What is LL-37?

What the name refers to

LL-37 is a peptide sequence belonging to the human cathelicidin family. The name comes from the sequence itself: it begins with two leucine residues and is 37 amino acids long. What is sold under that name is a synthetic copy, shipped as a dry powder in a sealed glass vial.

That powder is the entire product. It has no volume you can measure and no dose you can draw until water is added. Everything on this page concerns that step and nothing else.

This site does not describe what LL-37 does in a body, what it is used for, or what happens after it is administered. Those are clinical questions. DoseGraph has no medical review process and does not answer them.

Regulatory status

LL-37 is not approved by any regulator for human use. It has no approved label, no approved indication, no approved dosing schedule and no approved route. There is no package insert to consult because no regulator has ever reviewed one.

This matters for a practical reason beyond legality. When a compound is approved, the dose figures that circulate trace back to a document a regulator examined. When it is not approved, the figures circulating are whatever sellers and forum posts happen to say. The amounts appearing on vendor listings for LL-37, commonly 0.1 mg, 0.25 mg and 0.5 mg, are listing conventions. They are not recommendations, and this page treats them only as example inputs for arithmetic.

Material sold without oversight also carries no guarantee that the vial contains what the label says, at the purity the label says, in the mass the label says. Every calculation below assumes the labeled mass is correct.

What is not known

There is no reliable human pharmacokinetic data for LL-37. Because of that, this site makes no claim about its half life, how long it takes to clear, whether it accumulates with repeated administration, or how long any effect might persist.

That gap is larger than it sounds. Without pharmacokinetics there is no basis for choosing an interval between doses, no basis for scaling to body weight, and no basis for calling a given amount small or large in any meaningful sense. Anyone presenting a schedule for LL-37 as though it were derived from data is presenting something else.

What can be calculated is concentration. Concentration is a ratio of two things you control directly: the mass stated on the vial and the volume of bacteriostatic water you add. It involves no biology and no assumption about what happens after the syringe is emptied.

Reading the concentration table

The table on this page covers the two vial sizes sold, 5 mg and 10 mg, against the three water volumes commonly used, 1 mL, 2 mL and 3 mL. Three things in it are worth pulling out.

First, the numbers are a simple division. Milligrams in the vial divided by milliliters of water added equals milligrams per milliliter. The peptide powder does not add meaningful volume, so the water volume you add is the final volume you measure from.

Second, doubling the water halves the concentration. A 5 mg vial in 1 mL gives 5 mg/mL; the same vial in 2 mL gives 2.5 mg/mL. The vial still holds 5 mg either way. You have not changed the amount of peptide, only how spread out it is.

Third, vial size and water volume can cancel. A 10 mg vial in 2 mL and a 5 mg vial in 1 mL both give 5 mg/mL. The larger vial holds twice as much peptide, so it yields twice as many draws of the same size, but each identical draw carries an identical amount. Concentration, not vial size, is the number to track once the vial is mixed.

Turning concentration into a syringe measurement

A syringe is marked in volume, not in milligrams. The working order is always the same: fix the concentration first, convert the amount you intend to draw into a volume, then read that volume off the barrel.

The conversion is division. Take the amount in milligrams and divide it by the concentration in milligrams per milliliter. The result is a volume in milliliters. On a U-100 insulin syringe the full 1 mL barrel is divided into 100 units, which lets you carry that volume onto the unit scale.

A thinner solution requires a larger draw for the same amount of peptide. More water buys finer resolution on the syringe scale at the cost of a larger volume per draw. Less water does the reverse, concentrating the same peptide into a smaller measured volume where a small misread represents a larger error in milligrams.

Whichever you choose, write the water volume on the vial. Once dissolved, the solution looks the same at every concentration in the table. There is no way to recover the number by looking at it.

What we do not know

We hold no reliable human pharmacokinetic data for LL-37, so this site makes no claims about its half life, how long it takes to clear, or how it accumulates. The arithmetic below concerns concentration and volume only.

This page answers arithmetic and handling questions. It does not tell you what dose to take, what to expect, or whether anything is appropriate for you, and there is no medical review behind it.

Common questions

Is LL-37 approved for human use?

No. LL-37 is not approved by any regulator for human use. There is no approved label, indication or dosing schedule. Anything presented as a standard protocol is not derived from a regulatory review.

What is the half life of LL-37?

This site does not state one. There is no reliable human pharmacokinetic data for LL-37, so no claim is made here about its half life, clearance or accumulation. Figures circulating elsewhere are not something this page can verify.

How much bacteriostatic water should I add to a 5 mg vial?

That is a choice, and this site does not recommend one. The table shows what each option produces: 1 mL gives 5 mg/mL, and adding more water gives a proportionally thinner solution. Less water means a smaller measured volume per draw, more water means a larger one.

Does a 10 mg vial give a stronger solution than a 5 mg vial?

Not necessarily. Concentration depends on both mass and water volume. A 10 mg vial in 2 mL and a 5 mg vial in 1 mL both give 5 mg/mL. The 10 mg vial simply holds more total peptide, so it yields more draws of the same size.

Why do vendor listings show amounts like 0.1 mg or 0.5 mg?

Those are seller conventions, not amounts established by any regulator or clinical review. They appear here only as example inputs to show how the arithmetic works. This site does not endorse them or suggest any amount.