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 the habits built on the first one are actively dangerous applied to the second. BPC-157 protocols are written in micrograms. TB-500 protocols are written in milligrams. Same syringe, same arithmetic, numbers a thousand times apart.

The trap, stated plainly

A commonly circulated BPC-157 dose is 200 mcg. A commonly circulated TB-500 dose is 2000 mcg — which almost nobody writes that way. It gets written as “2 mg”. If you have internalised “my dose is a couple of hundred” from one compound and you type 2 into a field expecting micrograms, you have asked for a thousandth of the intended dose. Type 2000 into a field expecting milligrams and you have asked for four hundred times the entire vial.

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.

The vial sizes you'll meet

TB-500 is typically supplied as 2 mg, 5 mg, 10 mg of lyophilised powder. Unlike BPC-157, the dose is a substantial fraction of the vial, so the draw volumes are large and the number of doses per vial is small.

5 mg vial, 2 mL of bacteriostatic water

• Concentration: 5 mg ÷ 2 mL = 2.5 mg/mL
• A 2000 mcg (2 mg) dose = 2 ÷ 2.5 = 0.8 mL = 80 units
• Doses in the vial: 5 ÷ 2 = 2 whole doses

Eighty units is most of a 1 mL syringe. It will not fit a 0.5 mL syringe at all, and a 0.3 mL syringe is out of the question. This is the first structural difference from BPC-157: with TB-500 the syringe size is a real constraint rather than a preference.

10 mg vial, 2 mL of bacteriostatic water

• Concentration: 10 mg ÷ 2 mL = 5 mg/mL
• A 2000 mcg dose = 2 ÷ 5 = 0.4 mL = 40 units
• Doses in the vial: 10 ÷ 2 = 5

Forty units on a 1 mL syringe is an unambiguous mark to read. Five doses at a twice-weekly cadence is about two and a half weeks of vial, which finishes inside the ~30 day window usually cited after reconstitution — the opposite of the situation with a microgram-dosed compound like BPC-157, where a 40-dose vial taken once daily outlasts its own solution by more than a week. The storage guide covers why that kind of potency loss is invisible when it does happen.

2 mg vial, 1 mL of bacteriostatic water

• Concentration: 2 mg ÷ 1 mL = 2 mg/mL
• A 2000 mcg dose = 2 ÷ 2 = 1.0 mL = 100 units
• Doses in the vial: 1

The entire vial is one dose, and it fills a 1 mL syringe to the line. There is nothing wrong with this arithmetically, but there is no margin in it: any loss in the needle or the vial means the dose is short, and a single-dose vial makes the whole reconstitution question moot.

The comparison worth internalising

Note the last row against the fourth: the same 10 mg vial can produce a comfortable 40-unit draw or a full-syringe 100-unit draw, purely from how much water went in. With BPC-157 the diluent choice moves you between “slightly fiddly” and “comfortable”. With TB-500 it moves you between “fits” and “does not fit”. Decide the diluent 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.

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.

That matters for the twice weekly during a loading phase schedule circulating protocols specify. With no published half-life for the compound actually being sold, that schedule cannot be derived from pharmacokinetics in either direction — it is convention. It may well be a sensible one, and tissue-level effects genuinely can outlast plasma presence, but “widely repeated” is not “established”, and there is no number here to check it against.

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 protocol 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

Because TB-500 doses are a large fraction of the vial, the log entry that matters most is how many doses are actually left. Record the dose in micrograms even when the protocol says milligrams — a log that reads “2 mg” alongside a BPC-157 entry reading “250 mcg” invites exactly the comparison error this article is about. Record the concentration, the unit count, the site, and the reconstitution date.

“2000 mcg — 40 u at 5 mg/mL, left delt, vial opened 14 Jul” is still interpretable in six weeks. “40 units” is not, because the next vial will be mixed differently.