Overview
LL-37 is classified as a healing peptide in Milligram's compound library. 37-amino acid human cathelicidin peptide.
With a half-life of ~4 hours, LL-37 requires daily administration in most observed protocols. Administered via SubQ injection, it has a bioavailability of approximately 95% via its primary route.
Half-life approximately 4 hours. Naturally produced by the body as part of the innate immune system. Subcutaneous administration. One-compartment model.
Mechanism of Action
LL-37's pharmacological activity involves the following key pathways:
Tissue Repair Signaling
LL-37 interacts with cellular repair pathways. Its mechanism involves modulation of growth factors and signaling cascades relevant to tissue recovery.
Systemic Distribution
After subcutaneous administration, LL-37 enters systemic circulation and distributes to target tissues where it exerts its pharmacological effects.
Dosing Protocols
The following protocols represent commonly observed dosing patterns. These are observational summaries, not recommendations.
Dose
50 mcg
Route
Subcutaneous
Frequency
2-3 times daily
Duration
4-12 weeks
Dose
100 mcg
Route
Subcutaneous
Frequency
2-3 times daily
Duration
4-12 weeks
Reconstitution Steps
LL-37 is supplied as a lyophilized (freeze-dried) powder and requires reconstitution before use. Common vial sizes: 5 mg.
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1
Gather Supplies
Collect the LL-37 lyophilized vial, bacteriostatic water, alcohol swabs, a mixing syringe, and insulin syringes for dosing.
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2
Swab Vial Tops
Clean the rubber stoppers on both the LL-37 vial and bacteriostatic water vial with alcohol swabs. Allow to air dry for 10 seconds.
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3
Add Bacteriostatic Water
For a 5 mg vial, slowly inject 2.5 mL of bacteriostatic water along the inner wall of the vial. This yields a concentration of 2,000 mcg/mL for straightforward dose calculation.
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4
Gently Mix
Swirl the vial gently until the powder is fully dissolved. LL-37 can be slow to dissolve due to its larger 37-amino-acid structure. Do not shake or vortex.
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5
Withdraw Your Dose
Using a 100-unit insulin syringe, draw the appropriate volume. For a 5 mg vial reconstituted with 2.5 mL (2,000 mcg/mL), 50 mcg equals 2.5 units and 100 mcg equals 5 units.
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6
Store Properly
Refrigerate the reconstituted vial at 2–8°C immediately after use. LL-37 is sensitive to degradation, so minimize exposure to light and warmth. Use within 3–4 weeks.
Quick Reconstitution Math
5 mg vial + 2.5 mL bac water = 2,000 mcg/mL. For a 50 mcg dose, draw 2.5 units. For 100 mcg, draw 5 units on a 100-unit insulin syringe. Use the Milligram reconstitution calculator for custom vial sizes.
Stable for 3–4 weeks refrigerated at 2–8°C after reconstitution. Lyophilized powder should be stored at -20°C for long-term stability. Avoid repeated freeze-thaw cycles.
Frequently Asked Questions
What is LL-37 and how does it work?
LL-37 is a 37-amino-acid cationic antimicrobial peptide derived from the C-terminal domain of human cathelicidin (hCAP18). It is the only cathelicidin-derived peptide identified in humans. LL-37 exerts broad-spectrum antimicrobial activity by perforating bacterial cell membranes, while simultaneously modulating the innate immune response, promoting angiogenesis, and accelerating wound healing.
What is the half-life of LL-37?
LL-37 has an estimated half-life of approximately 30 minutes in circulation due to susceptibility to proteolytic degradation by serum proteases. This rapid clearance means plasma levels reach steady state within hours of consistent daily dosing. Despite the short circulating half-life, LL-37's downstream immune-modulating and tissue-repair effects persist beyond the plasma elimination window.
How does LL-37 fight infections and biofilms?
LL-37 disrupts bacterial cell membranes through electrostatic interactions between its positively charged residues and negatively charged microbial surfaces. It forms oligomeric channel structures that perforate the membrane, leading to bacterial cell death. LL-37 has also demonstrated anti-biofilm activity against both Gram-positive and Gram-negative pathogens, disrupting established biofilm architecture at sub-antimicrobial concentrations.
How long does LL-37 take to show effects?
Immune-modulating effects are commonly reported within the first 1–2 weeks of consistent administration. Improvements in wound healing and tissue repair are typically observed over 2–4 weeks. Full protocol effects on immune resilience and recovery are generally reported at 6–8 weeks of use.
What are the common side effects of LL-37?
Injection site reactions including mild redness, swelling, or discomfort are the most commonly reported effects. Some users report transient flu-like symptoms during the initial days of administration, which are attributed to immune activation. LL-37 has demonstrated cytotoxicity to human cells at higher concentrations in vitro, which is why conservative dosing with gradual titration is frequently observed in protocols.
Can LL-37 be used alongside other healing peptides?
LL-37 is frequently observed in combination with tissue-repair peptides such as BPC-157 and TB-500 in community protocols. The rationale is complementary mechanisms – LL-37 addresses the antimicrobial and immune-modulating components while BPC-157 and TB-500 focus on tissue regeneration and angiogenesis. Staggering injection times is commonly reported to maintain stable levels throughout the day.