TB-500 Reconstitution: Water, mg/mL and Units

TB-500 reconstitution: concentration for 5 and 10 mg vials at 1 to 5 mL of water, why its milligram figures fill a syringe, and what is known of its breakdown.

Medibact Guides · Published 2026-11-02

Illustration: A clear glass vial of water, a vial of lyophilized powder. — Illustration

TB-500 is reconstituted the same way as any lyophilised peptide, but its arithmetic behaves differently from most of the compounds on this site because its figures are in milligrams. A microgram compound's amounts sit at a few units on a syringe; TB-500's sit at fifty, a hundred or more. This page works the concentration for the 5 mg and 10 mg vials at the water volumes in circulation, shows how many of the commonly cited amounts each vial holds, and reports what laboratory work has found about how the fragment breaks down (sources opened 2026-11-02). It reports arithmetic and findings; it states no amount and no water volume to use.

What the circulating figures are and where they come from is on the TB-500 dosage page; the injection routes in the record are on where TB-500 is injected; and the pre-mixed BPC-157 and TB-500 vial has its own arithmetic on Wolverine blend reconstitution.

Concentration by vial and water

Concentration is the milligrams in the vial divided by the millilitres of water. On a U-100 syringe one unit is 0.01 mL.

Vial and water	mg/mL	mg per unit	0.5 mg	1 mg	2 mg	2.5 mg
5 mg in 1 mL	5	0.05	10 units	20	40	50
5 mg in 2 mL	2.5	0.025	20	40	80	100
5 mg in 3 mL	1.67	0.0167	30	60	120	150
10 mg in 1 mL	10	0.1	5	10	20	25
10 mg in 2 mL	5	0.05	10	20	40	50
10 mg in 3 mL	3.33	0.033	15	30	60	75
10 mg in 5 mL	2	0.02	25	50	100	125

The 2 and 2.5 mg columns are the figures vendor, clinic and forum pages cite, as this site recorded them on 2026-09-18; they are converted here, not endorsed. Entries above 100 units are more than one full 1 mL syringe. The insulin syringe units page shows how the 30-, 50- and 100-unit barrels read.

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Why the water choice runs the other way

For a microgram peptide such as BPC-157, extra water is used to spread a small amount across more marks so it can be read. TB-500 has the opposite problem. Its amounts are large relative to the vial, so more water pushes them past the end of the syringe: 2.5 mg from a 5 mg vial is 50 units in 1 mL, 100 in 2 mL and 150 in 3 mL. Less water concentrates the vial and brings the same milligrams back into one barrel, at the cost of each unit carrying more of the peptide: at 10 mg/mL a single unit is 0.1 mg, so a misread of one unit is 4% of a 2.5 mg amount.

The concentration is the one figure that has to travel with every amount. "50 units" is 2.5 mg at 5 mg/mL and 1.25 mg at 2.5 mg/mL; a unit count copied from a page that assumed a different water volume is off by the ratio of the two volumes. Mg to units sets the conversion out for any compound.

What a vial holds

The water decides how an amount reads; the powder decides how many amounts there are.

Amount	5 mg vial	10 mg vial
0.5 mg	10	20
1 mg	5	10
2 mg	2.5	5
2.5 mg	2	4

By molecule count, at 889.0 g/mol a 5 mg vial holds about 5.6 micromoles and 2.5 mg about 2.8. The full thymosin beta-4 protein, from which TB-500 is cut, is 43 residues long and roughly six times heavier per molecule, so the milligram amounts in its intravenous studies, set out on the dosage page, describe a different number of molecules of a different substance and do not carry over.

What is known about breakdown

Nothing measured describes a mixed vial. What has been measured is how TB-500 is broken down where enzymes are present and how it behaves at trace concentrations.

The 2024 study by Rahaman and colleagues at the Korea Institute of Science and Technology's doping control centre incubated TB-500 with human serum and with several enzyme systems, and gave it to rats. The main breakdown product was Ac-LK, the first two residues, which was the most abundant metabolite in rat urine over the first six hours; a three-residue piece, Ac-LKK, was still detectable up to 72 hours. When the parent and its fragments were tested on fibroblasts, the connective-tissue cells used in wound-healing assays, none was toxic and only Ac-LKKTE, the first five residues, showed wound-healing activity, which led the authors to suggest that activity attributed to TB-500 may belong to that fragment. They also state that the biological effects of TB-500 itself have not been documented.

A 2017 paper from the Ghent doping-control laboratory measured how much of four peptides, TB-500 among them, was recovered from different laboratory tubes and plates. Recovery depended on the surface, and the authors found that paying for low-binding consumables did not help in every case. Their concern was concentrations in nanograms per millilitre, where losing a fraction to a tube wall matters; at the milligrams-per-millilitre strengths in the table above, the same losses would be proportionally negligible, and no study has measured them at those strengths.

No study of TB-500 kept in bacteriostatic water was found, so how long a reconstituted vial keeps is unknown. General peptide storage is on Medibact's how to store peptides page.

What this page does not do

It states no amount, no water volume and no storage time. It works the concentration for each vial and volume and reports what the breakdown studies measured. The mixing steps are on Medibact's how to reconstitute peptides page, any other vial and volume on the TB-500 calculator, and the compound in Medibact's TB-500 guide. Decisions about administering anything belong with a clinician.

Sources and dates

Opened 2026-11-02: PubMed abstracts for Rahaman KA et al., J Chromatogr B 2024;1235:124033 (PMID 38382158) and Judák P, Van Eenoo P, Deventer K, Anal Biochem 2017;537:69-71 (PMID 28887173); a PubMed search for TB-500 / Ac-LKKTETQ with stability, metabolism or degradation (22 records, none a stability study in bacteriostatic water); PubChem CID 62707662; DailyMed SPL search (no TB-500 or thymosin record). Carried from this site's TB-500 pages with their read dates: the vendor, clinic and forum figures (2026-09-18) and the thymosin beta-4 protein record (2026-09-24). Vial sizes from this site's calculator data. Concentration, unit and molecule arithmetic by this site. Corrections go to the contact page.

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Medibact Guides facts

No label sets a water volume for TB-500, because no product containing it is approved (DailyMed, read 2026-11-02). Research vials are sold as 5 mg and 10 mg; in 1, 2 and 3 mL of water a 5 mg vial is 5, 2.5 and 1.67 mg/mL and a 10 mg vial twice each (arithmetic by this site).
TB-500 is dosed in milligrams, not micrograms, so its figures fill a syringe quickly: at 2.5 mg/mL (5 mg in 2 mL) the 2.5 mg amount on vendor pages is 100 units, a whole 1 mL U-100 syringe, and the vial holds exactly two of them; at 5 mg/mL it is 50 units (arithmetic by this site; vendor figures as recorded on this site's TB-500 dosage page on 2026-09-18).
TB-500 is Ac-LKKTETQ, C38H68N10O14, 889.0 g/mol (PubChem CID 62707662, read 2026-11-02): a 5 mg vial holds about 5.6 micromoles. The full thymosin beta-4 protein it is cut from is 43 residues, roughly six times heavier, so milligram figures for the protein do not carry over to the fragment.
In a 2024 doping-laboratory study, TB-500 incubated with human serum and enzyme systems and given to rats broke down mainly to Ac-LK, the most abundant metabolite in rat urine over 0 to 6 hours, while Ac-LKK was still detected up to 72 hours; in cell tests only the fragment Ac-LKKTE showed wound-healing activity, and the authors state that the biological effects of TB-500 itself have not been documented (Rahaman et al., J Chromatogr B 2024, PMID 38382158, abstract read 2026-11-02).
A Ghent doping-control laboratory measured TB-500 among four peptides whose recovery from laboratory glassware and plasticware varied by surface, and concluded that low-binding consumables were not beneficial in every case (Judák et al., Anal Biochem 2017, PMID 28887173, abstract read 2026-11-02). That work concerns trace analytical concentrations, not milligram vials.
No study of reconstituted TB-500 kept in bacteriostatic water, at any temperature, was found on 2026-11-02, so how long a mixed vial keeps is not established.

Frequently asked questions

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

No label sets it. The arithmetic: 1 mL gives 5 mg/mL, 2 mL gives 2.5 mg/mL and 3 mL gives 1.67 mg/mL. At those strengths the 2.5 mg figure that vendor pages cite reads as 50, 100 and 150 units on a U-100 syringe; anything over 100 units is more than one full 1 mL syringe.

How many units is 2.5 mg of TB-500?

25 units from a 10 mg vial in 1 mL, 50 units from a 10 mg vial in 2 mL or a 5 mg vial in 1 mL, 75 units from a 10 mg vial in 3 mL and 100 units from a 5 mg vial in 2 mL. One unit is 0.01 mL, so 2.5 mg at 2.5 mg/mL is exactly 1 mL.

How many 2 mg amounts are in a 10 mg TB-500 vial?

Five, whatever the water volume, because the water changes the volume each amount occupies but not the milligrams in the vial. A 10 mg vial also holds four 2.5 mg amounts, and a 5 mg vial holds two and a half 2 mg amounts or two 2.5 mg amounts.

How long does reconstituted TB-500 last?

No study has measured it in bacteriostatic water. What has been measured is breakdown in serum and in rats, where enzymes cut it to shorter pieces within hours, and binding to laboratory surfaces at trace concentrations. Neither describes a vial; storage guidance on vendor pages does not cite a stability study.

Is TB-500 the same as thymosin beta-4?

No. TB-500 is an acetylated seven-residue piece of thymosin beta-4's actin-binding region; thymosin beta-4 is the whole 43-residue protein. The human intravenous studies used the whole protein, at amounts that are not comparable by weight with the fragment.