How to read a peptide pharmacy's certificate of analysis

That's not useless, but you're missing most of what the document is telling you.

A certificate of analysis — COA — is the lab document that accompanies a batch of compounded medication. It is produced by a third-party analytical laboratory that tests a sample from the batch against a set of specifications. The fact that a pharmacy provides a COA at all is meaningful; it means the batch was tested by someone independent of the people who made it. The fact that you have one is a baseline. The fact that you can read it is what actually protects you.

The document typically covers six areas. Each one is testing something different. Understanding which is which, and which ones are the most consequential for an injectable peptide, changes what you look for.

Identity comes first. This is the most foundational question: is this molecule actually what the label says it is? The most common method for answering that question is mass spectrometry — specifically a technique that measures the mass-to-charge ratio of a molecule and compares it against a reference standard. If the mass spectrum doesn't match the expected spectrum for, say, BPC-157, then nothing else on the COA matters. You don't have BPC-157. You have something else. Identity testing is the floor. It confirms you got the right molecule at all. People often skim past it because it usually passes, and because "mass spectrometry" sounds like jargon rather than a safety gate. It is a safety gate.

Assay is the next section and usually the one people land on first, because it gives you a percentage. Assay measures potency — specifically, the concentration of the active ingredient as a percentage of what the label claims. If your vial is labeled 5mg/mL and the assay comes back at 97% of label claim, that means you're getting approximately 4.85mg/mL. The typical specification for pharmaceutical-grade compounding is 90% to 110% of label claim — sometimes written as a tighter 95% to 105% depending on the compound and the pharmacy's internal standards. A result in that range means the concentration is close enough to the label that you can trust the dose. A result at 82% should make you ask questions. A result at 115% should make you ask different questions.

Purity and related substances is about contamination at the molecular level — not biological contamination, but chemical. During synthesis, peptides can form impurities: fragments of the intended molecule, side-chain products, related compounds that are structurally similar but not identical to what you want. These are called related substances. The COA will typically list the total related substances as a percentage, with a maximum specification. Something like "total impurities: NMT 2.0%" means the specification requires no more than 2.0% impurities — and then the result either meets that or it doesn't. This matters more than people realize, because related substances at elevated levels can change the biological behavior of a peptide in ways that are difficult to predict.

Sterility testing checks whether the product is free of microbial contamination — bacteria, fungi, mold. For an injectable compound, this is not optional. The test involves inoculating growth media with a sample from the batch and observing whether anything grows over a defined incubation period. The specification is binary: sterile or not sterile. A passing result says no growth detected. This test takes time — genuine sterility testing is not something that comes back in an hour — so a pharmacy that produces sterility results suspiciously fast may be using a method that doesn't actually meet the standard. A COA with a passing sterility result from a recognized laboratory, with the appropriate incubation period documented, is what you want to see.

Endotoxin testing is the section most people skip and the one that matters most for injectable safety. Endotoxins are lipopolysaccharides — fragments of the outer membrane of gram-negative bacteria. They are heat-stable, which means you can sterilize a solution and still have endotoxins present if they were there to begin with. Endotoxins cause fever, inflammation, and in high enough concentrations, septic shock. They are one of the most common causes of adverse reactions to injectable compounds, and they are invisible — you can't see them, smell them, or detect them without a specific test.

The test used is typically the Limulus Amebocyte Lysate assay (LAL), or a newer recombinant version. The result is given in endotoxin units per milliliter (EU/mL). The specification limit varies by route of administration and compound, but for injectable peptides the general USP standard is typically 5 EU/kg/hour — meaning the calculation depends on the dose volume and patient weight — with pharmacies usually setting a conservative internal limit expressed directly in EU/mL. A COA with a missing or blank endotoxin section on an injectable compound is a red flag. This test is not optional for anything you inject.

Residual solvents are the last major section. Peptide synthesis involves organic solvents at various stages, and the finished product should have negligible traces of those solvents remaining. The COA will list the solvents tested and give results in parts per million against ICH (International Council for Harmonisation) limits. This section is rarely the most consequential for patient safety in practice, but its presence tells you the lab did a thorough job.

Now, what "USP-grade" actually means. USP stands for United States Pharmacopeia — the organization that publishes quality standards for pharmaceutical substances and testing methods. When a pharmacy says it uses USP-grade bulk ingredients, it means the raw material was sourced to meet USP monograph specifications. That's a meaningful claim. It's not the same as FDA approval, but it indicates the raw material started at a documented quality level rather than whatever a supplier decided to ship. Look for it in the COA's notation of the reference standard used for identity and assay testing.

Three red flags that should stop you before you go further. First: no COA at all. A legitimate compounding pharmacy produces COAs for every batch and makes them available to patients. If you have to ask three times and still don't get one, that tells you something. Second: a COA that doesn't match your batch. COAs are batch-specific. The lot number on the COA should match the lot number on your vial. A pharmacy that provides a generic COA — one that doesn't reference the specific batch you received — is not actually vouching for your product. It's providing a document that looks like evidence but isn't. Third: missing sections. If a COA for an injectable compound doesn't include sterility and endotoxin, it's incomplete. A complete COA for an injectable peptide covers all six areas. Anything less is a partial document, and you should ask why the rest isn't there.

What to ask your pharmacy directly: which third-party lab performed the testing? Can you provide the lab's accreditation? Does the lot number on this COA match my vial? What is your endotoxin limit specification for this compound?

Legitimate compounders answer these questions readily. The documentation infrastructure they maintain is expensive and time-consuming. Pharmacies that have built it tend to lead with it. Pharmacies that haven't tend to become vague.

You don't need a chemistry degree to read a COA. You need to know which six sections are there, which two matter most for injectable safety, what the passing range looks like for assay, and what makes a document actually specific to your batch versus just a template someone printed. The COA exists because a compounded peptide doesn't have FDA pre-approval behind it. The testing is the quality record. Reading it is not diligence for its own sake — it's using the information that was produced specifically for you.