LL-37
Your body's own antimicrobial peptide, for stubborn wounds, chronic infections and biofilm. Start at 50 mcg; more is not better here.
What it is
LL-37 is for the person with an infection that will not clear (a wound that has stalled for months, recurring sinus or gut infections, a suspected biofilm) who has already done the antibiotic rounds. It is the antimicrobial peptide your own immune cells make, and the one solid human finding is that a low dose beat a high one.
The people who run it have a chronic problem a normal course of antibiotics did not finish: a leg or foot ulcer that has not closed, recurring infections that keep coming back, Lyme or mold protocols where a biofilm is suspected, or a gut that stays inflamed after an infection. It is not a recovery peptide for a sore tendon (BPC-157 is), and it is not something to take instead of antibiotics for an acute infection with a fever.
What you notice depends on what you are treating. For a stalled wound the first sign is the edges tightening and the base looking pinker within two to three weeks; the human trial measured faster closure over a month. For chronic infection or biofilm the feel is less direct: some people get a short flare in the first week (fatigue, achiness, looser stools) as bacterial load shifts, then feel steadily better across weeks four to eight. If you feel nothing at all by week six at 100 mcg, it is probably not addressing your problem. It will not replace a proper diagnosis of what the infection actually is.
Start at 50 mcg once a day subQ for the first one to two weeks, move to 100 mcg as the standard, and go above that only if 100 mcg has done nothing after four weeks; 400 mcg is the ceiling. The reason to ramp is that some people get histamine-type reactions (flushing, itchy injection sites) and the human wound data showed the lowest concentration outperforming the highest, so there is no prize for speed. Inject near a wound if you can reach it, otherwise the belly. A 5 mg vial is 50 doses at 100 mcg, about seven weeks, so an 8 to 12 week run takes two vials; even so it is one of the cheaper peptides per cycle. Run it 8 to 12 weeks for the job at hand, then stop for a few weeks before any further run. The break is not because it wears off: LL-37 turns the immune system up, and too much of it is tied to flares of psoriasis and rosacea. The common mistake is treating it like BPC and going to the top of the range in week one.
The human evidence is a randomized trial of topical LL-37 on hard-to-heal venous leg ulcers, where the 0.5 and 1.6 mg/ml strengths healed faster than placebo and the 3.2 mg/ml strength did not, plus a follow-up trial in the same setting. Everything about injecting it for systemic infection or biofilm comes from cell and animal work (it kills a broad range of bacteria, neutralizes endotoxin, and modulates immune cells) and from clinic experience. So: real human data for wounds, mechanism plus anecdote for everything else, and not approved anywhere.
If the problem is a tendon, a joint or a muscle, BPC-157 or BPC-157 + TB-500. If it is gut inflammation without a clear infectious driver, KPV is cheaper and more targeted. If you have an autoimmune disease, especially lupus, psoriasis or rheumatoid arthritis, LL-37 is one to skip: it is implicated in flares of exactly those conditions, and the risk is not worth a speculative benefit.
What people use it for
Stalled wounds and ulcers
Some evidenceA randomized trial of topical LL-37 on venous leg ulcers that had not healed for months found faster healing than placebo at the two lower concentrations, and no benefit at the highest. A follow-up trial in the same setting continued the work. That is proper human data, and it says two things: it works on stubborn wounds, and more is not better.
Chronic infections and biofilm
Early daysIn the lab LL-37 punches holes in bacterial membranes, breaks up biofilm and neutralizes endotoxin across a broad range of bacteria and some fungi. In animal infection models it reduced bacterial load. Injecting it for a chronic infection in a person is mechanism plus clinic experience, not trial data.
Immune balance
Early daysLL-37 is part of how your own immune system responds to infection, recruiting immune cells and shaping inflammation. The same action is why it is implicated in autoimmune flares (lupus, psoriasis). For most people it is a modest immune nudge; for anyone with an autoimmune diagnosis it is a reason to skip it.
How people use it
Safety, in brief
Things people sometimes notice
- Redness or itch at the injection site, more at higher doses
- A warm flush shortly after a dose
- A short flare of fatigue, achiness or looser stools in the first week when treating a chronic infection
The full picture — stop signs and who should talk to a doctor first — is on the dosing guide.
Sources
The labels and studies behind this page. Each link opens the original on PubMed, DailyMed or ClinicalTrials.gov.
- Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial
- Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: A multicentric prospective randomized placebo-controlled clinical trial
- Human host defense peptide LL-37 prevents bacterial biofilm formation
- Plasmacytoid dendritic cells sense self-DNA coupled with antimicrobial peptide