Where to buy TB-500 Peptide: sizes, price per mg and how to verify the lot

What "tb-500 peptide" names, and what it does not

TB-500 is a seven-residue synthetic peptide, Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln, written Ac-LKKTETQ in one-letter code. It is a copy of residues 17 to 23 of thymosin beta-4, the region of that protein described in the actin-binding literature cited below, with an acetyl group added to the N-terminus. The listings that say TB500, TB 500 or tb500 peptide mean this fragment. The listings that say "thymosin beta-4" and then sell a 5 mg vial for the price of a fragment usually mean it too, and that is the confusion this page exists to clear up.

Thymosin beta-4 itself is a 43-residue protein with a molecular weight of about 4,963 Da. The fragment is 889 Da. They are different molecules by a factor of five in mass, different in synthesis cost by more than that, and different in what a certificate has to show. A seller that prints "thymosin beta-4" on the label, "TB-500" in the listing and a certificate showing a 4,963 Da mass has either shipped the protein under a fragment's name or attached somebody else's certificate; a seller whose certificate shows 889 Da has shipped the fragment, and should call it that.

The acetyl group is the other detail that decides identity. Un-acetylated LKKTETQ weighs 846.5 Da, 42 Da less than TB-500, and it is a different compound with a different retention time. A certificate whose observed mass is around 846 has identified the wrong molecule, and a purity figure taken from that chromatogram describes the wrong molecule too. The research record on the fragment is thin and almost entirely cell and animal work; this page describes the material, not any use of it.

The reference point for identity is public. PubChem lists TB-500 as CID 62707662 with molecular formula C38H68N10O14, an average molecular weight of 889 Da and a monoisotopic mass of 888.492 Da. Those are the numbers a mass spectrometer is checked against, and the number a certificate must print beside the observed mass.

In plain terms: A man-made peptide matching a section of thymosin beta-4. No approved product, no official standard, and very little human research. The section-versus-whole-protein distinction gets blurred commercially, so check which one a certificate actually names.

TB-500 for sale: sizes and price per mg

LabFirst lists TB-500 in 2 sizes (5mg, 10mg) from $54 to $60, priced per vial with the per-mg figure beside it so sizes can be compared without arithmetic. Per mg, the 10mg vial is the cheapest at $6 and the 5mg the dearest at $10.80, which is the usual shape: the vial, stopper, seal, fill and laboratory run cost the same whatever mass goes in.

The volume tiers are per size, not per basket: ten vials of one size take 10% off that line and twenty take 15%, and mixed sizes do not combine. Shipping is a flat $15 on orders under $200 and free from $200, within the United States only, with same-day dispatch on orders placed before 12 PM Pacific on a business day. The cost per mg tool runs the same comparison across any two listings, ours or anyone else's.

A seven-residue synthesis is inexpensive, so TB-500 is priced by the vial, the fill and the test rather than by the chemistry, and the per-milligram figure falls sharply from the 5 mg to the 10 mg vial. The signal to watch is the gap between what a seller charges for TB-500 and what it charges for "thymosin beta-4". If the two are priced the same per milligram, the seller is selling the fragment under both names; a 43-residue protein cannot be made for the price of a 7-mer.

The other thing to price is the blend. TB-500 is a component of the BPC 157 + TB-500 blend and of GLOW and KLOW, and buying it inside a blend is only cheaper per milligram if the certificate for the blend reports each component's content separately. A blend certificate that reports one purity for the whole vial gives no per-milligram figure for TB-500 at all, so there is nothing to compare. Where a laboratory needs a known quantity of the fragment, the single-compound vial is the one that can be documented.

The certificate a TB-500 lot must carry

Three tests answer three different questions, and a certificate of analysis for TB-500 is only complete when it carries all three for the exact lot on the vial. Identity is settled by mass spectrometry, and the number to look for on a TB-500 certificate is 888.492 Da monoisotopic (or 889 Da average, if the laboratory reports the deconvoluted average mass). The observed mass should sit within the instrument's stated tolerance of that figure, and the certificate should print both the theoretical and the observed value, not just a tick.

Purity is a separate question, answered by HPLC: how much of what came off the column was the compound. The figure is only interpretable with its method beside it (column, gradient, detection wavelength) and a date, which is what ICH Q2(R2) means when it asks that an analytical procedure be shown fit for its purpose. A percentage with no method and no date is a number somebody typed, and a certificate that carries every test but for a different lot number than the vial is the most common failure of all and the easiest to catch. Net content is the third test and the one most often missing: the milligrams of TB-500 actually in the vial, measured, against the size printed on the label.

The number to find first on a TB-500 certificate is the observed mass against 888.492 Da monoisotopic (889.0 Da average, formula C38H68N10O14). In electrospray the singly charged ion sits near m/z 889.5 and the doubly charged near m/z 445.3, and a laboratory that deconvolutes the spectrum prints a value within a fraction of a dalton of 888.5. The two wrong answers are easy to spot: a mass near 846 is the un-acetylated fragment, and a mass near 4,963 is the whole protein. Either one means the vial does not contain what the listing sold.

Purity by HPLC follows. Seven residues with two lysines and two threonines give a peptide that runs early on a reversed-phase column, and the common impurities are the des-acetyl form and a deletion missing one threonine; both sit close to the main peak, so the chromatogram should be shown, with its gradient and wavelength, not summarised as a percentage. Net content closes the record. TB-500 is normally supplied as the acetate salt, and a laboratory that reports net peptide content by amino acid analysis or quantitative HPLC against a standard tells you how many of the labelled milligrams are peptide. Without that line, a 10 mg label is a statement about the powder, not the peptide.

Where to buy TB-500: five checks before you order from anyone

Every seller of tb-500 peptide says "third-party tested". The phrase costs nothing. These five checks take about four minutes per listing and separate a tested lot from a tested-sounding one.

1. The lot on the vial is the lot on the certificate. Read the printed lot number, then open the certificate and match it. A certificate for "TB-500" with no lot, or a lot that does not match, describes some other vial.
2. The laboratory is named and has its own lookup. The report should come from a laboratory the seller does not own, with a search code you can enter on the laboratory's own site. LabFirst lots are tested by Freedom Diagnostics and looked up by accession number; anything that can only be verified on the seller's own page has not been verified.
3. The theoretical mass is printed, and it is the right one. For TB-500 that is 888.492 Da monoisotopic; a certificate that prints a different figure has either measured a different molecule or copied a template.
4. Purity has a method and a date. An HPLC percentage should name the method and the run date. A figure that reads "99%+" with neither, or one date reused across every product a seller lists, is decoration.
5. Net content is stated in milligrams. The label size is a claim; the certificate's net content is the measurement. If the certificate has no net content line, the purity figure describes the powder, not the vial, and the price per mg you calculated is fiction.

How listings for TB-500 specifically mislead:

• "Thymosin beta-4 5 mg" priced like a fragment. The protein is 43 residues and 4,963 Da; if the certificate shows 889 Da, the vial is TB-500, whatever the label says, and the listing should be read that way.
• A certificate with a mass near 846 Da. That is LKKTETQ without its acetyl group, a different compound; the purity percentage on the same page describes the wrong molecule.
• "TB-500 99.8%" from a chromatogram with no gradient, no wavelength and no date. The des-acetyl and deletion impurities run close to the main peak; a number without the trace cannot show they were resolved.
• Blend certificates (GLOW, KLOW, BPC 157 + TB-500) that report one purity for the vial. There is no TB-500 content figure in such a certificate, so the per-milligram price of the fragment inside it is unknowable.

How to verify a LabFirst TB-500 lot

The TB-500 sizes in stock today carry lots LF-2608-27 and PO-1001-TB10. Lot LF-2608-27 is at Freedom Diagnostics on accession FD-2026-05716 for identity, purity and net content. Until the report is attached the product page says "pending verification" against that lot and makes no purity claim; the price stands and the report goes live the day it arrives, on the page, at /coa/, and inside the receipt and packing slip for every order of that lot.

Verification runs through the laboratory, not through us. Open the certificate index, find the lot, and use the accession number on the Freedom Diagnostics lookup page; the report you see there is the laboratory's copy, not ours. Each lot also carries a Finnrick verify link, and every receipt and packing slip states that a customer may submit a sealed vial to Finnrick's free testing programme with the order as proof of purchase, so the brand's public record is built from vials we did not choose.

The product page reads the live stock feed on load (stock, lot and certificate state for every size), so what you see when you order is what ships. The lot is printed on the label and encoded in the QR patch on its right-hand side; scanning it opens that lot's record.

Storage and shipping for TB-500

TB-500 has no cysteine, no methionine and no tryptophan, so the usual chemical routes to degradation in a peptide (disulfide scrambling, oxidation, photodegradation) do not apply. Lyophilised and sealed at 2 to 8 C, out of light, it is among the more forgiving peptides in the catalogue. The glutamine at the C-terminus is the one residue to think about: glutamine can deamidate slowly in solution, which adds 1 Da and shifts retention time, so a prepared solution is dated, kept cold, and not trusted past the laboratory's own stability record. Water is the practical enemy of the sealed cake, as with every lyophilised peptide; open a vial once, for its purpose, and do not re-seal it for storage.

Orders ship within the United States, flat $15 under $200 and free above it, same day when placed before 12 PM Pacific on a business day, and the shipping page states the cutoff, the carriers and what is and is not promised.

The record a laboratory keeps on arrival is what makes the certificate usable later, and it is short:

• the lot number as printed on the vial, and the certificate's accession or search code beside it;
• the date received and the condition of the seal;
• the storage location and temperature it went into;
• the number of vials, and later the date each one was opened and by whom.

A TB-500 vial with that record behind it can be traced from the bench to the laboratory report in one step; without it, the certificate is a document about a vial that can no longer be identified.

Regulatory status, and what this page is not

No approved medicine contains TB-500 and no USP or Ph. Eur. monograph defines an acceptable lot. In September 2023 the FDA placed "Thymosin Beta-4, Fragment (LKKTETQ)" in Category 2 of its interim list of bulk drug substances nominated for compounding under section 503A, the category for substances it has identified as raising significant safety risks, which means licensed pharmacies may not compound with it. That listing is about compounding pharmacies and says nothing about laboratory material; it is quoted here because sellers routinely describe TB-500 as "pharmaceutical grade", and a substance on Category 2 with no monograph cannot be any grade at all.

FOR LABORATORY AND IN-VITRO RESEARCH USE ONLY. NOT FOR HUMAN OR ANIMAL CONSUMPTION. LabFirst sells TB-500 to laboratories and researchers as material for in-vitro work, gives no guidance on use, and ships only against that understanding. Nothing on this page or on the product page describes preparing or administering anything.

What is TB-500 studied for?

Published research on TB-500 investigates the areas below — which is a different question from what TB-500 will do for anyone, a claim about a living system that nothing on this site is sold for.

What it is. A man-made peptide matching a section of thymosin beta-4.

What the research looks at. Animal and cell-culture research on the cell skeleton and how cells move. Suppliers often blur TB-500 and full thymosin beta-4 together. They are not the same molecule, and this record is about the section.

How it is thought to work. Thymosin beta-4 is a protein that grabs hold of actin, the building material of a cell’s internal skeleton, and the section sold as TB-500 is its actin-grabbing part. The published work is about how actin behaves and how cells move in culture.

What is not established. No approved product, no official standard, and very little human research. The section-versus-whole-protein distinction gets blurred commercially, so check which one a certificate actually names.

The full record, including the certificate for the lot in stock, is on the TB-500 product page.

Common questions

Sources

• PubChem, TB-500, CID 62707662. Public record for the molecular formula (C38H68N10O14), average molecular weight (889 Da) and monoisotopic mass (888.492 Da) quoted here as the identity reference.
• Irobi, Aguda, Larsson, Guerin, Yin, Burtnick, Blanchoin and Robinson, Structural basis of actin sequestration by thymosin-β4, EMBO Journal 23(18):3599-3608 2004. Primary description of the compound in the literature; supports the class and naming stated here, not any use.
• Structural basis of thymosin-β4/profilin exchange leading to actin filament polymerization, PNAS 2014. Primary description of the compound in the literature; supports the class and naming stated here, not any use.
• Mapping the binding site of thymosin β4 on actin by competition with G-actin binding proteins, European Journal of Biochemistry 1998. Primary description of the compound in the literature; supports the class and naming stated here, not any use.
• Alliance for Pharmacy Compounding, 503A Categories Update, 29 September 2023 2023-09-29. Lists the substances the FDA moved to Category 2 on that date, including Thymosin Beta-4, Fragment (LKKTETQ).
• FDA, Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act. The FDA page that carries the current 503A category lists and the interim policy they sit under.
• ICH Q2(R2), Validation of Analytical Procedures (2023) 2023-11. Why a purity figure is only interpretable with its method, and what "fit for purpose" means for the HPLC and mass spectrometry results a certificate reports.
• Freedom Diagnostics, certificate lookup by accession number. The laboratory-side lookup a LabFirst lot is verified on; the report there is the laboratory copy, not ours.
• Finnrick, verify a vendor or lot. Independent verification page linked from every LabFirst lot; customers may submit sealed vials with their order as proof of purchase.