What is a certificate of analysis? It's a document reporting test results for one batch against its specifications—the standards that batch must meet. Often shortened to COA, it connects a material's name and lot number to the tests performed, their limits and their results.
That makes it useful paperwork. It doesn't make it a promise that a medicine will work, suit your health history or be free of every possible contaminant.
What is a certificate of analysis in pharmacy language?
The term has a real place in pharmacy compounding, which means combining or altering ingredients to prepare a medicine. It isn't just something sellers invented for their websites.
Section 503A(b)(1)(A) of the federal drug law, 21 U.S.C. 353a, requires bulk drug substances—the starting active ingredients—to come from an establishment registered with FDA. It also requires that they be “accompanied by valid certificates of analysis for each bulk drug substance.”
Those are two separate requirements. Registration identifies a manufacturer; the certificate reports on its material. Neither replaces the other conditions for compounding a prescription.
FDA's ICH Q7 guidance, section 11.4, describes the expected contents of an active pharmaceutical ingredient certificate. Active pharmaceutical ingredient, or API, means the ingredient intended to produce the medicine's effect. ICH is the international group that develops harmonized drug-quality guidance.
The guidance, marked “September 2016” and “Revision 1,” calls for the ingredient name, batch number, release date (when the batch cleared quality review), tests, acceptance limits and numerical results where appropriate. Certificates should be signed and dated by authorized quality personnel and identify the original manufacturer. Expiry or retest dates belong on the relevant paperwork when applicable.
Why the paperwork follows the batch
A lot number identifies a particular batch of material. Two batches with the same ingredient name can have different test results. A report about one doesn't establish the quality of the next.
For a BPC-157 prescription, the starting-ingredient certificate belongs to the pharmacy's sourcing records. The finished medicine has its own preparation and labeling steps. The pharmacy needs to connect those stages; a patient shouldn't have to reconstruct them from an online PDF.
That is why the document exists: to make a batch traceable and its test results reviewable. The name alone can't do that work.
How to read a COA: which question does each test answer?
A useful report shows both the result and the limit it was compared with. “Pass” without the test or its standard leaves too much unexplained.
The tests depend on the material and its intended use, so a report may not include every row below:
| COA entry | What it tells you |
|---|---|
| Identity | Whether the tested material matches the intended ingredient. Mass spectrometry measures molecular mass and can help check peptide structure. |
| HPLC purity | High-performance liquid chromatography separates components. “Area percent” is the target peak's share of the total signal detected by that method. |
| Assay | A measurement of how much active ingredient is present, often compared with a known reference material. |
| Related impurities | Measurements of unwanted molecules resembling the peptide, including manufacturing by-products or breakdown products. |
| Water and residual solvents | Measurements of moisture and chemicals left from making or processing the material. |
| Contamination testing | Separate checks for living microorganisms and bacterial material relevant to injectable preparations; chemical purity doesn't substitute for them. |
Peptides are chains of amino acids, the building blocks of proteins. Their chemistry can make a single test misleading.
In a 2015 study in the Journal of Pharmaceutical and Biomedical Analysis, one cyclic peptide—a chain joined into a ring—measured 99.5% by HPLC. A separate measurement found 80.3% peptide content. Water and a counterion, a charged component paired with the peptide, accounted for part of the difference. These were laboratory findings, not patient outcomes.
As of October 1, 2026, the day this article was written, a review published July 15, 2026 in the Journal of Pharmaceutical Investigation reinforces this distinction. It explains why peptide content must account for water, counterions and other non-peptide components. A large purity peak isn't a measurement of everything in the container.
For TB-500, the same reading questions apply: which material was tested, which method was used and what was actually measured? A percentage beside its name can't answer all three.
Sterility and endotoxin are different checks
Sterile means free of living microorganisms, such as bacteria and fungi. Endotoxin is material from certain bacteria that can remain after those bacteria are gone and can trigger reactions.
FDA's sterile-manufacturing guidance, section XI, identifies USP chapter <71>, Sterility Tests, as a principal source for sterility methods. USP stands for United States Pharmacopeia, which publishes medicine-quality standards. The guidance also explains why testing a small sample can't establish sterility throughout a whole batch by itself. Preparation controls matter too.
FDA's endotoxin guidance addresses the separate bacterial endotoxin test in USP chapter <85>. A COA that lists only identity and HPLC purity says nothing about either contamination test.
The distinction showed up in a 2024 Journal of Medical Internet Research test-purchase study. All three delivered online semaglutide samples had detectable endotoxin, although no living microorganisms were found at testing. That small study doesn't establish a failure rate for every seller or for prescribed pharmacy preparations.
The mistakes people make with a peptide COA
Reading “99% purity” as “safe.” The percentage describes one measurement. It doesn't establish the amount in a finished dose, the absence of contaminants or whether treatment fits a person.
Assuming a PDF means independent testing. Q7 permits manufacturer-issued certificates. Third-party peptide testing means a separate laboratory performed the work; the report needs to identify that laboratory and the sample it received. Independence alone doesn't establish how that sample relates to the supplied batch.
Trusting a document without a lot match. A mismatch leaves the connection unproven. A matching number is necessary for traceability, but a copied or fabricated document can still look convincing. Confirmation from the issuing laboratory helps establish authenticity; appearance alone doesn't.
Treating ingredient results as finished-medicine results. For tirzepatide, an ingredient COA and the pharmacy's finished-preparation records concern different stages. A raw-material purity figure doesn't establish the final strength, storage instructions or preparation quality.
As of October 1, 2026, the day this article was written, FDA explains that compounded drugs do not undergo its premarket review. Through Promise, tirzepatide is dispensed as a compounded medication, which is different from an FDA-approved product: the formulation offered here is not FDA-approved. A licensed provider may still prescribe — that decision is between you and your doctor.
Related terms in the prescription conversation
A bulk drug substance is the starting active ingredient. The 503A bulks list describes one ingredient pathway. A 503B outsourcing facility follows a separate compounding framework. None of those terms means the same thing as a batch's test report.
Our gray-market peptides guide covers the wider risks of buying without a prescription. Here, the useful distinction is simple: a certificate can answer questions about material; a named pharmacy and prescriber provide people who can answer questions about the prescription.
At Promise, a licensed provider reviews every request, and not everyone qualifies. The certificate is one part of the record behind a medicine. It doesn't replace the person responsible for your care.
