How to read a BPC-157 + TB-500 blend COA: two identities, two amounts, and the thymosin beta-4 line, worked through on lot RN-2610-BPCTB

What a BPC-157 + TB-500 blend COA has to show#

A BPC-157 + TB-500 blend is two separate synthetic peptides in one lyophilized vial, labelled 5 mg + 5 mg for a 10 mg total. Its Certificate of Analysis has to establish, for each peptide independently, that it is present (identity), how much of it there is (content), and how clean the mixture is overall (purity). A report that confirms only "identity" for the vial, or gives only a total, cannot tell you whether both peptides are there in the amounts the label states.

This guide explains what each component is, what a two-peptide report must show, and then reads Renuvia's published report for lot RN-2610-BPCTB, including a line that readers often ask about: the report also lists thymosin beta-4 at 0.23 mg. It ends with a checklist for any two-peptide blend COA. The general anatomy of a report is covered in how to read a Certificate of Analysis, and the two analytical techniques in HPLC and mass spectrometry explained.

BPC-157 and TB-500: sequence and molecular weight#

Mass-spectrometry identity is a comparison between a measured mass and the mass a molecule should have, so the expected values come first. Both peptides were the subject of FDA evaluations prepared for the agency's Pharmacy Compounding Advisory Committee meeting of July 23-24, 2026, which set out their identity data.^[2][3]

FDA's TB-500 document describes it as a seven-amino-acid synthetic fragment of thymosin beta-4 from amino acids 17 to 23, and adds in a footnote that thymosin beta-4 and TB-500 are not the same substance.^[3] That distinction is the key to reading the blend report below.

TB-500 and thymosin beta-4: a fragment and its parent protein#

Thymosin beta-4 is a naturally occurring protein. The human sequence in UniProt (P62328) is 44 residues including the initiator methionine: MSDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES.^[5] Counting from the serine that follows the methionine, residues 17 to 23 read LKKTETQ, the same seven residues as TB-500. The fragment is a small piece of the protein; the protein is roughly five and a half times heavier.

The two are easy to tell apart by mass. Esposito and colleagues, analyzing a product sold as TB-500 for an anti-doping laboratory, gave a theoretical mass of 888.4911 for the acetylated fragment Ac-LKKTETQ and a molecular weight of 4963.4642 for endogenous thymosin beta-4. They identified the fragment in that product by high-resolution LC-MS, observing ions at m/z 445.2532 ([M+2H]2+) and 889.4988 ([M+H]+), and reported that the product they tested did not contain the full-length protein.^[4] In other words, "TB-500" and "thymosin beta-4" are separate analytical targets, and a laboratory can look for and report each one.

What a two-peptide blend COA must show#

• Identity for each peptide. The identity line should name both, and the mass section should show labelled ions for each. FDA's 2024 Q2(R2) guidance describes specificity as the extent to which other substances interfere and expects an assay to discriminate the analyte from them;^[6] in a blend, each peptide is the "other substance" for the other.
• Content for each peptide in milligrams. A 5 mg + 5 mg label is two claims. Only a per-peptide figure lets you check both, and the ratio between them.
• A sum you can compare with the label. Add the two (and anything else the report quantifies) and compare with 10 mg.
• A purity figure read for what it is. HPLC-UV purity is the share of ultraviolet signal belonging to the named peaks. Peptides absorb differently: Kuipers and Gruppen measured tryptophan at about 30 times a peptide bond at 214 nm and phenylalanine, tyrosine and histidine at about six times.^[7] Peak size is therefore not a measure of milligrams, and purity says nothing about the ratio.
• Anything else detected, named. If the laboratory finds and identifies another peptide, a good report says so rather than folding it into an unexplained impurity figure.

Worked example: BPC-157 + TB-500 lot RN-2610-BPCTB#

Renuvia's report for this lot is published in the COA library and linked from the BPC-157 + TB-500 blend product page.^[1] It was issued by Freedom Diagnostics Testing, which received the sample on 10/29/2026 and reported on 10/31/2026, using HPLC with UV detection coupled with mass spectrometry (LC-MS).

The header#

The client is Renuvia Labs; the laboratory accession number is 2610291408 and the search code Renu2610291408. The laboratory's Lot field reads "Black Cap", the description of the vial submitted, rather than Renuvia's lot code; the COA library entry links this accession number to lot RN-2610-BPCTB. The accession number is what to quote to the laboratory, as described in how to verify a COA is genuine. The product line reads "BPC-157 + TB-500 Blend 10mg" and the appearance line "White Lyophilized Powder".

Identity: three molecules named#

The identity line reads "TB-500/Thymosin Beta-4/BPC-157", and the Mass Confirmation section has a panel for each. Comparing the labelled ions with the reference values:

The agreement is within a few tenths of a mass unit for each, which is typical for a routine instrument reporting to one decimal place. Large proteins carry many charges in electrospray, which is why thymosin beta-4 appears at m/z 828 rather than near 4,963.

Content: 5.60 mg and 5.01 mg against 5 mg + 5 mg#

Both labelled peptides are present in separately reported amounts. TB-500 is within a fraction of a percent of its label figure; BPC-157 is above it. A measured figure above the label has several ordinary contributors that a report rarely distinguishes: fill tolerance, measurement uncertainty (the Eurachem/CITAC guide describes how laboratories estimate it^[8]), and the basis on which content is calculated, for example free peptide versus salt, which the TFA and counter-ion guide explains. Method validation guidance gives 80% to 120% of declared content as the reportable range an assay is built to cover,^[6] which is a design range for the method, not a specification for the product. The report does not say which factor applies here.

Purity: 99.26%#

The reported HPLC-UV purity is 99.26%. The chromatogram shows a TB-500 peak, a larger BPC-157 peak, and a much smaller peak labelled thymosin beta-4 just after BPC-157. The report does not state whether the thymosin beta-4 peak is counted inside the 99.26% figure, as an identified component, or outside it. If that distinction matters to a study, it is a question for the laboratory, quoting the accession number.

Why the report lists thymosin beta-4 at 0.23 mg#

What the report says is limited and specific: the laboratory identified thymosin beta-4 by mass, saw a small chromatographic peak it assigned to it, and quantified it at 0.23 mg in the vial. That is about 2% of the 10.84 mg total the report quantifies across all three. The report does not say where it came from, and this guide does not claim to know.

Two things can be said from the chemistry and the sources. First, the thymosin beta-4 line is not a second name for TB-500: the two have different masses (888.4911 versus 4963.4642), the report gives them separate ions, a separate peak and a separate milligram figure, and FDA states they are not the same substance.^[3][4] Second, it cannot be a breakdown product of TB-500. A 43-residue protein cannot form from a seven-residue fragment; breakdown runs the other way.

Beyond that, the honest position is that the report shows a small amount of a third, related peptide and leaves the reason open. A researcher for whom the presence of full-length thymosin beta-4 matters, for instance because an assay could respond to it, has three reasonable steps: ask the supplier for the synthesis or raw-material documentation for the TB-500 used, ask the laboratory to confirm the assignment and how the peak was quantified, and check whether later lots report it at all. The COA library shows each lot's report as issued, so a change from lot to lot would be visible there.

Checklist for any two-peptide blend COA#

1. The product line names the blend and its strength, and the report is for the blend, not a single-peptide report shown in its place.
2. Both peptides are named in the identity line, with labelled mass-spectrometry ions for each.
3. The ions match the expected masses (for this blend, about 445.3 and 889.5 for TB-500 and about 710.4 for BPC-157).
4. Each peptide has its own milligram figure, which you can compare with its half of the label.
5. The two figures add up to a total within a few percent of the label, and the ratio between them is close to what the label states.
6. Any other molecule the laboratory found is named, with its own figure, and you know whether it is inside or outside the purity number.
7. The purity figure is read as a share of UV signal in the named peaks, not as a statement about amounts or ratio.
8. The header carries a laboratory accession number and dates, and you know how the report is tied to the lot on your vial.
9. You know what is not reported (counter-ion, water, endotoxin) and whether your work needs it.

The PDF for lot RN-2610-BPCTB is linked from its entry in the COA library, so every figure in this guide can be checked against the original. Lots whose report has not yet been issued show as pending, with no figure from any other source.