LL-37

What LL-37 does

LL-37 is part of the body's early defense against microbes. Three small wound trials tested it on ulcers; the largest found no overall healing benefit. A tiny melanoma study injected it into tumors, and two COVID studies used bacteria engineered to make it. These studies do not validate routine injections under the skin. Inflammation, reproductive effects and tumor signals are key unresolved risks.

• In a small trial on leg ulcers, the two lower strengths improved early healing, though a larger trial found no overall benefit. (Studied in a trial)
• In a small foot-ulcer trial in diabetes, it helped healthy new tissue form in the wound, but wound size did not shrink more. (Studied in a trial)
• In lab and animal studies, it helped new blood vessels grow. (animal)
• Forum users report injecting it for infection, gut or immune goals; one reported improvement, without giving a dose. (Reported by users)

Uses in the sources

• Studied on chronic venous and diabetic foot ulcers. The larger venous-ulcer trial found no overall benefit; a small foot-ulcer trial improved a tissue-growth score. (Studied in a trial) (source)
• Exploratory melanoma research used injections directly into tumors. Four enrolled and only three appeared in posted results. (Studied in a trial) (source)
• COVID studies used engineered L. lactis capsules, not purified LL-37. The randomized study did not improve viral clearance overall. (Studied in a trial) (source)
• Forum users discuss injections for infection, gut or immune goals. No controlled human subcutaneous trial was found. (Reported by users) (source)

LL-37 dosage

Typical reported dose: 100–125 mcg once a day

• First wound trial: 0.5 mg/mL: 0.5 mg/mL LL-37 applied to the ulcer twice weekly for 4 weeks. twice weekly, on the skin. Studied in a trial. Studied in: Adults with hard-to-heal venous leg ulcers. (source)
• First wound trial: 1.6 mg/mL: 1.6 mg/mL LL-37 applied to the ulcer twice weekly for 4 weeks. twice weekly, on the skin. Studied in a trial. Studied in: Adults with hard-to-heal venous leg ulcers. (source)
• First wound trial: 3.2 mg/mL: 3.2 mg/mL LL-37 applied to the ulcer twice weekly for 4 weeks. twice weekly, on the skin. Studied in a trial. Studied in: Adults with hard-to-heal venous leg ulcers. (source)
• HEAL: 0.5 mg/mL: 0.5 mg/mL at 25 microlitres/cm², giving 12.5 mcg/cm² per application. twice weekly, every 3 ± 1 days, on the skin. Studied in a trial. Studied in: Adults with hard-to-heal venous ulcers receiving compression. (source)
• HEAL: 1.6 mg/mL: 1.6 mg/mL at 25 microlitres/cm², giving 40 mcg/cm² per application. twice weekly, every 3 ± 1 days, on the skin. Studied in a trial. Studied in: Adults with hard-to-heal venous ulcers receiving compression. (source)
• Foot-ulcer cream: 0.5 mg/g: 0.5 mg/g cream; 0.025 mL cream/cm² of wound, twice weekly for 4 weeks. twice weekly, on the skin. Studied in a trial. Studied in: Adults with mildly infected diabetic foot ulcers. (source)

These are doses reported in labels, trials or user reports, not a personal plan. Check the source behind each one.

Work out syringe units with the dosing calculator

How to mix LL-37

Comes as: Trial topical gel or cream, Community lyophilised powder vials, Engineered bacterial capsules in COVID studies.

Mixed with: Community posts describe bacteriostatic water. HEAL used a sterile PVA diluent for topical application, not bacteriostatic injection water..

Common vial sizes: 5 mg. Common water amounts: 4 mL.

• An independent discussion describes a 5 mg vial with 4 mL bacteriostatic water. This does not establish stability or sterility.
• Topical trial concentrates were mixed with 13.1% PVA to make 0.5 or 1.6 mg/mL LL-37 in 10.5% PVA.
• No evidence supports a universal 28-day expiry after mixing. Sterility and chemical stability are separate questions.

Before mixing: No approved vial-storage label or validated expiry for community products was found.

After mixing: No validated shelf life for community mixtures. The wound trial mixed its controlled formulation immediately before application.

LL-37 side effects and risks

Reported side effects

• Redness, swelling or irritation around ulcers: Pooled across all arms: ulcer redness 42.6%, swelling 39.2%; nearby skin redness 54.1%. No consistent excess versus placebo., mild. Assess local changes at each dressing change. (source)
• Adverse events during topical treatment: Any event: 20/48 at 0.5 mg/mL, 24/49 at 1.6 mg/mL, 20/51 placebo. These are not all drug caused., moderate. Review new symptoms; topical trial results do not describe injected-product safety. (source)
• Serious events during topical study: 11/148, 7.4%, across all arms. None was judged related to study drug; no deaths., serious. Seek urgent assessment of serious symptoms. (source)
• Irritant dermatitis in foot-ulcer trial: 1/13 active participants; attributed to excess wound fluid rather than LL 37 itself., mild. Have wound care reassessed. (source)
• Immune reactions or inflammatory flares: FDA flags immune reaction risk; systemic incidence is unknown. Laboratory work links LL 37 to autoimmune signaling., serious. New rash, swelling or systemic worsening needs assessment. (source)
• Symptoms reported after community use: One user described persistent spinal spasms and dry hair after a 4 week course; causation was not verified., moderate. Obtain assessment rather than using another untested peptide to reverse symptoms. (source)

Stop and get help if

• Breathing trouble, tongue or throat swelling, or fainting: Stop and get emergency care immediately.
• Spreading hot redness, increasing wound pain or fever: Seek urgent assessment for wound infection; LL-37 is not a proven substitute for infection care.
• New severe symptoms after an injection or rapidly worsening skin disease: Stop and seek prompt medical review; do not assume this is a helpful immune or detox response.

Who should avoid it

• pregnant: Precautionary block. Pregnancy was excluded from human trials; fetal safety is unknown.
• breastfeeding: Precautionary block. Breastfeeding was excluded; infant exposure and effects are unknown.
• tryingToConceive: Sperm-damaging effects occurred in lab and mouse work. Human reproductive risk from dosing is unknown.
• under18: No pediatric dosing or safety regimen established; human dosing studies were in adults.
• activeCancer: Precautionary block outside oncology research. FDA cites tumor-promoting findings in some tissues; LL-37 also promotes vessel growth.
• cancerHistory: Discuss prior cancer with oncology. Effects depend on the tissue and are not established by the three-person melanoma results.
• autoimmuneDisease: LL-37 can drive self-DNA immune signaling. Active autoimmune disease was excluded from the melanoma study.
• immunosuppressed: The melanoma trial excluded immune deficiency and systemic steroids; infection and immune effects remain uncertain.
• kidneyDisease: Human systemic clearance and kidney dose adjustments are unknown; the melanoma trial imposed kidney-function limits.
• liverDisease: No established liver dose adjustment; the melanoma trial required acceptable bilirubin, ALT and AST.
• other: Avoid re-exposure after a serious allergy to LL-37 or its formulation.
• testedAthlete: S0 prohibits unapproved pharmacological substances at all times. Verify status with the relevant anti-doping body.

Interactions

• Systemic steroids and other immunosuppressants: Immune effects may conflict. This is a precaution, not a proven interaction; systemic steroids were excluded from the melanoma trial.
• Other immune-active peptide stacks: No human combination trial found. Duplicate LL-37 exposure and multi-peptide immune effects have no established safety limits.

Product quality risks

• FDA flags immune reactions, peptide impurities and difficulty characterizing the active ingredient.
• Unregulated peptides may contain the wrong amount or ingredient, microbes or endotoxins; these risks lack LL-37-specific market rates.
• Trial material underwent content, impurity and identity testing. A research-vial label does not establish equivalent quality.

What to expect

Six intervention studies: three topical wound trials, one registry-only tumor-injection trial, and two engineered-bacteria oral studies, including one preprint.

Key studies

• Phase I/II wound dose trial: The two lower strengths improved early healing measures; 3.2 mg/mL did not. (source)
• HEAL LL-37: Neither strength improved complete wound closure overall. (source)
• Diabetic foot-ulcer cream: LL-37 improved granulation, but wound-area and bacterial outcomes did not differ significantly. (source)
• Phase I/II melanoma injections: Posted results describe three treated patients; this is far too small to establish cancer benefit. (source)
• Oral bacterial-delivery pilot: The uncontrolled preprint reported symptom improvements and no adverse reactions. (source)
• Oral bacterial delivery in COVID: Viral clearance did not differ overall; an early-treatment subgroup had a signal. (source)

LL-37 FAQ

• Is LL-37 FDA-approved? No FDA-approved product or label. FDA warns of immune reactions, peptide impurities, reproductive harm and tissue-specific tumor effects.
• How do people take it? Under the skin, once daily. Up to 6 weeks, as discussed. Source: reported by users, not an established dose.
• What's the difference between LL-37 and Thymosin alpha-1? LL-37: a human defense peptide with mixed topical wound-trial results and no established injection regimen. Thymosin alpha-1: an immune-signaling peptide with overseas approvals and mixed trial results. Why people pair them: discussed with LL-37 for immune goals in a proposed autoimmune stack.
• Can I take it with Thymosin alpha-1? Discussed with LL-37 for immune goals in a proposed autoimmune stack. No combination trial; effects on autoimmune disease may be unpredictable. Source: reported by users. Ask a doctor before combining anything.
• Is it banned in sport? Yes. It is banned in and out of competition (WADA 2026). Inferred from S0 for unapproved pharmacological substances. Neither peptide is named individually; athletes should verify with their anti-doping body.
• How long does a mixed vial last? No validated shelf life for community mixtures. The wound trial mixed its controlled formulation immediately before application.