How to Read a Peptide Certificate of Analysis (and Spot a Fake)

I want to give you the single highest-leverage skill in this whole space, and it isn't a peptide. It's a piece of paper.

A Certificate of Analysis (COA) is the one document that tells you whether the vial in your hand actually contains what the label says. Without a real one from a credible lab, you're just trusting the vendor's word. With one, you can verify purity, identity, batch, sterility, and contamination before anything goes into your body.

Here's why this isn't optional: Janoshik Analytical, one of the field's leading third-party testing labs, reported that in 2024, 43% of the peptides submitted to them failed to meet their label's purity claims. Lower-tier vendors tested at 71–91% actual purity on products marketed as 99%+. That's not a handful of bad actors — that's close to half the gray-market peptide supply failing a basic purity check. Learning to read a COA is how you stop rolling those dice.

Get the terminology right first

You'll see two terms used interchangeably, and only one of them is correct.

• Certificate of Analysis (COA) — the real term. A third-party lab tests the product (HPLC for purity, mass spectrometry for identity, LAL testing for endotoxins) and reports what they found.
• Certificate of Authenticity — the wrong term, but you'll see it on plenty of vendor sites. It describes provenance, not chemistry — it's the language you'd use for a signed autograph, not a lab result. If a vendor calls their document a "Certificate of Authenticity," that's a small tell they're not fluent in the actual testing workflow.

From here on, COA means Certificate of Analysis.

What a real COA actually shows you

A credible COA from a credible lab includes, at minimum:

1. The testing lab's identity — name, address, contact info you can actually reach.
2. A unique report number you can verify directly with the lab.
3. Compound identity, confirmed by mass spectrometry, with a molecular weight that matches the published number for that compound (BPC-157 = 1419.55 Da; Retatrutide = 4731.27 Da; full-length TB-500 = 4921 Da).
4. Purity percentage, measured by HPLC. My own bar: anything under 99% is a yellow flag, under 98% is a red flag.
5. Actual content amount — the milligrams of peptide really in the vial, separate from the label number. A "10 mg" vial might test at 8.5 mg, 10.2 mg, or 14.7 mg, and each of those tells you something different (more on this below).
6. Sterility testing — culture-based confirmation there's no microbial contamination.
7. Endotoxin (LAL) testing — confirms bacterial cell-wall debris is below a safe threshold. Genuinely important, not overcaution: endotoxin in an injectable can cause real pyrogenic reactions (fever, chills, hypotension), and the FDA regulates endotoxin limits in pharmaceuticals for a reason.
8. Batch identifier, matching the batch label on your actual vial.
9. Ideally, a photo of the tested bottle — including cap color and seal color. This is the single most useful verification trick in the entire process.

The cap-and-seal trick — your best verification step

Manufacturers typically use different cap and seal colors for different production batches, as an internal tracking convention, and generally don't repeat a color combination within a year. If the COA includes a photo of the tested bottle, that photo shows you the exact cap and seal color of the batch that was actually analyzed.

When your order arrives, compare its cap color and seal color to the photo on the COA.

• Match — the COA is plausibly for your batch. Still verify the report number with the lab, but you've cleared the first check.
• No match — you may have received a different batch than the one that was tested, which means the published COA tells you nothing about what's actually in your vial. Email the vendor and ask for the COA matching your batch number or your cap/seal color. If they can't produce one, that's a real red flag.

Some labs charge extra to include the bottle photo, so not every COA has one. If yours doesn't, lean harder on matching the batch number printed on the vial to the one on the COA, and don't hesitate to ask the vendor for a fresh one.

Underfill vs. overfill — why this changes your dosing math

A "10 mg" vial doesn't always contain exactly 10 mg. The COA's actual-content number tells you the truth, and it matters more than people realize:

• Underfill (actual < label): safer direction. If you dose off the label number, you'll under-dose, not over-dose.
• Close enough (within ~5% of label): functionally the same as label dosing.
• Overfill (actual > label): this is where it gets risky, especially for anything you titrate carefully. A "0.5 mg starting dose" calculated off the label is actually higher than you think. For a compound like retatrutide, that can be the difference between tolerable nausea and an ER visit — one documented test found a 10 mg vial from a major vendor averaged 12.1 mg actual, a 20% overfill.

For compounds where you're not titrating carefully — GHK-Cu, BPC-157, TB-500 — overfill mostly just means extra product for your money. For anything with a real dose-response side-effect curve, like GLP-1 receptor agonists, read the actual-content number and adjust your reconstitution math accordingly. Don't just trust the label.

Testing labs worth trusting

Janoshik Analytical (Europe) is widely regarded as the gold standard — HPLC purity, mass spec identity, sterility, and LAL testing, with a unique verifiable report number on every result. Freedom Diagnostics and Peptide Test (both US-based) are other well-known independent options. Beyond those, look for any lab that publishes its methodology, charges per-test rather than working as a captive vendor partner, and issues verifiable report numbers.

One historical fake worth knowing: "Freedom Pharmacy" (distinct from Freedom Diagnostics) was a fake lab name used to produce Photoshopped COAs, reportedly out of a Southern California reseller — a real example of exactly the scam pattern below.

How to actually verify a Janoshik COA (takes about 90 seconds)

The most common fake-COA scam works like this: someone takes a real Janoshik report for a different product, opens it in Photoshop, and swaps only the company name at the top. All the purity numbers, lot codes, and batch info stay untouched, because the goal is to look like a genuine, already-tested result. This is exactly why the verification step matters — the numbers on the page can be completely real and still not be about your product.

1. Find the Task Number (top) and Unique Key (bottom, a string of letters and numbers) on the COA.
2. Go to janoshik.com, use their public verification tool, and enter both values.
3. You'll get one of two answers: the test is in their database (you can open the real report), or it isn't — in which case the COA is fake, and you shouldn't buy.
4. If it's real, put the real report side by side with the COA the vendor showed you. Compare the company name, product name, batch number, and purity numbers. A mismatched company name means you've caught a Photoshopped-header scam — don't buy, and consider flagging the listing wherever you found it.

Finnrick — the free-testing alternative

Alongside Janoshik, Finnrick Analytics (Texas-based) runs a donation-funded, free community testing project. As of mid-2026 they've rated 263 vendors across roughly 8,700 samples spanning 15 peptides, with a browsable public vendor list at finnrick.com/vendors. They score each sample 0–10 (purity, quantity accuracy, and batch-info quality), not the A–F grading you'll sometimes see it mistranslated into online — the lab's own scale is 0–10.

The strongest move is using both: check whether your vendor shows up in Finnrick's list, and verify any Janoshik COA they publish using the steps above. Combined with your own cap-and-seal check against the COA photo, that's about as much verification as a customer can do without running their own lab.

Your practical checklist

1. Confirm the batch number on your vial matches the COA's batch number.
2. Check the cap and seal color against the COA's bottle photo, if it has one.
3. Confirm the testing lab is a real, findable, verifiable one — not a name that only exists on that one PDF.
4. Verify the report number directly with the lab if you can.
5. Read the actual-content number, not just the label number, and adjust your dosing math if they differ.
6. Check the purity percentage — under 99% is a yellow flag, under 98% is a red flag.
7. Confirm sterility and endotoxin testing are present.
8. If anything doesn't add up, don't inject it. A wasted purchase is a much smaller loss than an unverified injection.

Buying from a vendor that already publishes real, verifiable third-party COAs as standard practice (see where to buy) does most of this work for you before you even open the box. But the whole point of this article is that you don't have to take anyone's word for it — you can check.

For the bigger supply-chain picture — where these peptides are actually manufactured and what "Made in USA" really means on a label — see where peptides are actually made. For how the mainstream medical establishment views this same verification question, see the conventional-medicine perspective.

Sources: Janoshik Analytical 2024 purity-testing data (janoshik.com); Finnrick Analytics public vendor database (finnrick.com/vendors); Van Wagoner et al., "Selective Androgen Receptor Modulators (SARMs) in Sports Supplements," JAMA Internal Medicine 2017 (PMID 29183075) — comparable supply-chain contamination pattern in a different research-chemical category.

Educational information only, not medical advice. Peptides discussed here are sold for research use only and are not FDA-approved for human use.