What is TOTOX in fish oil?
Last reviewed October 2026 — peroxide, anisidine and TOTOX re-read from every IFOS certificate on 4 October 2026, and the GOED limits from the GOED Voluntary Monograph (version 9.1) the same day.
TOTOX is 2 × peroxide value + anisidine value, and lower is fresher. IFOS's limit, printed on every certificate, is 19.5; the GOED Voluntary Monograph (version 9.1) allows up to 26. The 10 IFOS-certified fish oils on this site measure 3.49 to 17.74: lowest Wiley's Finest Peak EPA (lot 124068, which expired 02/2021), lowest current lot Viva Naturals Triple Strength Omega-3 at 6.44, highest Carlson Elite Omega-3 Gems. Each value read from the product's own IFOS certificate on 2026-10-04.
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 its voluntary monograph. 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.
TOTOX, peroxide and anisidine by product
Each row is the stability section of the product's public IFOS certificate, read 2026-10-04, sorted freshest first. IFOS limits: peroxide ≤ 5 meq/kg, anisidine ≤ 20, TOTOX ≤ 19.5. GOED limits: 5, 20 and 26; GOED says its anisidine and TOTOX limits do not apply to flavoured oils (here Carlson The Very Finest Fish Oil and Carlson Elite Omega-3 Gems).
| Product | Peroxide (meq/kg) | Anisidine | TOTOX | IFOS certificate |
|---|---|---|---|---|
| Wiley's Finest Peak EPA (figures from lot 124068, which expired 02/2021; no current lot is published) | 1.37 | 0.75 | 3.49 | lot 124068 |
| Viva Naturals Triple Strength Omega-3 | 1.18 | 4.08 | 6.44 | lot SG26050703 |
| OmegaVia DHA 600 | 2.82 | 1.09 | 6.73 | lot OV250191 |
| Carlson The Very Finest Fish Oil | 0.89 | 7.5 | 9.28 | lot 0011224 |
| Sports Research Triple Strength Omega-3 | 1.61 | 6.36 | 9.58 | lot UC260228 |
| Life Extension Super Omega-3 | 2.75 | 5.91 | 11.41 | lot C2600194 |
| OmegaVia EPA 500 | 4.30 | 4.25 | 12.85 | lot OV250446 |
| OmegaVia Ultra Concentrated Omega-3 | 0.18 | 14.48 | 14.84 | lot OV250490 |
| Carlson Super Omega-3 Gems | 3.45 | 10.31 | 17.21 | lot SB017012 |
| Carlson Elite Omega-3 Gems | 3.87 | 10 | 17.74 | lot SB017377 |
California Gold Nutrition's two iTested reports (iHerb's in-house programme) print no TOTOX, so they are not in this table. Contaminant and heavy-metal results from the same certificates: fish oil heavy metals, by product.
What a TOTOX or peroxide value means
What is a good TOTOX value for fish oil?
Lower is fresher. The IFOS limit is 19.5, and the GOED Voluntary Monograph (version 9.1) sets a maximum of 26. The 10 IFOS-certified fish oils on Fish Oil Score measure 3.49 to 17.74 (certificates read 2026-10-04); this site calls under 5 fresh and 5 to 10 acceptable.
What does the peroxide value of fish oil mean?
Peroxide value (PV) measures early-stage oxidation, in milliequivalents per kilogram. IFOS and GOED both set a maximum of 5 meq/kg. The IFOS certificates on this site print 0.18 meq/kg (OmegaVia Ultra Concentrated Omega-3) to 4.30 meq/kg (OmegaVia EPA 500), read 2026-10-04.
What does the anisidine value of fish oil mean?
Anisidine value (p-AV) measures later-stage oxidation by-products. IFOS and GOED both set a maximum of 20. The IFOS certificates on this site print 0.75 (Wiley's Finest Peak EPA) to 14.48 (OmegaVia Ultra Concentrated Omega-3), read 2026-10-04. GOED notes the anisidine method is not applicable to flavoured oils.
Which fish oil has the lowest TOTOX?
Of the fish oils we track, Wiley's Finest Peak EPA at 3.49, but that is lot 124068, which expired 02/2021. The lowest current lot is Viva Naturals Triple Strength Omega-3, lot SG26050703, at TOTOX 6.44 (IFOS certificate read 2026-10-04).
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 that product's certificate page here, and each of those pages links the IFOS certificate PDF itself — so it is two clicks to the source, not one. The stability section of the PDF lists Peroxide, Anisidine and TOTOX for the tested lot. You don't have to take our word for the number: open the certificate and read it. Every certificate link on this site was re-checked on 4 September 2026 and all of them resolve.
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.