Endotoxin
Lipopolysaccharide (LPS) from the outer membrane of gram-negative bacteria, reported in endotoxin units (EU). It can remain in a sample after the bacteria are dead.
What it is
Endotoxins are lipopolysaccharides (LPS) from the outer membrane of gram-negative bacteria. They are pyrogens: substances that can trigger fever and inflammatory responses.
Killing bacteria doesn't remove endotoxin, and it is heat-stable enough that ordinary sterilisation doesn't reliably destroy it. A sample can pass a sterility test and still contain endotoxin, which is why the two are separate panels.
How it's tested and reported
Labs commonly use a Limulus amebocyte lysate (LAL) assay (gel-clot, turbidimetric or chromogenic) or a recombinant factor C (rFC) assay. Results are written in endotoxin units, usually EU/mg of peptide or EU/mL of solution.
A result written as "less than" a number, such as <0.5 EU/mg, means the amount was below what the assay can quantify, not that it was zero.
Acceptable limits depend on the intended dose and use, so there is no single universal cutoff. Some certificates print a pass/fail against the lab's limit; others print only the measured value. A value printed without a limit can't be read as a pass or a fail on its own.
How PeptideAudits reads this
- Pass or fail comes from the certificate. The EU/mg screening limit shown on report pages is a reference for context, not a verdict we apply.
- A certificate earns endotoxin points when it reports a pass, or a measured value with no pass/fail limit. Measured values are always shown as measured, never relabelled as a pass.
- A failed endotoxin result caps the report score. A certificate that doesn't mention endotoxin is "not reported", which earns no points and is not a fail.
PeptideAudits doesn't test products; values come from certificates sellers publish. See the scoring methodology.
For research use only. Not medical advice.