LL-37
A synthetic copy of the body's own cathelicidin defense peptide. People run it for immune support, for stubborn biofilms and gut issues, and for wound and skin recovery, sometimes alongside BPC-157 or KPV.
Where to buy LL-37, cheapest first.
Prices from 4 vendors across the market. We link straight to each vendor’s product page and grade vendors on public lab data, so you’re not just chasing the lowest number.
LL-37
What LL-37 actually does.
The simple version first, then a little more for the curious. No biochem degree required.
It acts like your body's own first-responder against microbes, punching holes in bacterial membranes and calming the inflammation around an infection, while nudging tissue to repair.
How it works
LL-37 is a cationic, positively charged peptide. It is drawn to the negatively charged surfaces of bacteria, where it disrupts and punctures their membranes. It also binds and neutralizes bacterial endotoxin (LPS), which is part of how it calms infection-driven inflammation.
Where it acts
It is studied for breaking up biofilms, the slimy bacterial communities that resist normal antibiotics, and for host defense at the skin, gut, and airway surfaces where the body naturally makes it. People reach for it with chronic gut or sinus complaints in mind.
What people notice
Reports center on immune support and gut comfort rather than a single dramatic effect. Some describe better wound and skin recovery. Effects, when present, tend to build over a short cycle rather than appearing overnight.
Honest caveat: almost all of this comes from laboratory and animal studies of the natural cathelicidin peptide, not from controlled human trials of the injectable research product. LL-37 has complex, dose-dependent effects and can even act as a pro-inflammatory signal in the wrong context. It is not an approved medicine and is sold strictly for research use only. None of this is medical advice, talk to a licensed provider before starting anything.
How to take it.
LL-37 is an injection, given subcutaneously into fat with a tiny insulin needle. It isn't an oral peptide, so the injectable form is what people run. The routine is below; for cycling and timing, see the full guide.
Reconstitute the vial
Add bacteriostatic water down the side of the vial (a 5mg vial + 2.5mL = 2mg/mL). Let it dissolve. Swirl gently, don't shake.
Draw your dose
On a U-100 insulin syringe, pull to your unit mark. 200mcg at 2mg/mL is 10 units (0.1mL). Use the calculator if you're unsure.
Pinch and inject
Swab with alcohol, pinch a bit of fat, insert at 45–90°, push slowly. Subcutaneous into the belly is simplest. Start at a low dose and rotate sites.
Rotate your sites
Move to a different spot each time so no area gets sore or lumpy. Store the vial in the fridge between doses.
The easiest spots are the belly (about 2 inches either side of the navel), the love handles, the front of the thigh, and the back of the upper arms. Rotate every injection.
Don't do the math, let the calculator do it.
This is LL-37's typical setup, already worked out. Change any value and the draw updates instantly.
Typical LL-37 dose: about 100–200 mcg once daily, often five days on and two days off, run in short cycles of roughly two to four weeks with a break afterward. Many people start at 100 mcg to test tolerance before going higher.
How to cycle LL-37.
How long people run LL-37, when to take a break, and the honest reasoning behind it.
Often 5 days on, 2 off, in short cycles.
A cycle just means a defined run of time on the peptide, followed by a break. For LL-37 the common pattern is a short run of roughly two to four weeks, then time off, rather than running it indefinitely.
Why not just run it forever? Mostly because the long-term human safety data does not exist yet, and because LL-37 has complex, dose-dependent effects. The cautious and widely followed approach is to run a focused short block, then stop.
- Start at the low end for the first several days before considering a step up.
- Keep the cycle short, commonly two to four weeks, often with two days off each week.
- Take a real break after a cycle before considering another. If symptoms persist, that is a conversation for a licensed provider.
Want the full picture, on and off periods, the washout, stacking, and keeping your results? Read how peptide cycling works →
What's actually in the vial.
For one of these vendors we link the per-batch certificate itself, and the purity below is read straight off it. The rest link to the vendor's general lab-results page. We don't run the labs ourselves and we don't show a purity number unless it's printed on a certificate we link, so you can open the document and check it against the batch yourself.
| Vendor | Purity (per COA) | Batch / report | Certificate |
|---|---|---|---|
| EZ Peptides | 99.503% | EZP-LL371002172026-01 | Janoshik report ↗ |
What people pair it with.
LL-37 is often paired with peptides that cover gut and tissue repair, so the immune and healing angles work together.
Gut & biofilm
The combination people reach for with stubborn gut issues in mind. LL-37 targets microbes and biofilm, KPV calms inflammation, and BPC-157 supports the gut lining and soft tissue.
View stack →Immune support
Two immune-focused peptides run together. LL-37 brings the antimicrobial and anti-biofilm angle; Thymosin α-1 is studied for broader immune modulation.
View stack →Skin & recovery
An add-on for people who want the antimicrobial layer on top of a soft-tissue repair base. BPC-157 and TB-500 cover recovery while LL-37 handles host defense.
View stack →In the same corner.
Other healing and recovery peptides people compare against or pair with LL-37.
Questions, answered straight.
Is LL-37 legal?
LL-37 isn't an approved drug, and it isn't sold for human use. The vendors we compare offer it strictly for research use only. As an unapproved substance it falls under WADA's blanket S0 ban for competing athletes, so they should steer clear. Rules vary by country, so check what applies where you are.
What does research use only actually mean?
It means the product is sold for laboratory and research purposes, not as a supplement or medicine for people. It hasn't been reviewed or approved for human use by the FDA. We aggregate prices and public lab data so you can see the landscape; what you do with that is between you and a licensed provider.
How do I store it?
Keep the sealed, freeze-dried vial in the fridge, and out of direct light. Once you mix it with bacteriostatic water, store it refrigerated and use it within about four weeks. Don't freeze a reconstituted vial.
How often do people dose it?
A common pattern is about 100–200 mcg once daily, often five days on and two off, run in short cycles of two to four weeks with a break afterward. Many start low to test tolerance. Use the calculator to turn your vial and dose into exact units.
Why start at a low dose?
LL-37 has dose-dependent effects, and higher doses are more likely to bring injection-site irritation, flu-like feelings, or gut upset. Starting around 100 mcg and only increasing if it is well tolerated is the cautious, commonly followed approach.