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The human body's own antimicrobial peptide, cut from cathelicidin.
Last reviewed Oct 7, 2026 · How we rate evidence · Report an error
LL-37, 37 amino acids, ~4493 g/mol (C205H340N60O53).
LL-37 is the only cathelicidin antimicrobial peptide humans make. It kills bacteria, fungi and some viruses in the lab and helps direct the immune response. A topical form was tested in leg-ulcer trials with mixed results. Injected use is not studied in humans.
A positively charged peptide that disrupts microbe membranes and breaks up biofilms. It also signals immune cells and supports wound closure. The same immune-activating effect is linked to psoriasis, rosacea and lupus when it is overactive.
Evidence
3/5
Small human trials of topical LL-37 for venous leg ulcers; a larger Phase IIb missed its overall goal. No human data for injection.
Half-life
Not established in humans; broken down quickly by proteases
Known as
Cathelicidin, hCAP-18 fragment, Ropocamptide
Compare LL-37 with: Thymosin Alpha-1KPVVIPor any other →
Some human dataSmall or older human trials, or bigger trials with mixed or negative results.
Small human trials of topical LL-37 for venous leg ulcers; a larger Phase IIb missed its overall goal. No human data for injection. How we rate evidence
A small placebo-controlled trial of topical LL-37 sped healing. A larger Phase IIb missed its main goal, with benefit mainly in large wounds.
Kills many bacteria and fungi and disrupts biofilms in the lab.
Protects against infection in animal models.
Users report fewer colds and help with chronic infections. Self-reported only.
“Anecdotal” means reported by users, not shown in controlled trials. Sources
Not recommendations. These are commonly cited ranges, shown so you can see what real-world use looks like.
| Plan | Dose | Frequency | Duration | Route |
|---|---|---|---|---|
| Community standard Community range is roughly 50–125 mcg. | 100 mcg | Once daily | 4–6 weeks | Subcutaneous |
| Community cautious start Injection-site reactions are common; start low. | 50 mcg | Once daily | 1–2 weeks, then reassess | Subcutaneous |
Set up for LL-37. Switch vial size any time. Educational math only, not dosing advice.
At a common mix of 5 mg of LL-37 in 2.5 mL of water (2 mg/mL), these commonly reported doses come to the following on a U-100 insulin syringe (100 units = 1 mL). They are examples of the arithmetic, not recommendations.
| Reported plan | Dose | Draw to | Volume |
|---|---|---|---|
| Community standard | 100 mcg | 5 units | 0.05 mL |
| Community cautious start Under 5 units is hard to measure accurately. Add more diluent for an easier draw. | 50 mcg | 2.5 units | 0.025 mL |
Concentration (mg/mL) = vial mg ÷ mL of water; units = dose (mg) ÷ concentration × 100. A different vial size or amount of water changes every number above.
Amino Club sells LL-37 as a research chemical. Its listings are research-use-only and not for human use; we show them for price tracking and their published lab reports.
Research-use-only listing — not for human use.
40% off through our link (code MYPEPSINFO applies automatically), until Dec 31, 2026.
| Size | Price | Per mg | Stock | Latest COA |
|---|---|---|---|---|
| 5 mg | $20.99 | $4.20 | In stock | 99.68% pure, lot LL0002 ILS Labs, tested Oct 22, 2026 |
List price, checked daily since Oct 7.
| Oct 7, 2026 | $34.99 | |
| Oct 8, 2026 | $34.99 | |
| Oct 9, 2026 | $34.99 | |
| Oct 10, 2026 | $34.99 | |
| Oct 11, 2026 | $34.99 | |
| Oct 12, 2026 | $34.99 | |
| Oct 13, 2026 | $34.99 | |
| Oct 14, 2026 | $34.99 | |
| Oct 15, 2026 | $34.99 | |
| Oct 16, 2026 | $34.99 | |
| Oct 17, 2026 | $34.99 | |
| Oct 18, 2026 | $34.99 | |
| Oct 19, 2026 | $34.99 | |
| Oct 20, 2026 | $34.99 | |
| Oct 21, 2026 | $34.99 | |
| Oct 22, 2026 | $34.99 | |
| Oct 23, 2026 | $34.99 | |
| Oct 24, 2026 | $34.99 | |
| Oct 25, 2026 | $34.99 | |
| Oct 26, 2026 | $34.99 | |
| Oct 27, 2026 | $34.99 | |
| Oct 28, 2026 | $34.99 | |
| Oct 29, 2026 | $34.99 | |
| Oct 30, 2026 | $34.99 | |
| Oct 31, 2026 | $34.99 | |
| Nov 1, 2026 | $34.99 |
HPLC purity from each published lab report; lowest 99.68%.
| Aug 19, 2026 | 99.90% | lot LL0001 |
| Oct 22, 2026 | 99.68% | lot LL0002 |
Amino Club list prices as of Nov 1, 2026; sale prices include the 40% applied through our link. Multi-buy: 2+ units 5% off, 3+ units 7.5% off, 10+ units 40% off. Prices change; confirm on the listing.
An email when it’s back in stock, its price drops, a sale starts, or its FDA or WADA status changes.
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All LL-37 lab reports, lot by lot →
Diluent: Bacteriostatic water (0.9% benzyl alcohol) — allows multiple draws from one vial.
Amazon affiliate links. Disclosure
Powder
Freezer / fridge
Keep sealed vial in the freezer (−20 °C) for long-term storage; fridge (2–8 °C) is fine for a few weeks. Keep dry and out of light.
After mixing
~28 days
Refrigerate at 2–8 °C. Never freeze after mixing. Keep upright, capped, and out of light.
Travel
Keep cool
Short trips at room temperature are generally fine for powder; keep mixed vials cold.
Not an approved drug. It was in FDA compounding Category 2 until April 2026, when its nomination was withdrawn. Removal from that list is not approval. Check the FDA 503A categories page for its current status.
Regulations change often — verify with the FDA, EMA, MHRA, Health Canada, TGA and WADA before acting.
Yes. Skin, gut and immune cells make it, and vitamin D raises production. Supplementing vitamin D is the studied way to raise it.
LL-37 disrupts cell membranes, and at high local concentration it can irritate your own tissue. More diluent and rotating sites can help.
No. It has never been tested as an injected antibiotic in people. Treat real infections with proven drugs.
It depends on the mix. At a common mix of 5 mg of LL-37 in 2.5 mL of water (2 mg/mL), 100 mcg is 5 units (0.05 mL) on a U-100 insulin syringe. The formula is dose in mg ÷ concentration in mg/mL × 100. Change the vial size or water in the calculator and the units update. This is math, not a dose recommendation.
Bacteriostatic water (0.9% benzyl alcohol) — allows multiple draws from one vial. A common mix is 5 mg + 2.5 mL, which gives 2 mg/mL. Less water makes a stronger mix and fewer units per dose; more water makes a weaker mix and more units. Pick the amount that lands your dose on an easy-to-read line.
Refrigerate at 2–8 °C. Never freeze after mixing. Keep upright, capped, and out of light. Plan on about 28 days once it is mixed, and discard it sooner if it turns cloudy or has particles. The calculator shows how long a vial lasts at your dose and flags a vial that outlasts its shelf life.
Evidence rating (3/5): Small human trials of topical LL-37 for venous leg ulcers; a larger Phase IIb missed its overall goal. No human data for injection.
Legal status: Not an approved drug. It was in FDA compounding Category 2 until April 2026, when its nomination was withdrawn. Removal from that list is not approval. Check the FDA 503A categories page for its current status.
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