A TB-500 vial arrives as a dry film at the bottom of a small glass tube, and the label tells you one thing: the mass of powder inside. Two, five or ten milligrams. That number is not a dose and not a volume. Reconstitution turns the mass into a liquid you can measure, and it is arithmetic before it is technique — you choose the water, the water sets the concentration, and the concentration decides what one mark on the syringe is worth. This is general information about mechanics and arithmetic, not medical advice.

What is actually in the vial

TB-500 is a trade name rather than a chemical one, and it covers two molecules depending on who sold it. In most of the research literature it means a short synthetic fragment, Ac-LKKTETQ — seven amino acids corresponding to residues 17 to 23 of thymosin beta-4, a naturally occurring 43-amino-acid protein. Several suppliers sell the full 43-amino-acid sequence under the same label, and say so on the listing. For the mixing, that changes nothing about the method and everything about what can be assumed: the arithmetic works from the milligrams printed on the label, and the label, with whatever certificate of analysis came with it, is the only thing saying what those milligrams are.

The regulatory position deserves one plain sentence. TB-500 is not approved by the FDA for human use and is sold as a research chemical; it sits on the World Anti-Doping Agency's prohibited list under S0, the category for non-approved substances, banned in and out of competition, and the US Department of Defense has adopted the same categories for its own testing. What the compound is claimed to do is outside the scope of this page. What follows is how to dissolve a known mass into a known volume.

How to reconstitute TB-500, step by step

Vials ship lyophilized, most commonly at 2 mg, 5 mg and 10 mg, sometimes in multi-vial kits. The powder is a thin film or a small cake, and in a 2 mg vial it can be nearly invisible against the glass. That is normal.

Turning the vial into units

Once it is liquid, everything is division. The vial's milligrams divided by the millilitres of water gives the concentration; the rest is unit conversion.

mg in vial ÷ ml of water = mg/ml  ·  × 1,000 = mcg/ml  ·  ÷ 100 = mcg per unit

As an example, purely to run the maths: a 5 mg vial reconstituted with 2 ml of bacteriostatic water sits at 2.5 mg/ml, or 2,500 mcg/ml, so each mark on a U-100 barrel holds 25 mcg. A 2 mg vial with 1 ml lands at 20 mcg per mark — and so does a 10 mg vial with 5 ml, because the ratio is what the syringe sees, not the vial size.

The water never changes how much peptide is in the vial. Ten milligrams is ten milligrams in 1 ml or in 5 ml. What it changes is how many marks that total is spread across, and so whether the amount you need lands on a line you can read.

The amount to administer is not something to be reasoned out from a chart — it comes from a qualified clinician, and this arithmetic only translates it into a position on the barrel. If you would rather not do the division at every vial, that conversion is what the Vialog calculator runs.

Storage, and the clock that starts at first entry

Lyophilized powder is the stable form; kept dry, cold and out of the light it lasts far longer than anything in solution, which is why vials ship that way. Reconstituted is a different object: refrigerate it at 2 to 8 °C, in the body of the fridge rather than the door where the temperature swings, and do not freeze it — ice crystals are hard on peptides in solution. The in-use window is then set by the water, not by the peptide. Bacteriostatic water for injection is labelled for use within 28 days of the first puncture, and that clock starts when the stopper is pierced, not when the vial is emptied. Writing the date on the vial takes two seconds and removes the question later.

Where it goes wrong

Five failures cover most of them. Reading the vial's total as though it were a single dose. Slipping between milligrams and micrograms, a factor of a thousand in whichever direction it happens. Adding the water before doing the arithmetic, then finding the amount lands below one mark where there is no line to read. Shaking rather than swirling. And drawing with a U-40 syringe, where each mark is 0.025 ml instead of 0.01 ml, so every U-100 figure comes out 2.5 times off.

This is general educational information about reconstitution mechanics and unit arithmetic. It is not medical advice and not a dosing recommendation. What to administer, and whether to administer anything at all, is a decision for a qualified healthcare professional.

Frequently asked

How much bacteriostatic water goes into a 5 mg TB-500 vial?

There is no fixed answer, because the volume is a choice about readability rather than a property of the vial. Adding 2 ml gives 2.5 mg/ml and 25 mcg per mark on a U-100 barrel; adding 1 ml gives 5 mg/ml and 50 mcg per mark. The right volume is the one that puts the amount your clinician specified on a whole line you can read.

Can sterile water be used instead of bacteriostatic water?

It dissolves the powder identically, but it contains no preservative, so the vial has no protection against contamination once it has been entered. Bacteriostatic water contains 0.9% benzyl alcohol for that purpose and is what makes a multi-entry vial workable. Sterile water is generally treated as single-use.

How long does reconstituted TB-500 keep in the fridge?

The limit comes from the water. Bacteriostatic water for injection is labelled for 28 days from the first puncture, refrigerated at 2 to 8 °C, and that window applies to whatever is dissolved in it. Cloudiness, colour change or visible particles end it early regardless of the date.

Does shaking a TB-500 vial ruin it?

Vigorous shaking introduces shear and foaming, both of which are unkind to peptides in solution, and it is never necessary. Gentle swirling or rolling dissolves a lyophilized film perfectly well; if it has not gone clear after a few minutes, more time is the answer rather than more force.

Why do two TB-500 vials give different unit readings for the same amount?

Because a unit is a mark of volume — 0.01 ml on a U-100 barrel — and not an amount of drug. How much peptide sits in that 0.01 ml depends on the vial's milligrams divided by the water added. Two vials mixed at different concentrations will read as different numbers of marks for exactly the same quantity.

Keep reading: How to reconstitute a peptide · How much bacteriostatic water to add.