LL-37 5 mg vial dosage

What LL-37 is

Class:

Human cathelicidin antimicrobial peptide (37 residues, the C-terminal fragment of the hCAP18/CAMP precursor protein)

Also called:

Cathelicidin LL-37, hCAP18 (37-146), CAMP gene product

Used for:

An antimicrobial peptide naturally present in human neutrophils, skin and mucosal surfaces. Sold as a research chemical for innate-immune and antimicrobial research; FDA has not approved it for any human use.

Human evidence:

Limited human data. LL-37 is naturally present in the human body, so it has a large biomarker literature: an NCBI PubMed search for "LL-37" or "cathelicidin LL-37" (queried 24 September 2026) returns over 2,500 records, 60 of them tagged as the clinical-trial publication type. The great majority of that literature measures a person's own LL-37 levels as a marker of infection or inflammation; it is not evidence that dosing a person with synthetic LL-37 is safe or effective. Four small trials have given people LL-37: two of a topical solution on venous leg ulcers (34 and 148 people; the larger found no significant improvement in healing over placebo across the whole group), one of a cream on diabetic foot ulcers, and one of an oral product of bacteria engineered to make LL-37 in people in hospital with COVID-19. None tested an injection. FDA's bulk drug substance review states it lacks sufficient safety-related information regarding cathelicidin LL-37 to know whether the drug would cause harm when administered to humans, and cites nonclinical findings raising reproductive and protumorigenic concerns.

US status:

Research use only. Not FDA-approved for any use, and DailyMed, FDA's own drug-label database, returns zero results for "LL-37" (searched 24 September 2026). Cathelicidin LL-37 sits in the "bulk drug substances nominated but withdrawn" table on FDA's compounding safety-risk page (content current 22 April 2026) - a nomination for lawful 503A compounding that was withdrawn by the nominator, with FDA's safety-risk language kept on the page. It has no USP or NF monograph, is not a component of any FDA-approved drug, and is not on the 503A Bulks List, so it is not currently eligible for lawful compounding. It was not on the agenda of FDA's July 2026 Pharmacy Compounding Advisory Committee meeting.

The full picture, with every study: LL-37 guide.

How to mix a 5 mg LL-37 vial

For this vial: 1 mL of bacteriostatic water makes 5 mg/mL, so 1 mg is 20 units (0.2 mL) on a U-100 insulin syringe. Pick a different volume from the units table if you want bigger or smaller draws; the number of doses stays the same.

1. Wipe the rubber stoppers of both the peptide vial and the bacteriostatic water vial with an alcohol swab and let the alcohol dry. ^[3][4]
2. With a new sterile needle and syringe, draw up the amount of bacteriostatic water you have chosen for the dilution. ^[3][4][5]
3. Inject the water into the peptide vial by aiming the stream against the inside glass wall, which helps prevent foaming. ^[6]
4. Swirl or roll the vial gently until the powder has fully dissolved; do not shake it. Do not inject the solution if it is cloudy or has particles in it. ^[3][4][6]
5. Label the vial with the date and time it was mixed, the amount of water added and how long it can be used after mixing. ^[3]
6. Store the mixed vial in the refrigerator at 2-8°C (36-46°F) and do not freeze it. ^[6]

Step by step with pictures: how to reconstitute peptides. About the water itself: bacteriostatic water.

Storing LL-37 vials

• Freeze-dried (lyophilized) peptide keeps far longer than peptide in solution; peptide suppliers advise storing the powder at -20°C away from bright light. ^[7]
• Protect peptide vials from heat and light. ^[7][8]
• Avoid repeated freeze-thaw cycles; a prescription peptide label also says not to freeze a vial once it has been mixed. ^[6][7]
• Once a multi-dose vial, such as bacteriostatic water, has been opened (needle-punctured), date it and discard it within 28 days unless its manufacturer states another date. ^[9][10]

More detail: peptide storage and shelf life.

Injecting safely

• Clean the injection site with an alcohol swab and let the skin dry completely before injecting. ^[11][12]
• Pinch up a fold of skin and fat (not muscle) and insert the needle at a 45- to 90-degree angle: 90 degrees where there is enough fatty tissue, 45 degrees where there is little. ^[11][12][13]
• Pulling back on the plunger (aspiration) is not necessary for a subcutaneous injection, because the chance of the needle being in a blood vessel is small. ^[11]
• Inject slowly, at roughly 10 seconds per mL. ^[11]
• Common sites are the belly, the thigh and the upper arm; rotate sites, keeping each injection at least 1 inch (2.5 cm) from the last. ^[6][11][12]

Hygiene and warning signs

• Use a new sterile needle and syringe for every injection and every time you enter a vial; never reuse them. ^[5][9][12]
• Never share needles, syringes or pens with anyone, even if the needle is changed; unsafe injection practices spread hepatitis B, hepatitis C and HIV. ^[5][8][9]
• Put used needles and syringes in a sharps disposal container straight away (FDA-cleared if possible), never loose in the trash, recycling or toilet, and dispose of the container following your community's guidelines. ^[14][15]
• Contact a health care provider if the injection site shows signs of infection, such as redness, swelling, red streaks or a fever. ^[12]

Where to inject: subcutaneous injection sites.

How LL-37 works

• LL-37 is a 37-amino-acid, helical, amphipathic peptide and the only cathelicidin-derived antimicrobial peptide found in humans; its gene is the only cathelin-family gene in the human genome. ^[16][17]
• The body makes it as part of a larger precursor, hCAP-18, stored in neutrophils. LL-37 is cut free after neutrophils release hCAP-18, by the enzyme proteinase 3; no cleavage was detected inside neutrophils after they had engulfed microbes. ^[17][18]
• It is made in skin, gut and airway lining cells and in several kinds of white blood cell. Besides killing a broad range of microbes, it regulates inflammation, attracts immune cells to wounds and infection sites, binds and neutralises bacterial endotoxin (LPS) and promotes wound closure. ^[16]
• LL-37 also triggers new blood-vessel growth by acting on the formyl peptide receptor-like 1 (FPRL1) on endothelial cells, shown in cultured cells and in chick-embryo and rabbit models. ^[19]

What the LL-37 research found

Human evidence: limited human data. Each result says what was studied.

• Human studyIn a 2014 first-in-human randomised, double-blind trial in 34 people with hard-to-heal venous leg ulcers, topical LL-37 at 0.5 and 1.6 mg/mL gave healing rates about six and three times placebo (p = 0.003 and p = 0.088); the highest strength, 3.2 mg/mL, did no better than placebo. ^[20]
• Human studyA larger 2021 phase IIb trial of topical LL-37 (0.5 or 1.6 mg/mL) plus compression in 148 people with hard-to-heal venous leg ulcers found no significant improvement in healing over placebo across the whole group; a post hoc look suggested benefit only in ulcers of at least 10 square centimetres. ^[21]
• Human studyIn a 2023 randomised, double-blind trial in diabetic foot ulcers with mild infection, LL-37 cream applied twice a week for 4 weeks raised the granulation index more than placebo, but did not lower IL-1 alpha, TNF-alpha or bacterial colonisation. ^[22]
• Human studyIn a 2023 open-label randomised trial in 238 adults in hospital with Omicron COVID-19, an oral product - Lactococcus lactis bacteria engineered to make LL-37 - shortened the time to a negative SARS-CoV-2 RNA test (mean 9.80 vs 14.04 for placebo; the abstract does not state the unit). ^[23]
• Lab studyIn human skin, hCAP-18/LL-37 rises sharply after wounding but is low in chronic ulcers and absent from the epithelium at the ulcer edge; in organ-cultured human skin, antibodies against LL-37 blocked wound re-epithelialisation. ^[24]
• Lab studyIn psoriasis, LL-37 binds the body's own DNA and turns it into a trigger for interferon production by plasmacytoid dendritic cells, a pathway the researchers propose may drive the autoimmune reaction. ^[25]

LL-37 side effects and risks

The human safety data come from short trials of LL-37 applied to wounds or taken by mouth as engineered bacteria; none of the trials I read tested it by injection.

• Human studyIn the 34-person venous leg ulcer trial of topical LL-37, there were no safety concerns about local or systemic adverse events. ^[20]
• Human studyIn the 148-person phase IIb leg ulcer trial, topical LL-37 was reported as well tolerated and safe at both strengths tested. ^[21]
• Human studyIn the 238-person COVID-19 trial of oral LL-37-producing bacteria, no severe adverse events were seen during the hospital stay and follow-up. ^[23]
• Regulator reviewFDA states it lacks sufficient safety information to know whether cathelicidin LL-37 would cause harm when given to humans, and flags a possible risk of immunogenicity for certain routes and complexities with peptide-related impurities and characterisation of the active ingredient. ^[26]
• Regulator reviewFDA notes nonclinical research findings suggesting that LL-37 has detrimental effects on male reproduction and can promote tumours in some tissues. ^[26]

Other things to know

• FDA states it lacks sufficient safety-related information regarding cathelicidin LL-37 to know whether the drug would cause harm when administered to humans.
• FDA cites nonclinical research suggesting detrimental effects on male reproduction and protumorigenic effects in some tissues.
• FDA flags a risk for immunogenicity for certain routes of administration, and complexities in peptide-related impurities and active-ingredient characterisation.
• The large published literature on LL-37 mostly studies the peptide the body already makes; it is not safety or efficacy evidence for an injected or topical research-chemical product.

Reported side effects and what the studies measured: LL-37 side effects.

Where this vial size comes from

LL-37 is sold as a 5 mg vial by the pages below, each checked on the date shown. I list them as evidence that this size exists, not as a recommendation to buy from them.

• SwissChemsvendorLists it as: "LL-37 (CAP-18) 5mg"; Total Compound Content: 5mg (1 vial) · checked 2026-09-28
• BioEdge Research LabsvendorLists it as: "Vial Size: 3 mL sterile vial"; "Fill: 5mg" · checked 2026-09-28

The doses come from the sourced common protocol on the LL-37 dosing page, and every number on this page is arithmetic on those doses and this vial size.

Where to buy LL-37 for research

Sold for research use only. Listed by Next Level Pharm and BioEdge Research Labs; compare them on my vendors page or see the listing on the LL-37 page.

Questions

How much water do I add to a 5 mg LL-37 vial?

There is no single correct amount: water changes how many units a dose is, not how many doses the vial holds. With 1 mL the vial is 5 mg/mL and 1 mg is 20 units (0.2 mL) on a U-100 insulin syringe. The units table gives 1, 2, 5 mL.

How many doses are in a 5 mg LL-37 vial?

50 doses at 100 mcg, 5 doses at 1 mg, 2 doses at 2 mg.

How long does a 5 mg LL-37 vial last?

At 1 mg a dose and 3-5 times weekly to once daily, about 0.7-1.7 weeks. How long a mixed vial keeps is a separate limit; see storage below.

How many 5 mg vials do I need for a cycle?

1 vial at 100 mcg 3 times a week for 4 weeks; 34 vials at 2 mg 7 times a week for 12 weeks.

What does 1 unit equal in a 5 mg LL-37 vial?

50 mcg with 1 mL, 25 mcg with 2 mL, 10 mcg with 5 mL of bacteriostatic water, on a U-100 syringe.