What is TOTOX in fish oil?

Last reviewed July 2026. Figures cited to public IFOS certificates.

TOTOX (total oxidation value) is a single number for how oxidized — how rancid — a fish oil is. Fish oil is fragile: heat, light, and time turn its omega-3s into oxidation by-products that taste and smell off and degrade quality. TOTOX is the standard way that number gets reported on a third-party test.

How TOTOX is calculated

It combines two lab measurements:

• Peroxide Value (PV) — primary oxidation (early-stage).
• Anisidine Value (AV) — secondary oxidation (later-stage breakdown).

The formula is TOTOX = 2 × PV + AV. Because it captures both stages, a low peroxide value alone can't hide an oil that's already broken down further — which is why TOTOX is more honest than PV by itself.

What counts as fresh?

The Global Organization for EPA and DHA Omega-3s (GOED) sets a voluntary maximum of 26 for finished fish oil. In practice, well-made products test far lower. On our ranking we flag anything under 5 as "fresh," 5–10 as acceptable, and higher as a concern — a stricter bar than the industry ceiling, because you can afford to be picky when the data is public.

Why we put TOTOX next to price

A bottle can be cheap because the oil is old or poorly stabilized. Ranking on price alone rewards that. By showing the IFOS-tested TOTOX in the same row as cost-per-gram, cheap-but-rancid can't win on a technicality. The two IFOS-certified numbers most worth reading together are cost per gram of actual EPA+DHA and TOTOX.

How to check any product yourself

Every row in our table links the product's actual IFOS certificate PDF. The stability section lists Peroxide, Anisidine and TOTOX for the tested lot. You don't have to take our word for the number — click through and read it.

TOTOX is a freshness indicator, not a health claim. This page explains a published laboratory metric and does not diagnose, treat, or make any claim about health outcomes.