Health & Wellness · Peptides

How to Read a Peptide COA Before You Buy

By Janet Von Schmeling
Creative Director, Planet Janet TV · August 2026 · 6 min read

Quick disclosure: I'm a paid affiliate for Feel Peptides, so I earn a commission if you buy through my link or code. I'm not a doctor or a chemist, and this is not medical advice. It's just the checklist I use so I don't buy blind.

If there's one habit I'd want anyone looking into peptides to steal from me, it's this: never buy without seeing the Certificate of Analysis. A COA is the lab report that says what's actually in the vial. When I first started reading these they looked like gibberish, so here's the plain version.

What a COA is: a third-party lab document showing the identity and purity of a specific batch. "Third-party" matters. A company grading its own homework is not the same as an independent lab doing it.

The four things I actually look at

1. Purity percentage (aim high)

This is the headline number. It tells you what portion of the sample is the actual peptide versus leftover junk from manufacturing. A trustworthy report usually shows purity in the high 90s. I want to see 98% or higher. Anything vague, missing, or surprisingly low is a walk-away for me.

2. HPLC (how they measured purity)

HPLC stands for high-performance liquid chromatography. You don't need the science, just know it's the standard method for separating out what's in the sample and measuring purity. A real COA shows the HPLC chart, usually one tall clean peak. Lots of extra little peaks means more impurities.

3. Mass spec (did they confirm it's the right thing)

Mass spectrometry confirms the molecule's identity, that it weighs what the correct peptide should weigh. Purity tells you how clean it is; mass spec tells you it's actually the peptide on the label and not something else. I want both.

4. The details that prove it's real

A batch or lot number that matches the vial you're buying, not a generic sample.
The testing lab's name and a recent date. A COA from years ago on a fresh batch is a mismatch.
The product name and sequence spelled out, matching what you ordered.

My rule of thumb: if a company won't show a batch-specific, third-party COA before you pay, that tells you everything. The good ones make it easy to find. That transparency is a big part of why I use the company I use.

Red flags that end it for me

No COA at all, or "email us and we'll send one" that never comes.
A COA with the lab name blacked out or missing.
Purity numbers that don't match the HPLC chart, or no chart shown.
The same generic COA reused for every product (a real one is batch-specific).
Prices that are dramatically cheaper than everyone else. That's usually a sourcing or purity story you don't want.

Why this matters more than the peptide itself

Here's the thing I keep coming back to: with research-use-only products, the biggest risk isn't the peptide, it's the source. Two vials with the same name can be worlds apart in what's actually inside. The COA is how you tell them apart. It's also why "is it legal" (I wrote about that here) is only step one. Clean sourcing is step two, and honestly the one I care about most.

See the COAs on the products I use →

Paid link. Feel Peptides' products are labeled for laboratory research only and are not FDA approved. This is not medical advice. Talk to your own doctor before starting anything. Code JANET10 saves 10%.

Frequently asked questions

What is a COA for peptides?

A Certificate of Analysis is a lab report for a specific batch showing the peptide's identity and purity, usually measured by HPLC and confirmed by mass spectrometry. A trustworthy one is done by an independent third-party lab.

What purity should I look for?

Reputable peptide COAs typically show purity in the high 90s. Many people look for 98% or higher. Missing, vague, or low numbers are a reason to walk away.

What do HPLC and mass spec mean?

HPLC is the method used to measure purity, shown as a chart with peaks. Mass spectrometry confirms the molecule is actually the peptide it claims to be by verifying its weight. Good reports include both.

What if a company won't provide a COA?

That's a red flag. Transparent companies make batch-specific, third-party COAs easy to find before you buy.

Heads up: I'm a paid affiliate for Feel Peptides and I earn a commission if you buy through my link or code, at no extra cost to you. I'm not a doctor, chemist, or scientist and nothing here is medical advice. Peptide products sold this way are typically labeled for laboratory research only and are not FDA approved, meaning they were not made or tested for human use. Reading a COA is a way to evaluate sourcing quality, not a safety guarantee. Always talk to your own doctor before making any decision, especially if you're pregnant, nursing, on medication, or managing a health condition.

Janet Von Schmeling

Creative Director behind Planet Janet TV. I have no medical or scientific training. I share the real research and finds I actually use, and I'm honest about what I don't know. Say hi on Instagram.

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Sources: General analytical chemistry references on HPLC and mass spectrometry for peptide purity · Feel Peptides published Certificates of Analysis, retrieved August 2026. This is education, not medical advice.