LL-37: Your Body's Antimicrobial Peptide
LL-37 is a naturally occurring peptide your body produces as part of your immune system's front-line defense. Think of it as a tiny molecular soldier that patrols your skin, lungs, and digestive tract looking for unwanted invaders—bacteria, fungi, and viruses. People are interested in it because it's remarkably versatile and effective where conventional antibiotics sometimes fail.
Here's how it works: bacteria have negatively charged surfaces, kind of like opposite ends of a magnet. LL-37 has a positive charge, so it's naturally attracted to these bacterial cells. When it makes contact, it basically punctures holes in the bacterial membrane, which causes the cell to leak and die. What makes this particularly clever is that it works against almost everything harmful—gram-positive bacteria, gram-negative bacteria, fungi, and even enveloped viruses.
LL-37 also tackles one of modern medicine's trickier problems: bacterial biofilms. These are like organized communities of bacteria that stick together and resist antibiotics. LL-37 prevents bacteria from joining these colonies in the first place and can actually dismantle existing biofilms. Beyond killing invaders, it also reduces inflammation and helps accelerate wound healing by promoting new blood vessel growth. It's essentially your immune system's multitool.
Dosage Information
Typical Dose
50-100 mcg
Frequency
Once daily
Administration
Subcutaneous injection
Half-Life
~4 hours
estimatedNotes
Can be used topically for wound healing or SubQ for systemic immune support. Cycles typically run 4-8 weeks. Particularly useful for chronic infections with biofilm involvement (Lyme, sinusitis, etc.).
Why this matters
Antimicrobial peptide; local tissue concentrations matter more than plasma levels.
Protocol cycle
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Where does LL-37 sit?
See how this peptide compares across all 150 peptides in our database.
Evidence Score
0.69
Compound Data
Molecular Formula
C205H340N60O53
Molecular Weight
4493.00 g/mol
IUPAC Name
(4S)-5-[[(2S)-6-amino-1-[[(2S,3S)-1-[[2-[[(2S)-6-amino-1-[[(2S)-1-[[(2S)-1-[[(2S)-6-amino-1-[[(2S)-1-[[(2S,3S)-1-[[(2S)-1-[[(2S)-5-amino-1-[[(2S)-1-[[(2S,3S)-1-[[(2S)-6-amino-1-[[(2S)-1-[[(2S)-1-[[(2S)-1-[[(2S)-1-[[(2S)-4-amino-1-[[(2S)-1-[[(2S)-1-[(2S)-2-[[(2S)-5-carbamimidamido-1-[[(2S,3R)-1-[[(2S)-4-carboxy-1-[[(1S)-1-carboxy-2-hydroxyethyl]amino]-1-oxobutan-2-yl]amino]-3-hydroxy-1-oxobutan-2-yl]amino]-1-oxopentan-2-yl]carbamoyl]pyrrolidin-1-yl]-3-methyl-1-oxobutan-2-yl]amino]-4-methyl-1-oxopentan-2-yl]amino]-1,4-dioxobutan-2-yl]amino]-5-carbamimidamido-1-oxopentan-2-yl]amino]-4-methyl-1-oxopentan-2-yl]amino]-1-oxo-3-phenylpropan-2-yl]amino]-3-carboxy-1-oxopropan-2-yl]amino]-1-oxohexan-2-yl]amino]-3-methyl-1-oxopentan-2-yl]amino]-5-carbamimidamido-1-oxopentan-2-yl]amino]-1,5-dioxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-3-methyl-1-oxopentan-2-yl]amino]-5-carbamimidamido-1-oxopentan-2-yl]amino]-1-oxohexan-2-yl]amino]-1-oxo-3-phenylpropan-2-yl]amino]-4-carboxy-1-oxobutan-2-yl]amino]-1-oxohexan-2-yl]amino]-2-oxoethyl]amino]-3-methyl-1-oxopentan-2-yl]amino]-1-oxohexan-2-yl]amino]-4-[[(2S)-6-amino-2-[[(2S)-2-[[(2S)-6-amino-2-[[(2S)-2-[[(2S)-2-[[(2S)-2-[[(2S)-2-[[2-[[(2S)-2-[[(2S)-2-amino-4-methylpentanoyl]amino]-4-methylpentanoyl]amino]acetyl]amino]-3-carboxypropanoyl]amino]-3-phenylpropanoyl]amino]-3-phenylpropanoyl]amino]-5-carbamimidamidopentanoyl]amino]hexanoyl]amino]-3-hydroxypropanoyl]amino]hexanoyl]amino]-5-oxopentanoic acid
PubChem CID
16198951Potential Side Effects
LL-37 discussions
Stacking Compatibility
In These Stacks
Quick Facts
- Administration
- Subcutaneous injection
- Typical Dose
- 50-100 mcg
- Frequency
- Once daily
- References
- 2 curated + 44 from PubMed
- Clinical Trials
- 12 registered
- Evidence Score
- 0.7 / 100
Frequently Asked Questions about LL-37
What is LL-37?
LL-37 is the only cathelicidin antimicrobial peptide found in humans. It is a 37-amino acid peptide that serves as a critical component of the innate immune system. Beyond its antimicrobial activity, it modulates inflammation, promotes wound healing, and disrupts bacterial biofilms — persistent bacterial colonies that are resistant to conventional antibiotics.
How does LL-37 work?
LL-37 disrupts bacterial membranes through electrostatic interactions with their negatively charged surfaces, creating pores that lead to cell death. It is active against gram-positive and gram-negative bacteria, fungi, and enveloped viruses. It disrupts biofilms by preventing initial bacterial adhesion and degrading established biofilm structures. It also modulates TLR signaling and promotes angiogenesis during wound repair.
What is the recommended dosage for LL-37?
The typical dose is 50-100 mcg. Once daily. Administration: Subcutaneous injection. Can be used topically for wound healing or SubQ for systemic immune support. Cycles typically run 4-8 weeks. Particularly useful for chronic infections with biofilm involvement (Lyme, sinusitis, etc.).
What are the side effects of LL-37?
Injection site pain. Localized redness. Mild flu-like symptoms. Herxheimer-like reaction
What is the LL-37 cycle protocol?
LL-37 is typically cycled 4-8 weeks. Cycles typically run 4-8 weeks duration
Questions reflect common community inquiries. This is not medical advice.