How Long Does TB-500 Last? Storage Before and After Mixing

Lyophilised TB-500 keeps at 2 to 8 °C for the weeks a vial is in use and at minus 20 °C for months. Mixed with bacteriostatic water, it lasts 8 to 12 weeks in the fridge under Vistara Labs’ handling guidance, with quality slowly fading from around week 6 to 8. A mixed vial stays cold, dark and unfrozen. No published stability study covers TB-500 in solution over weeks, so that window is the general peptide guidance; what the literature does cover is what TB-500 is, how it breaks down, and why that differs from full-length thymosin beta-4.

Findings

• The peptide identified in TB-500 is Ac-LKKTETQ, the N-terminally acetylated 17 to 23 fragment of thymosin beta-4, confirmed by high-resolution mass spectrometry (2012).
• Full-length thymosin beta-4 has a methionine at position 6 that oxidises to thymosin beta-4 sulfoxide; the seven-residue fragment does not contain that position (1995, 1999).
• In human serum and enzyme systems, TB-500 is cut into shorter acetylated pieces such as Ac-LK and Ac-LKK (2024).
• TB-500 was one of four peptides chosen for a 2017 study of losses to glass and plastic surfaces at low concentrations.

What is in a TB-500 vial?

Thymosin beta-4 is a 43-amino-acid protein. TB-500 is not the whole protein: when a doping laboratory analysed a TB-500 product, the peptide it identified was Ac-LKKTETQ, residues 17 to 23 of thymosin beta-4 with an acetyl group added to the N-terminus, and it synthesised the same peptide to confirm the match (Esposito et al., Drug Test Anal, 2012). An equine study the same year described the key ingredient of the veterinary preparation in the same terms (Ho et al., J Chromatogr A, 2012). The full distinction is in TB-500 vs thymosin beta-4.

That matters for storage. Full-length thymosin beta-4 carries a methionine at position 6, and oxidation there produces thymosin beta-4 sulfoxide, which binds actin less well (Huff et al., Eur J Biochem, 1995) and behaves as a different signalling molecule (Young et al., Nat Med, 1999). The 17 to 23 fragment has no methionine or cysteine, so that oxidation route does not apply to it.

How does TB-500 break down?

The best-mapped breakdown is enzymatic. A 2024 study incubated TB-500 in human serum and several enzyme systems and tracked the products: Ac-LK was the main metabolite in treated rats over the first 6 hours, and Ac-LKK persisted for up to 72 hours (Rahaman et al., J Chromatogr B, 2024). Those are the cuts peptidases make in biological fluid. A sterile vial mixed with bacteriostatic water, swabbed before every access, keeps those enzymes out, which is a large part of what the fridge window depends on.

The second loss route is physical. TB-500 was one of four doping-relevant peptides chosen for a study of recovery from different glassware and plasticware, which found that low-bind consumables were not always the better choice and that containers should be matched to each peptide’s chemistry (Judák et al., Anal Biochem, 2017). That work was done at nanogram concentrations; a research vial holds milligrams, where surface losses are proportionally far smaller.

How long does TB-500 powder last?

Sealed and dry, TB-500 keeps at 2 to 8 °C for the weeks a vial is in use, and at minus 20 °C for longer holding. A cold vial reaches room temperature before the stopper is pierced, so condensation does not settle on the powder. Days at room temperature in transit do not harm it.

How long does TB-500 last after mixing?

Condition	TB-500
Lyophilised, sealed, 2 to 8 °C	The weeks the vial is in use
Lyophilised, sealed, minus 20 °C	Months
Mixed with bacteriostatic water, 2 to 8 °C	8 to 12 weeks, fading from around week 6 to 8
Mixed, room temperature	Not stored this way
Mixed, frozen for repeat access	No; single-use aliquots frozen once only

The same window applies to the BPC-157 + TB-500 blend, whose other component is covered in how long BPC-157 lasts. The USP General Chapter 797 figure of 28 days for a preserved multi-dose container is a sterility convention, separate from the peptide’s own stability. Mixing volumes and the peptide calculator are covered in the reconstitution guide; a 10 mg TB-500 vial takes the same arithmetic as a 10 mg BPC-157 vial on the BPC-157 reconstitution page.

How can you tell TB-500 has degraded?

Mixed TB-500 is clear and colourless, and so are the short acetylated fragments it breaks into, so appearance cannot confirm strength; the mixing date and cold storage carry that weight. Discard the solution if it shows:

• Persistent cloudiness after the first 10 to 15 minutes.
• Strands, flakes or particles, or a film on the glass.
• A yellow or brown tint.
• A history of freezing and thawing, or a night out of the fridge.

More on haze and gel: why peptides gel or go cloudy.

Travelling with TB-500

Sealed vials ride out a few days at ambient temperature away from direct heat. A mixed vial needs to stay cold, which the peptide travel case is built for. Orders ship from within Canada by Canada Post Xpresspost.

What about the TB-500 nasal spray?

The TB-500 Nasal Spray and the BPC-157 + TB-500 Nasal Spray come ready-mixed in a sealed metered pump (0.175 mL per press). The peptide is already in solution, so the bottle lives upright in the fridge. See how to store a peptide nasal spray.

Frequently asked questions

How long does TB-500 last in the fridge?

Mixed with bacteriostatic water and kept at 2 to 8 °C in the dark, TB-500 lasts 8 to 12 weeks under Vistara Labs’ handling guidance, with quality slowly fading from around week 6 to 8. Sealed powder keeps in the fridge for the weeks it is in use.

How long does TB-500 last at room temperature?

Sealed lyophilised TB-500 tolerates a few days at room temperature, such as shipping. A mixed vial is not kept at room temperature; it returns to the fridge after each access.

Can you freeze TB-500?

Sealed powder can be held at minus 20 °C for months. A mixed vial that will be opened again is not frozen, because freeze-thaw cycles aggregate peptides in solution; laboratories freeze single-use aliquots once instead.

Does TB-500 go bad?

Yes, slowly, and faster when warm. The Ac-LKKTETQ fragment lacks the methionine that oxidises in full-length thymosin beta-4, but in biological fluid it is cut into shorter pieces such as Ac-LK, which is why mixed vials are kept sterile and cold.

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

Not quite. Full-length thymosin beta-4 has a methionine at position 6 that oxidises to a sulfoxide; the seven-residue TB-500 fragment does not contain it. Both are stored cold, dark and dry.

Handling windows: Vistara Labs, October 2026. Sources: Esposito S et al. Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential. Drug Test Anal. 2012. PMID 22962027. Ho EN et al. Doping control analysis of TB-500, a synthetic version of an active region of thymosin beta4, in equine urine and plasma by liquid chromatography-mass spectrometry. J Chromatogr A. 2012. PMID 23084823. Huff T, Zerzawy D, Hannappel E. Interactions of beta-thymosins, thymosin beta 4-sulfoxide, and N-terminally truncated thymosin beta 4 with actin. Eur J Biochem. 1995. PMID 7607239. Young JD et al. Thymosin beta 4 sulfoxide is an anti-inflammatory agent generated by monocytes in the presence of glucocorticoids. Nat Med. 1999. PMID 10581087. Rahaman KA et al. Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS. J Chromatogr B. 2024. PMID 38382158. Judák P, Van Eenoo P, Deventer K. Adsorption effects of the doping relevant peptides Insulin Lispro, Synachten, TB-500 and GHRP 5. Anal Biochem. 2017. PMID 28887173. USP General Chapter 797, beyond-use dating.

More on this: How Long Do Peptides Last After Mixing?, TB-500 and thymosin beta-4: the repair research and Buy TB-500 in Canada.