VendorFormBlends (telehealth seller), LL 37 Dosage Protocols (opens in a new tab)
“Reference dosing for subcutaneous LL 37 in chronic infection adjunct contexts runs 100 to 1,000 mcg per administration, delivered 3 to 5 times per week.”
Nasal spray (chronic sinusitis, nasal MARCoNS in mold illness)
Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.
- Forum: Reddit r/Peptides, ‘How should i dissolve my LL-37 for using it as a nose spray?’ (post)
- Vendor: AgeREcode LL-37 Clinical Protocol Guide (intranasal section)
- Vendor: FormBlends (telehealth seller), LL 37 Dosage Protocols
Frequency labels describe this collection, not a measured population. Contradictory records remain available.
Details and sourcesHide details
- Dose
- 30–100 mcg per dose or per nostril (one seller: 100–500 mcg per spray)
- How often
- Once or twice a day
- Route
- Nasal spray
- How long
- 2–4 weeks (AgeREcode)
- Mixing
- Users dissolve research-vial powder in saline for a spray bottle
- Some mold-illness (CIRS) patients plan homemade sprays that mix LL-37 with KPV to clear nasal staph (MARCoNS).
- Sellers mention nasal burning as a side effect.
Sources (3)
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“I’d like to use it for 30-50 µg dose daily.”
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VendorAgeREcode LL-37 Clinical Protocol Guide (intranasal section) (opens in a new tab)
“50–100 mcg per nostril”
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VendorFormBlends (telehealth seller), LL 37 Dosage Protocols (opens in a new tab)
“Delivered as a spray, usually 100 to 500 mcg per actuation, once or twice daily.”
Nebulized (lung infections)
Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.
- Vendor: AgeREcode LL-37 Clinical Protocol Guide (nebulized section)
- Vendor: FormBlends (telehealth seller), LL 37 Dosage Protocols
Frequency labels describe this collection, not a measured population. Contradictory records remain available.
Details and sourcesHide details
- Dose
- 50–100 mcg (AgeREcode) up to 500–2,000 mcg (FormBlends) per treatment
- How often
- Once a day to several times a week
- Route
- Inhaled from a nebulizer
- The two sellers disagree about 20-fold. Both call it specialist-only because of airway irritation.
Sources (2)
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VendorAgeREcode LL-37 Clinical Protocol Guide (nebulized section) (opens in a new tab)
“50–100 mcg in saline”
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VendorFormBlends (telehealth seller), LL 37 Dosage Protocols (opens in a new tab)
“Reference dosing delivers 500 to 2,000 mcg per nebulization treatment, anywhere from daily to several times weekly.”
Weight-based dose from a 2019 monograph
Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.
- Practitioner: LL-37 Medical Professional Monograph (hosted by Northampton Integrative Medicine, 2019)
- Forum: Reddit r/Peptides, ‘ll-37 dose check’ (post)
Frequency labels describe this collection, not a measured population. Contradictory records remain available.
Details and sourcesHide details
- Dose
- 50 mcg per kg of body weight (about 3.5–4.5 mg for most adults)
- How often
- Once a day
- Route
- Injection under the skin
- From a ‘Medical Professional Monograph’ hosted by an integrative clinic. When a user worked it out to 4.5 mg (a whole 5 mg vial) a day, forum members said it was far too high.
Sources (2)
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PractitionerLL-37 Medical Professional Monograph (hosted by Northampton Integrative Medicine, 2019) (opens in a new tab)
“50 mcg/kg SubQ daily”
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ForumReddit r/Peptides, ‘ll-37 dose check’ (post) (opens in a new tab)
“dose is 50mcg/kg per day subq - I weigh 90kg so my dose is (50mcg x 90 = 4500mcg = 4.5mg)”
Short burst during an acute infection
Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.
- Forum: Reddit r/Peptides, ‘LL-37 cumulative overdose’ (post)
- Forum: Reddit r/Peptides, ‘LL-37 first day side effects’ (comment)
Frequency labels describe this collection, not a measured population. Contradictory records remain available.
Details and sourcesHide details
- Dose
- 200–400 mcg a day, or a single 250 mcg shot
- How often
- Once a day for a few days, or once
- Route
- Injection under the skin
- How long
- About 5 days
- Usually stacked with BPC-157, TB-500 or GHK-Cu. The user fighting flu had a strong reaction after a larger final dose (see cautions).
Sources (2)
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ForumReddit r/Peptides, ‘LL-37 cumulative overdose’ (post) (opens in a new tab)
“200 - 400 µg LL-37”
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ForumReddit r/Peptides, ‘LL-37 first day side effects’ (comment) (opens in a new tab)
“Just 1 shot of very low dose of LL-37 (250 mcg) cure the pain within hours.”
Where the numbers come from
No human injection studies exist; human trials have been topical (leg ulcers), and FDA says it lacks enough safety information to know whether LL-37 harms people. The numbers come from practitioner materials, not trials: a 2019 professional monograph (50 mcg per kg a day), the International Peptide Society’s Peptide Handbook (200 mcg a day for 6–8 weeks, as reported on Reddit), and Lyme, mold and ‘biofilm’ clinics and biohackers (Ben Greenfield’s 100 mcg twice a day for 4–6 weeks). Forum practice settled lower, at 50–100 mcg a day, often paired with thymosin alpha-1.
Home-made sprays and serums
On the skin: home-made serums. Community recipes. Not tested.
Original source recordsHide
LL-37 has been tested as a topical treatment for hard-to-heal venous leg ulcers in two clinical trials. No home-made or cosmetic recipes were found.
Best evidence: Two randomised placebo-controlled trials. In the first (34 patients), LL-37 at 0.5, 1.6 or 3.2 mg per mL was applied twice a week for 4 weeks; the two lower strengths improved healing, the highest did not. The larger phase 2b trial (148 patients) at 0.5 or 1.6 mg per mL found no significant improvement overall. The drug is not approved.
Clinical-trial solution for leg ulcers: 0.5, 1.6 or 3.2 mg per mL, twice a week
Original source-specific report. Collection checked 30 Sep 2026; presentation annotated 2026-10-01. Source date and reporter identity are not separately verified. Exact form and route are limited to the source’s description.
- Study: Grönberg A et al., Wound Repair Regen 2014
- Study: Grönberg A et al., Wound Repair Regen 2014
- Study: Mahlapuu M et al., Wound Repair Regen 2021 (phase 2b)
- Study: Grönberg A et al., Wound Repair Regen 2014
Batch: not stated
Ingredients and methodHide the recipe
Ingredients
| Ingredient | Amount | Role |
|---|---|---|
| LL-37 | 0.5, 1.6 or 3.2 mg per mL | Active |
| Vehicle (not described in the abstracts) | Base |
Method
Made by the trial sponsor; not available to buy.
- How it’s used
- Applied to the ulcer twice a week for 4 weeks, with compression therapy.
- The 2014 trial reported no local or systemic safety concerns.
Sources (4)
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StudyGrönberg A et al., Wound Repair Regen 2014 (opens in a new tab)
“twice weekly applications of LL-37 (0.5, 1.6, or 3.2 mg/mL) or placebo”
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StudyGrönberg A et al., Wound Repair Regen 2014 (opens in a new tab)
“No difference in healing was observed between the groups receiving 3.2 mg/mL of LL-37 and placebo.”
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StudyMahlapuu M et al., Wound Repair Regen 2021 (phase 2b) (opens in a new tab)
“did not identify any significant improvement in healing in patients treated with LL-37 as compared with the placebo.”
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StudyGrönberg A et al., Wound Repair Regen 2014 (opens in a new tab)
“There were no safety concerns regarding local or systemic adverse events.”
How the method was put together, step by step with its sources
Editorial synthesis and reported strength comparison
This synthesized method combines source records. It has not been validated for preparation, sterility, compatibility, absorption or storage. Select a reported strength to inspect the arithmetic; no strength is selected for you.
No amounts were found in the reviewed recipe records for this one. What was found is under “Original source records”.
The general method for home-made serums, with its sources
Good to know
- Use distilled water, not tap: tap water carries minerals, chlorine and microbes that can spoil the serum.
What people report
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Regulator
The FDA says nonclinical research suggests LL-37 may harm male reproduction and may promote tumours in some tissues.
Research notes
1) Doses disagree by more than 20-fold: forum 50–100 mcg a day, handbook 200 mcg a day, vendor templates up to 400 mcg a day, a telehealth seller 100–1,000 mcg 3–5 times a week (and 500–2,000 mcg nebulized), and a 2019 monograph 50 mcg per kg a day (about 3.5–4.5 mg). 2) Regulatory status: FDA’s April 2026 safety page lists LL-37 as a withdrawn nomination with safety concerns, and it is in no 503A category (FDA list updated May 14, 2026). FDA has scheduled its compounding advisory committee to discuss LL-37 for the 503A bulks list before the end of February 2027 (page current April 15, 2026). Some telehealth sellers (for example FormBlends) already advertise 503A-compounded LL-37. 3) The widely repeated ‘125 mcg daily for 50 days, then 4 weeks off’ appears only on uncited SEO pages; no origin found. 4) FormBlends’ article reads as marketing copy (an unverified pharmacist anecdote). 5) Users report reactive arthritis and inflammatory flares, consistent with studies linking LL-37 to psoriasis and rosacea; some clinics say not to use it with rosacea, psoriasis or lupus. 6) Fringe uses seen on Reddit include vaginal use mixed into probiotic gel for bacterial vaginosis (no dose given).
On the skin
No community or cosmetic topical use found; the only topical data are the leg-ulcer trials. General web search engines were largely blocked during this research (captcha / degraded results), so a web-only product could have been missed.
What it is. In plain English.
A human antimicrobial host-defense peptide studied in wound and infection research.
TapClick a dotted word to see what it means.
A 37-amino-acid peptide (starting with two leucines, hence “LL”) cut from a larger protein called hCAP18. White blood cells and skin cells release it.
It punctures bacterial membranes, breaks up biofilms, neutralizes and recruits immune cells. It also influences wound healing and .
Reviewed 2026-10-01.
Structure. What it really looks like.
Experimental
LL-37 (violet) on its own, measured in a crystal. No receptor or other partner protein is part of this structure.
Missing parts
- The last three of its 37 amino acids have no coordinates.
5NMN, Sancho-Vaello et al., 2017. Rendered with Mol* (Sehnal et al., 2021) from RCSB PDB data (Berman et al., 2000).
Specs. The facts at a glance.
- Length
- 37 amino acids
- Sold as
- LL-37 10 mg
- Regulatory status
- Not approved. Investigational.
- Also known as
- Human cathelicidin
Sources. What this page rests on.
Every source behind this page, with what it says and when it was checked, is in the Source library.
Original overview and research notes · annotated 2026-10-01
Historical collection text. Read alongside the claim corrections above; identity or evidence qualifications may supersede this wording.
Natural antimicrobial defense
Your immune system’s own antimicrobial peptide.
A 37-amino-acid peptide (starting with two leucines, hence “LL”) cut from a larger protein called hCAP18. White blood cells and skin cells release it.
It punctures bacterial membranes, breaks up biofilms, neutralizes endotoxin and recruits immune cells. It also influences wound healing and blood-vessel growth.
A small trial of topical LL-37 on chronic venous leg ulcers showed faster healing. It’s studied as a template for new antibiotics. Excess LL-37 is linked to psoriasis, rosacea and lupus flares.
Original status record: Not approved. Investigational.