TB-500: A Reconstitution Walkthrough (and the mg/mcg Trap)

TB-500 is almost always the second peptide someone reconstitutes, immediately after BPC-157. That order matters more than it sounds, because habits built on one vial carry over to the next. Some instructions are written in micrograms, others in milligrams. Same syringe, same arithmetic, numbers a thousand times apart.

The trap, stated plainly

1 mg is 1000 mcg. If an amount is written in milligrams and you type that number into a field expecting micrograms, you have asked for a thousandth of it. Type the microgram figure into a field expecting milligrams and you have asked for a thousand times it — for a vial of a few milligrams, many times the entire contents.

Both mistakes are invisible in the arithmetic — the maths is correct in each case, it is the units that are wrong. This is why the calculator warns when a single dose exceeds the whole vial: that specific warning exists almost entirely to catch a mg/mcg mix-up, because there is no legitimate reason to draw more peptide than the vial contains. VialPal does not supply the amount: enter the dose and concentration from your clinician, pharmacy, product instructions, or research protocol. VialPal handles the math.

The vial sizes you'll meet

TB-500 is typically supplied as 2 mg, 5 mg, 10 mg of lyophilised powder. Concentration is the milligrams in the vial divided by the millilitres of water added, and on a U-100 syringe (100 units to 1 mL) that fixes how many micrograms each unit mark carries:

To turn that into a draw, divide the dose from your instructions, in micrograms, by the mcg per unit for your vial. The result is the number of units. A 0.3 mL syringe holds 30 units, a 0.5 mL syringe 50 and a 1 mL syringe 100 — if the result is larger than the barrel you own, the draw does not fit, however correct the arithmetic.

Note the last row against the fourth: the same 10 mg vial gives very different mcg per unit purely from how much water went in, so the diluent choice can move a draw between “fits” and “does not fit”. Decide the water volume by working backwards from the syringe you actually own — the diluent guide walks through that in general, and the calculator will flag a draw that exceeds your syringe rather than quietly returning it. Reconstituted solution does not keep indefinitely either; the storage guide covers why potency loss is invisible when it happens.

There is no published half-life to reason from

The library entry records TB-500's half-life as not characterised, and that is a deliberate statement rather than a missing field. The 1.5–3 hour figures in circulation trace to vendor and aggregator pages, not to primary literature. Every completed human trial used pharmaceutical-grade full-length thymosin beta-4, a different molecule from the fragment sold as TB-500, and none reports an elimination half-life for the fragment.

With no published half-life for the compound actually being sold, there is no pharmacokinetic figure to check any claim about timing against. “Widely repeated” is not “established”.

TB-500 is not thymosin beta-4

Nearly all of the research people cite for TB-500 is research on thymosin beta-4 (Tβ4), the full 43-amino-acid protein. TB-500 as sold is generally a short synthetic fragment of it. These are related but not interchangeable, and the substitution happens silently in almost every write-up.

Tβ4 itself has a genuine clinical research history — it has been through company-run human trials for indications including dry eye and wound healing, which is considerably more than most compounds in this library can claim. Whether findings for the full protein transfer to a fragment is a separate question, and one the marketing does not raise. Separately, do not confuse TB-500 with thymosin alpha-1: the shared “thymosin” name describes an origin, not a family resemblance, and thymosin alpha-1 is an unrelated immune peptide with its own approvals in some countries.

What to record

Record the dose in micrograms even when your instructions say milligrams — a log that mixes “mg” entries with “mcg” entries invites exactly the comparison error this article is about. Record the concentration, the unit count, the site, the reconstitution date, and how much is left in the vial.

An entry with the microgram amount, the unit count, “at 5 mg/mL”, “left delt” and “vial opened 14 Jul” is still interpretable in six weeks. “40 units” on its own is not, because the next vial will be mixed differently.