LL-37
The human body's own antimicrobial peptide, cut from cathelicidin.
Overview
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.
How it works
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
Compound facts
- Type
- Cationic host-defense (antimicrobial) peptide
- CAS Number
- 154947-66-7
- Molecular Weight
- ~4493 g/mol (C205H340N60O53)
- Amino Acids
- 37
- Sequence
- LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES
- Parent protein
- hCAP-18 (human cathelicidin, CAMP gene)
Reported benefits
Leg-ulcer healing
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.
Antimicrobial and anti-biofilm
Kills many bacteria and fungi and disrupts biofilms in the lab.
Infection defense
Protects against infection in animal models.
Fewer infections, better gut
Users report fewer colds and help with chronic infections. Self-reported only.
“Anecdotal” means reported by users, not shown in controlled trials.
Community-reported regimens
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 |
Reconstitution calculator
Set up for LL-37. Switch peptide or vial size any time.
1Mix
Add 2 mL water for 2.5 mg/mL
2Draw
Draw to 4 units = 0.04 mL = 100 mcg
Drag the plunger to set your dose.
3Inject
Next site
Right belly, upper
Tap a site after you inject to keep a rotation.
Pinch the skin, stay 2 in. from the navel, then into a sharps bin.
- Doses per vial
- 50
- Vial lasts
- 50 days
- Good once mixed
- ~28 days
- Syringe
- 30-unit, 0.3 mL
The vial outlasts its ~28-day shelf life once mixed. A smaller vial wastes less.
Under 5 units is hard to measure accurately. Add more diluent for an easier draw.
Math only: concentration (mg/mL) = vial mg ÷ mL of water; units = dose (mg) ÷ concentration × 100. Always double-check against your own vial label and a clinician. This tool does not recommend a dose.
Reconstitution
Diluent: Bacteriostatic water (0.9% benzyl alcohol) — allows multiple draws from one vial.
- Wipe both vial tops with an alcohol swab and let dry.
- Draw the diluent, then inject it slowly down the inside wall of the vial — never straight onto the powder.
- Swirl gently or let it sit; do not shake. Foam can damage peptides.
- Solution should be clear. Cloudy, stringy or discolored = discard.
- Small doses are easier to measure with more diluent.
- Common mix: 5 mg + 2.5 mL = 2 mg/mL (100 mcg = 5 units).
Storage
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.
Side effects & cautions
Reported side effects
- Injection-site pain, redness or swelling (it can irritate cells at high concentration)
- Flu-like feeling or fatigue
- Itching or rash
- Unknown long-term effects
Cautions
- High LL-37 levels are linked to psoriasis, rosacea and lupus. Avoid with autoimmune disease.
- Lab studies show it can promote some cancers (e.g. ovarian, breast) and suppress others. Avoid with a cancer history.
- No human data for injected use.
- No data in pregnancy or breastfeeding.
FDA & international status
Not FDA-approved
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.
Often paired with
Thymosin Alpha-1A common community immune pairing. No studies of the two together.
Where to buy
| Size | Price | Per mg | Stock | Latest COA |
|---|---|---|---|---|
| 5 mg | $34.99 | $7.00 | In stock | 99.9% pure, lot LL0001 ILS Labs, tested 2026-08-19 |
Amino Club list prices as of 2026-10-07, before promo codes. Multi-buy: 2+ units 5% off, 3+ units 7.5% off, 10+ units 40% off. Prices change; confirm on the product page. Mixing? Their bacteriostatic water is Amino H2O from $19.99.
LL-37 at Amino Club
Check sizes, current price and the certificate of analysis (COA) on the product page. Sold for in-vitro research only.
Get LL-37 alerts
An email when its price drops, a sale starts, or its FDA or WADA status changes.
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- Look for a batch-specific COA with HPLC purity (≥98%) and mass-spec identity.
- Typical vial sizes: 5 mg.
FAQ
Does my body already make LL-37?
Yes. Skin, gut and immune cells make it, and vitamin D raises production. Supplementing vitamin D is the studied way to raise it.
Why does it hurt to inject?
LL-37 disrupts cell membranes, and at high local concentration it can irritate your own tissue. More diluent and rotating sites can help.
Is it an antibiotic replacement?
No. It has never been tested as an injected antibiotic in people. Treat real infections with proven drugs.