LL-37
Also known as: Cathelicidin antimicrobial peptide, hCAP18 fragment
Quick summary
LL-37 is the only cathelicidin antimicrobial peptide made by humans. Research focus: antimicrobial activity, neutrophil extracellular traps and innate immune modulation. This page leads with SRP's low-and-slow starting dose.
Amino acid sequence (one-letter code): LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES
Overview
LL-37 is the only cathelicidin antimicrobial peptide made by humans. It is a 37-residue helix that disrupts microbial membranes. It also influences immune cell behavior, including neutrophil extracellular trap formation.
Looking for research material? Simple Research Peptides lists LL-37 10 mg Antimicrobial Research Peptide Vial for laboratory research use.
Mechanism
The only human cathelicidin. It is an amphipathic helical peptide that disrupts microbial membranes and also signals to immune cells.
Research areas
- antimicrobial activity
- neutrophil extracellular traps
- innate immune modulation
- sepsis models
Storage & reconstitution
Supplied as a lyophilized powder; keep sealed, dry and away from light, ideally frozen or refrigerated for long-term holding. Laboratories typically reconstitute with bacteriostatic or sterile water, swirling gently rather than shaking, then hold the solution refrigerated (2–8 °C) and use it within the window set by their own stability protocol.
Recommended starting dose (low and slow)
| Starting dose | Low end of the studied range: 50 mcg; 50 mcg; 500 mcg. |
|---|---|
| Frequency | Reported schedules: daily; 50–400mcg daily; Daily. |
| Reconstitution | Examples: 5 mg vial + 2.5 mL bacteriostatic water = 2 mg/mL; 5mg vial + 3mL diluent (as listed). Different water volumes can be used; that only changes the draw volume, not the amount of peptide. storage note: Reconstituted: refrigerate, used within 4 weeks. |
Studied higher doses
Studies have used doses up to the amounts below. Higher doses can be dangerous. Whether a person can reach them safely depends on height, weight, activity level, training and pre-existing conditions. We recommend following the lower starting dose above, and contacting SRP with any questions.
| Highest amount reported in studies | Top of the studied range: 100 mcg; 400 mcg; 1 mg. These are range tops, not verified ceilings. Reported amounts vary by 2x or more. |
|---|
Route and timing
Route: Subcutaneous injection after reconstitution is the route most often described in research protocols.
Timing: Pending - to be added by SRP
Cycle length and repeat
Pending - to be added by SRP
Half-life
Approximate, for Bobby's review: Not well characterized in published research.
Side effects
Pending - to be added by SRP
Suggested bloodwork and monitoring
Draft, for Bobby's review: CBC and comprehensive metabolic panel (kidney and liver function, electrolytes) before starting and again after a few weeks, with a white-cell differential.
Cautions
Pending - to be added by SRP
Reconstitution calculator
Math aid only. It converts the numbers you enter; it is not dosing advice. For research use only. Prefilled with this page's vial size, reconstitution and low-and-slow starting dose where known; change any value.
Frequently asked questions
What is LL-37 studied for?
In research it is studied for antimicrobial activity, neutrophil extracellular traps and innate immune modulation. The only human cathelicidin.
How is LL-37 given in research?
Subcutaneous injection after reconstitution is the route most often described in research protocols. See the dosing frequency block on this page for how often.
What amount should a researcher start with?
This page lists SRP's low-and-slow starting dose in the Recommended starting dose section. Higher amounts that appear in studies are listed separately with their safety context. Start with the lower dose and contact SRP with any questions.
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Last updated: October 19, 2026