Emerging evidence · Grade B
LL-37
LL-37 (Human Cathelicidin Antimicrobial Peptide)
Score
62 / 100
Class
Human cathelicidin (AMP)
Role
Innate immune defense
Status
Investigational
TL;DR
01
The only human cathelicidin antimicrobial peptide — a 37-amino-acid molecule that is a genuine part of your innate immune defense, killing microbes and coordinating wound healing.
02
Its biology is real and important: broad antimicrobial activity, endotoxin neutralization, chemotaxis, and angiogenesis.
03
But as a therapy it is early — there are no established human trials for supplementing LL-37, and its mechanism is a double-edged sword.
04
That double edge matters: too much LL-37 is implicated in autoimmune and inflammatory diseases (psoriasis, lupus) and can promote some cancers.
05
It is not approved and is sold as a research chemical.
Endogenous role
Real / important
host defense, wound healing
Therapeutic trials
Early / none established
for supplementation
Double-edged
Yes
autoimmunity, some cancers
Approval
None
research chemical
Type
37-aa peptide
only human cathelicidin
Part 01 · How it works
Mechanism.
LL-37 is a natural weapon of your immune system — the human body's single cathelicidin. Released by immune cells, it punctures bacteria, neutralizes bacterial toxins, recruits other immune cells, and helps wounds heal. That's genuinely important biology. The problem with using it as a supplement is twofold: there's little human trial evidence that adding it helps anything, and the same peptide, in excess or the wrong context, drives inflammatory and autoimmune diseases (it's a known player in psoriasis and lupus) and can feed certain cancers. It's a powerful, context-dependent molecule, not a simple 'immune booster.'
A built-in antimicrobial weapon and repair signal — but one that, turned up in the wrong place, attacks your own tissues. Not a dial you'd want to crank blindly.
Antimicrobial action
Broad-spectrum membrane-disrupting activity against bacteria; neutralizes LPS endotoxin.
Immunomodulation
Chemotactic, angiogenic, and wound-healing activities bridging innate and adaptive immunity.
Double-edged role
Overexpression/dysregulation implicated in psoriasis, lupus, and pro-tumor effects in some cancers.
Evidence stage
Strong endogenous biology; no established human trials for therapeutic supplementation.
Part 02 · Dosing & administration
How it's taken.
Community-reported · unregulatedValues below reflect commonly reported community protocols for LL-37. These are anecdotal and unregulated — not clinically validated and not a recommendation. Provided for educational purposes only — this is not medical advice and not instructions for self-administration. Consult your healthcare provider before making any health decision.
Standard dose
50-100 mcg
Subcutaneous injection (topical for wounds) · Once daily
Duration
2–4 weeks on, ≥2 weeks off
·
Community protocols span roughly 50–400 mcg/day SC; this page stays at the conservative 50–100 mcg end because no validated human systemic regimen exists.
·
Endogenous LL-37 is tightly, locally regulated and vitamin-D-dependent; exogenous systemic dosing is uncharacterized in humans.
·
Unapproved by any regulator; supplied as a research chemical with no purity or dose guarantee.
Need help with reconstitution?
Use the free peptide calculator for dilution, unit conversion, and injection volume.
Part 03 · Safety
Side effects, rare serious events, who shouldn't.
Common
Human tolerability
No established human supplementation data.
Uncharacterized
Serious · rare
Autoimmune/inflammatory potential
Dysregulated LL-37 is implicated in psoriasis and lupus.
Mechanistic concern
Pro-tumor potential
Promotes progression in some cancers in preclinical work.
Mechanistic concern
Product-quality risk
Research-chemical supply; purity/dose unknown.
Source-dependent
Absolute · do not use
×
Active autoimmune disease (LL-37 is a potent immune activator and may exacerbate autoimmunity)
×
Pregnancy or breastfeeding
×
Children under 18
×
Known hypersensitivity to LL-37 or any component
×
Rosacea or psoriasis (LL-37 is elevated in these conditions and may worsen symptoms)
Relative · discuss first
!
Autoimmune or inflammatory disease (e.g., psoriasis, lupus) — mechanistic concern
!
Active or prior cancer — pro-tumor potential in some contexts
!
Pregnancy or breastfeeding — no data
!
Anyone expecting a proven immune benefit — none is established
Interactions
Immunosuppressants
LL-37 strongly activates innate immunity; may counteract immunosuppressive therapy
Major
Biologic therapies (TNF inhibitors, IL-17 inhibitors)
LL-37 activates inflammatory pathways that biologics aim to suppress; potential for opposing effects
Moderate
Anticoagulants
LL-37 has been shown to affect platelet activation and coagulation pathways
Moderate
Labs to monitor
CBC with Differential
Baseline and monthly
Monitor immune cell counts with antimicrobial peptide use
CMP (Comprehensive Metabolic Panel)
Baseline and every 3 months
Liver and kidney function
CRP / ESR
Baseline and monthly
Track inflammatory markers
Vitamin D, 25-OH
Baseline
Vitamin D regulates LL-37 expression; deficiency reduces endogenous production
Part 04 · Evidence
How strong is the evidence?
62
Grade B
Grade B, Emerging. LL-37 is a real, important immune peptide with well-characterized biology, but therapeutic use is early with no established human trials, and its double-edged (pro-autoimmune, pro-tumor) potential is a genuine caution.
Mechanistic plausibility
Well-characterized endogenous antimicrobial/immunomodulatory peptide.
80
Human evidence
Rich basic biology, but no established human therapeutic trials for supplementation.
42
Safety & tolerability
Double-edged: linked to autoimmune/inflammatory disease and some cancers; supplementation safety unknown.
50
Durability
No human outcome data.
50
Independence
Extensively studied across independent labs (as biology, not as a therapy).
66
Part 05 · Research log
Every study we cite.
We list each study with its methodology, funding source, and our quality grade. Flagged studies aren't dismissed — they're tagged so you can weigh them.
01
2008
Front Biosci Flagged
The role of the multifunctional peptide LL-37 in host defense (review)
Summarizes LL-37's antimicrobial, endotoxin-neutralizing, chemotactic, angiogenic, and wound-healing roles as a mediator between innate and adaptive immunity.
Narrative review · Characterizes endogenous biology; not evidence for therapeutic supplementation.
PMID 18508470 ↗
Moderate (review)
Evidence against
What didn't work, and where the evidence is thin.
Every publication is incentivized to tell you a peptide works. We catalogue the null results, failed trials, and mechanism limits we found in the same literature — so you can weigh them against the upside, with your provider.
01
Important biology, but a double-edged therapeutic with no established trials
Safety signal Front Biosci · 2008
LL-37 is a genuine immune-defense peptide, but there are no established human trials for supplementing it — and dysregulated LL-37 is implicated in autoimmune/inflammatory diseases (psoriasis, lupus) and pro-tumor effects in some cancers.
What this means: More is not obviously better with LL-37. Supplementing a context-dependent, potentially pro-autoimmune/pro-tumor peptide without evidence is a real risk, not a simple immune boost.
PMID 18508470 ↗
Part 06 · Cost & access
Where it's available, at what price.
United States
Not approved
No approved product; research chemical.
Grey-market; unregulated
European Union
Not approved
No approved product.
N/A
United Kingdom
Not approved
No approved product.
N/A
Canada
Not approved
No approved product.
N/A
The Peptide Column takes no affiliate commission from any source. LL-37 is an important natural immune peptide but has no established therapeutic trials and a double-edged (pro-autoimmune/pro-tumor) profile; consumer supply is research-grade and unregulated. We link only to clinician-directed care, never to sellers.
Part 07 · Your appointment
Questions to bring.
01
Is LL-37 appropriate for my specific infection or immune condition?
02
What is the delivery method — injectable, topical, or nasal?
03
How does LL-37 compare to conventional antibiotics for my situation?
04
Are there any autoimmune concerns with using an immune-stimulating peptide?
05
What is the evidence level for LL-37 in humans versus animal models?
06
Could LL-37 worsen inflammatory conditions like rosacea or psoriasis?
References
Every citation, numbered.
Citation list. For our editorial read of each study — including bias flags and quality grades — see the Research log above.
- 01. The role of the multifunctional peptide LL-37 in host defense (review) · Front Biosci, 2008 · PMID 18508470 ↗
- 02. PubMed. LL-37 host-defense and disease-association literature