What is the LL-37 peptide?
The LL-37 peptide is the active form of human cathelicidin, the only cathelicidin-family antimicrobial peptide found in humans. It is 37 amino acids long and begins with two leucines, which is where the name comes from. In the body it is cleaved from a larger precursor protein called hCAP18, and it has been studied in laboratory research as part of the innate immune system.
Its length matters for the math only indirectly. LL-37 is much larger than a short research peptide such as the KPV tripeptide, so a milligram of it holds fewer individual molecules, and supplier handling notes tend to be more detailed. For the calculator, the mg on the label and the volume of liquid added are still the only inputs.
Research vials of LL-37 are sold as a freeze-dried powder, most often in a 5 mg size. This page covers only the math: how much BAC water goes into an LL-37 vial, what concentration results, and how an amount you already have converts into units on a U-100 syringe.
How much BAC water for an LL-37 vial?
There is no single correct volume. Less water makes a stronger solution with more micrograms in every syringe unit; more water makes a weaker one that spreads the same amount across more units and is easier to read. The chart shows micrograms per U-100 unit for a 5 mg LL-37 vial at several water volumes, with a 10 mg column included for comparison.
| BAC water | 5 mg vial | 10 mg vial |
|---|---|---|
| 1 mL | 50 mcg/unit 5 mg/mL | 100 mcg/unit 10 mg/mL |
| 2 mL | 25 mcg/unit 2.5 mg/mL | 50 mcg/unit 5 mg/mL |
| 2.5 mL | 20 mcg/unit 2 mg/mL | 40 mcg/unit 4 mg/mL |
| 5 mL | 10 mcg/unit 1 mg/mL | 20 mcg/unit 2 mg/mL |
Each cell shows mcg per unit on a U-100 syringe (100 units = 1 mL) and the resulting concentration.
Down each column, every step up in water lowers the micrograms per unit in proportion. Doubling the water halves the concentration. The BAC water to peptide ratio guide walks through that relationship for any vial size.
If a supplier specifies a particular volume, find that row in the chart: the value in it is the micrograms held in each unit at that volume. If your volume is not listed, the calculator handles any volume you enter.
LL-37 5 mg reconstitution: worked example
The math has three steps: vial mg ÷ water mL = mg per mL; amount ÷ concentration = mL; and mL × 100 = units on a U-100 syringe. For a 5 mg vial, for example, if the amount you already have is 175 mcg:
The math: 5 mg ÷ 2 mL = 2.5 mg/mL (2,500 mcg/mL), which is 25 mcg per unit. 175 mcg ÷ 2,500 mcg/mL = 0.07 mL = 7 units on a U-100 syringe.
With the same vial mixed in more water, for example, if the amount you already have is still 175 mcg:
The math: 5 mg ÷ 2.5 mL = 2 mg/mL (2,000 mcg/mL), which is 20 mcg per unit. 175 mcg ÷ 2,000 mcg/mL = 0.0875 mL = 8.75 units on a U-100 syringe.
The amount did not change, but the weaker solution means it occupies more liquid and more units. Units are the same size on every U-100 syringe; the U-100 syringe units to mL chart shows how they map to mL.
LL-37 peptide calculator: what the numbers mean
The chart and calculator on this page are conversion tools. You enter the vial size, the water volume, and an amount you already have; the tool returns the concentration, the liquid volume, and the U-100 syringe units. That is all it does.
No row in the chart is a recommendation, and nothing here sets an amount, schedule, or route for the LL-37 peptide. Those belong to the product labeling and a qualified professional. To check any result by hand, use the peptide calculator math check.
LL-37 reconstitution notes from suppliers
LL-37 is much longer than most short research peptides, and supplier material sometimes reflects that:
- Solvent. Some suppliers list bacteriostatic water, while others specify sterile water or a dilute acetic acid solution for LL-37 reconstitution. Whatever the label names takes priority over any general guide.
- Dissolving. Some suppliers note that longer peptides can foam if shaken and advise adding water slowly down the vial wall and swirling gently.
- Appearance. A clear solution is what suppliers generally describe. Cloudiness or particles are a reason to contact the supplier.
- Storage. Some suppliers specify refrigeration after mixing. A punctured BAC water vial follows its own label and the common 28-day guidance for opened multi-dose vials.
For the general sequence of steps, read how to reconstitute peptides.
Is LL-37 FDA-approved?
LL-37 is not an FDA-approved drug. Research-labeled vials sold online are not approved medicines, and their identity, purity, and sterility depend entirely on the supplier. A correct calculation cannot confirm any of those things.
Different suppliers can label the same compound in different ways, so compare the name, the mg amount, and any stated solvent on each vial rather than assuming two LL-37 products are identical.
LL-37 FAQ
What is the LL-37 peptide?
LL-37 is the active form of human cathelicidin, a 37-amino-acid peptide that begins with two leucines. It is cleaved from the precursor protein hCAP18 and is sold for research as a freeze-dried powder.
How much BAC water goes in a 5 mg LL-37 vial?
There is no single correct volume. More water gives fewer micrograms per syringe unit, less water gives more. Some suppliers specify a particular solvent or volume, and the product label takes priority.
Can LL-37 be mixed with something other than BAC water?
Some suppliers specify sterile water or a dilute acetic acid solution for LL-37. The calculator math is the same for any liquid, because only the volume affects concentration. Follow the product label.
Does this page give an LL-37 dose?
No. The calculator converts an amount you already have into concentration, mL, and U-100 syringe units. Amount, schedule, and route belong to the product labeling and a qualified professional.