LL-37

LL-37 is a natural peptide your own body makes. Your white blood cells and skin use it to fight germs. It is the only human cathelicidin, which is a family of germ-fighting peptides.

It does two jobs. It can punch holes in germs directly. It also sends signals that steer your immune system. It has 37 building blocks, which is fairly large for a peptide.

It is not FDA-approved. It is sold for research only.

People use it for chronic infections. The crowd buying it is often dealing with chronic Lyme, mold illness (CIRS), or hard-to-clear infections that form a slimy layer called a biofilm.

These are contested diagnoses. Contested does not mean fake. But it does mean there is often no clear test to tell you if it is working or when to stop. Keep that in mind.

What exists is two small wound studies and a mountain of lab work that has never been tested in a living person the way people actually use it.

The only real human trials were small. Two studies, about 30 patients each, used LL-37 placed on top of stubborn venous leg ulcers (open sores on the leg). Those showed it helped the wounds heal.

Here is the gap. That proof is for putting it on a wound on your skin. The Lyme and biofilm crowd usually injects it under the skin instead. That route has almost no human data. There are about 800 lab and animal studies, but those do not replace human trials.

The trials that worked used LL-37 placed directly on a skin wound (topical). That readout took about 84 days, or 12 weeks.

Most people in the chronic-infection crowd inject it under the skin instead. That route is basically uncharted in humans, and the right dose is poorly known.

If you run it for infection symptoms, give it a fixed window, say 8 to 12 weeks, and decide up front what "better" would even look like, since there is no lab number to chase here. There is no proven ladder where longer or higher pulls out a win.

The serious stuff

LL-37 is part of your immune system, not just a germ-killer. High local levels are actually seen in some skin diseases. So it can make them flare. - Skip it if you have rosacea, psoriasis, or any lupus-type diagnosis. - Do not run it alongside antibiotics without your doctor steering. LL-37 is itself a germ-fighter, so it can boost both the effect and the toxicity of your antibiotic. - Do not run it alongside immune-suppressing drugs. They work against each other.

There is also deeper science worth reading: LL-37 can bind your own DNA and trigger an immune alarm (interferon-alpha). That is the part we would want anyone to read first.

Talk to a real doctor. We are not your doctor.

Here are the lanes, safest to riskiest.

• Brand. None. No FDA-approved LL-37 exists.
• Compounded. Some pharmacies make it with a prescription, about $140–$300 a month. The trial proof is for the skin, so injecting it is off-label.
• Research-only (RUO). The main source, about $45–$120 a month. LL-37 is long and hard to make cleanly, so weak, sub-90% purity is common.
• Gray market. Overseas raw, around $6 a month spread out. Paid by crypto, no lab report. The hard synthesis means fakes and wrong-identity vials are common at the cheapest tier.

Always ask for a COA, a lab report on what is really in the vial.