What is the TOTOX value of fish oil?

TOTOX is a calculated index of oxidation in the oil examined. It combines two laboratory values: peroxide value and p-anisidine value. The result concerns the tested sample; it does not establish how much DHA+EPA it contains or which contaminants were measured.^[5]

A number without a report, batch reference or test date therefore lacks important context. To interpret it, you need to know where it came from.

How is TOTOX calculated?

TOTOX stands for total oxidation. The formula is:

TOTOX = 2 × peroxide value (PV) + p-anisidine value (pAV).^[5]

The laboratory determines PV and pAV. TOTOX follows as a calculation. Use values that belong to the same tested sample and measurement time. Two figures from different batches cannot be combined into one result.

A TOTOX value of 8 does not mean that 8% of the oil is oxidised. Nor is it a score of 8 out of 10 or 100.

What does peroxide value measure?

Peroxide value, abbreviated PV, provides information about primary oxidation products in the oil. The usual unit is milliequivalents of active oxygen per kilogram of oil: meq/kg.^[2]

Check the unit in the report. A value reported in mmol/kg cannot be used as the same numerical value in meq/kg without conversion.

PV is one part of the oxidation assessment. Copying a PV alone and calling it “TOTOX” is incorrect: p-anisidine value is still missing.

What does p-anisidine value measure?

P-anisidine value, abbreviated pAV, measures certain aldehydes. These include substances that can form during further oxidation. It is a different determination from PV.^[2][3]

Reports may also use p-AV or AnV. Check the full name: AV can mean acid value in another report. Acid value cannot replace pAV in the TOTOX formula.^[2]

PAV is not a percentage of the oil or an amount of DHA+EPA either.

Which TOTOX limit is commonly cited?

The voluntary GOED Monograph, version 8.1 dated 6 January 2022, specifies these maxima for the oils and determinations to which they apply:^[1]

These figures refer to that particular monograph. “26” should not be read as a general product approval or a standalone verdict on every omega-3 format.

Check which specification and version the report uses, and whether they apply to the oil and method examined. The monograph has a defined scope and refers flavoured oils to additional technical guidance.^[1]

Why check PV and pAV separately too?

A TOTOX below 26 does not establish that both individual values also meet the stated maxima.

The calculated TOTOX is below 26. However, PV of 6.0 exceeds the separate GOED maximum of 5 meq/kg. The combined figure therefore does not replace the individual requirements.

A lower TOTOX number is also comparable only when the measurements and context allow it. It is not a basis for declaring another product a winner without further information.

Can flavouring affect the measurement?

Some flavourings can interfere with p-anisidine determination. A measured pAV can then also respond to substances from the flavouring. That affects the usefulness of a directly calculated TOTOX.^[4]

This does not mean every flavoured oil has the same issue. It means the method and any corrections need supporting evidence. A 2020 study also showed that flavourings’ contribution can change during storage, so a fixed correction is not necessarily sufficient.^[4]

GOED’s additional guidance discusses these limitations and procedures for flavoured oils.^[2] Do not draw a conclusion from the number on a product page alone. Check how it was determined.

Can fish oil, algae oil and krill oil be compared this way?

Do not assume every oil can be assessed using the same method. Supplement research shows that formulation can affect whether the determinations can be performed.^[5]

A comparison requires evidence that the determinations are suitable for the oil and any additions. Without that check, a lower number for another oil type does not establish a difference in oxidation.

A missing or unusable TOTOX result does not automatically prevent other comparisons. The source, declared DHA and EPA amounts and price can still be examined separately.

What should accompany a published result?

Read a TOTOX statement with its underlying report. Check:

• Product and batch. Does the identification match your pack?
• Tested material. Does the report concern the ingredient oil or the finished supplement?
• Dates. Distinguish the test date from the report date and best-before date.
• Underlying figures. Are PV, its unit and pAV stated, or only the calculated total?
• Method. Is it suitable for this oil, including any flavourings?
• Comparison. Which specification, version and limits does the report use?
• Issuer and sample. Which laboratory examined the sample, and who supplied or selected it?

Also distinguish a result from a requirement. “TOTOX maximum 26” may be a product specification. It is not automatically a measured TOTOX result of 26.

A measurement of an ingredient sample is not a measurement of the finished capsules. Nor can a result for one batch be assigned to every batch of the product without further supporting evidence.

What can’t TOTOX establish?

TOTOX does not replace a DHA+EPA measurement or testing for substances such as metals, dioxins or PCBs. Those are separate questions.

The result does not automatically establish what would be measured later in another pack either. That needs additional information; a test date and a best-before date are different facts.

If no public report can be found, the measured value remains unknown to you. That does not establish that the oil was not tested. Do not enter a missing result as zero or read it as an exceedance.

Reading TOTOX information on SUPPFAX

SUPPFAX compares label information and available Netherlands shop prices. When examining published test information attached to a product, read it with its source, date and the material to which it applies.

Price per gram of DHA+EPA and an oxidation result answer different questions. Together, they help explain the available information; neither provides a complete product verdict on its own.

Sources

Consulted on 31 October 2026.

1. GOED Voluntary Monograph, version 8.1, 6 January 2022. For the formula, stated maxima and scope. This is a voluntary industry specification. ↩ ↩
2. GOED Technical Guidance Documents, PDF linked when checked on 31 October 2026. For oxidation determinations, PV units, acid value and guidance for flavoured oils. Document sections have their own version dates. ↩ ↩ ↩ ↩
3. ISO 6885:2016 — determination of anisidine value. The public abstract describes the aldehydes measured; the full standard has not been reproduced. ↩
4. Study of flavourings and p-anisidine determination, 2020. For measurement interference and corrections during storage. ↩ ↩
5. Study of oxidation determinations in omega-3 supplements, 2015. For the calculation and limitations of analytical applicability. Its Canadian market findings are not presented as findings about Netherlands products. ↩ ↩ ↩