In plain English
LL-37 is a natural peptide made by your immune cells and skin that kills microbes directly and helps direct the immune response. It is the only member of the cathelicidin family in humans.
What it's used for
- Immune defense against bacteria, viruses and fungi
- Stubborn or recurring infections, including biofilms
- Wound healing
- Gut and immune balance
Benefits
In laboratory and animal studies, LL-37 killed a wide range of microbes, broke down biofilms and sped up wound healing. In a small human study, it improved healing of hard-to-heal leg ulcers. Users report it helps with chronic infections and immune recovery.
How it works
In simple terms: LL-37 punches holes in microbes and calls in immune help.
Its positive charge attracts it to the negatively charged membranes of bacteria and other microbes, which it breaks open. It also neutralizes bacterial toxins, signals immune cells to the area and promotes blood vessel growth and skin repair. Vitamin D increases the body’s own production.
Development history
- 1995: Discovered as the human cathelicidin.
- 2000s: Linked to vitamin D, skin defense and wound healing.
- 2010s: Tested in leg ulcer trials.
Typical protocols
These ranges are what users commonly report.
| Use | Dose | Frequency | Length |
|---|---|---|---|
| Immune support | 100–125 mcg | Daily | 2–6 weeks |
Cycling
Commonly used in courses of 2–6 weeks.
Administration options
Subcutaneous injection.
Reconstitution and dosing calculator
Usually comes in 5 mg vials, mixed with 2–3 mL of bacteriostatic water.
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This tool does arithmetic only. It does not choose a dose or confirm that any substance is right for you. Double-check every result against your syringe and your clinician’s instructions.
Side effects and safety
- Injection-site redness, itching or pain is common.
- Flu-like feelings or a "die-off" reaction can occur when many microbes are killed at once.
- High levels are linked to inflammation in conditions such as psoriasis and rosacea; people with autoimmune disease should be cautious.
- Avoid during pregnancy and breastfeeding.
Common stacks
- Thymosin Alpha-1: for immune support.
- BPC-157 or KPV: for the gut.
Storage
Powder: refrigerate or freeze. After mixing: refrigerate at 2–8 °C and use within about 2–3 weeks.
Compare with
- Thymosin Alpha-1: tunes immune cells rather than killing microbes directly.
- KPV: calms inflammation, with some antimicrobial effects.
Frequently asked questions
Does vitamin D raise LL-37?
Yes. Vitamin D switches on the gene for cathelicidin, which is one reason low vitamin D is linked to more infections.
References
- Dürr UHN, Sudheendra US, Ramamoorthy A. LL-37, the only human member of the cathelicidin family of antimicrobial peptides. Biochim Biophys Acta. 2006;1758(9):1408-1425.
- Grönberg A, et al. Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers. Wound Repair Regen. 2014;22(5):613-621.