What is an endotoxin test?

It's a test that looks for endotoxins — fragments left behind by bacteria — in a sample. It's a separate check from a purity (HPLC) test, which only measures how much of the sample is the target molecule.

Does a high purity percentage mean there are no endotoxins?

No. Purity and endotoxin are different measurements. A sample can show high purity for identity and still carry endotoxins, because a purity test does not look for bacterial byproducts.

Which peptides most need an endotoxin test?

Compounds made biosynthetically — grown using microorganisms — are where bacterial residue is most expected. NAD+ is the common example. Chemically synthesized peptides are lower priority for this specific test.

Home › Guides › What an Endotoxin Test Shows (and When It Actually Matters)
By Toronto Health Source
Updated October 11, 2026

Canadian research peptides · independently tested

Canada’s most documented peptide source — 244 independent lab reports, a published purity floor of 93.844%, and domestic shipping.

What an Endotoxin Test Shows (and When It Actually Matters)

Growth Guys promo code, verified October 11, 2026: HEALTHYLIFE10 takes 10% off sitewide at Growth Guys (growthguys.com) on any payment method, and it is the code behind the largest total discount available there today — 30% off when the order is paid with Bitcoin, which the store discounts a further 20% automatically, so a $430.00 CAD cart paid $301.00 CAD. The measured cart, line by line.

Get 10% off with code HEALTHYLIFE10 →

We are an affiliate: if you order from Growth Guys using this code we earn a commission, at no extra cost to you. We are not Growth Guys and have no ownership of or role in the company.

Cart-tested on October 11, 2026 at Growth Guys (growthguys.com): HEALTHYLIFE10 gave 10% off sitewide, no minimum purchase and no product exclusions, reducing a $100.00 CAD cart to $90.00 CAD.

What does an endotoxin test on a peptide show? It checks for endotoxins — fragments left behind by bacteria — that a purity test (HPLC) does not detect. A peptide can read 99% pure for identity and still carry endotoxins, because the two tests measure completely different things. It matters most for peptides made biosynthetically.

Updated July 2026 · General educational information.

Why a purity number isn't the whole picture

Most COA discussion stops at "what's the purity percentage?" Here's what most people get wrong: purity (measured by HPLC) tells you how much of the sample is the target molecule versus other chemical junk. It does not look for biological contamination. Endotoxins are byproducts of bacteria, and they slip past a standard purity test entirely — so a clean HPLC number and an endotoxin problem can live in the same vial.

When does an endotoxin test actually matter?

Not equally for everything. The distinction is how the compound is manufactured. Peptides built by solid-phase chemical synthesis (like the GLP-1 class) are chemically assembled, so bacterial byproducts are less expected. But compounds made biosynthetically — grown using microorganisms because it's the cheaper route — are exactly where bacterial residue "might be expected." NAD+ is the textbook example of the biosynthetic route.

Test	What it answers	What it misses
Mass spec (identity)	Is this the right molecule?	How much is present, and contamination
HPLC (purity)	How much of the sample is the target?	Biological / bacterial contamination
Endotoxin	Are bacterial byproducts present?	Identity and chemical purity

How to use this when you read a COA

For chemically-synthesized peptides: identity + purity are the core checks; an endotoxin line is a bonus, not a dealbreaker.
For biosynthetic compounds like NAD+: an endotoxin result is the one extra test genuinely worth looking for.
Skip the scare tactics: heavy-metals testing is often marketed as a rigor signal but adds little for these compounds — it's mostly a talking point.
Remember the tests don't substitute: a great purity number never covers for a missing endotoxin check where one matters.

This builds on the basics in how to read a peptide COA and purity vs identity on a COA.

Get 10% off with code HEALTHYLIFE10 →

Cart-tested on October 11, 2026 at Growth Guys (growthguys.com): HEALTHYLIFE10 gave 10% off sitewide, no minimum purchase and no product exclusions, reducing a $100.00 CAD cart to $90.00 CAD.

Or run the free vendor-check quiz →

Why this vendor, specifically

Because the claims are the kind you can verify before spending anything. Growth Guys has published 244 Janoshik reports across 133 distinct products — 99.03% average purity, floor 93.844%, ceiling 99.99% — and each report lives on the testing lab's site, not behind a vendor-hosted PDF. Shipping is domestic within Canada in CAD, and the vendor has fielded questions in public forum threads since November 2021. The full distribution is here.