How does cod liver oil differ from fish oil?
5 min read
Cod liver oil is a type of fish oil obtained from the livers of cod and related fish.[1] Alongside DHA and EPA, it can supply vitamin A and vitamin D.[2]
The distinction therefore goes beyond the oil source. Compare the individual DHA and EPA amounts and any declared vitamins too. The product name does not establish a fixed composition or amount.
Is cod liver oil different from fish oil?
“Fish oil” is the broader term. “Cod liver oil” also identifies the part of the fish used. Its definition specifies the livers of cod and other fish in the cod family.[1][3]
If a pack says only “fish oil”, that name alone does not establish which fish species or tissue was used. Check the ingredients list and any additional source information.
A separate shop category does not make cod liver oil a different type of fatty acid. Both cod liver oil and other fish oil products can contain DHA and EPA.[2]
How do their compositions differ?
Vitamin A and vitamin D are relevant details alongside the omega-3 fatty acids in cod liver oil.[1][2][3] Check the specific product’s information for the actual amounts.
| Detail | Cod liver oil | Other fish oil products |
|---|---|---|
| Oil source | Fish liver; check the declared species | Check the declared oil source and species |
| DHA and EPA | Establish amounts for the product | Establish amounts for the product |
| Vitamin A and vitamin D | Check individual declarations | Check whether they are declared or added |
| Other ingredients | Read the full ingredients list | Read the full ingredients list |
A fish oil product can also contain added vitamins. Vitamin D alone does not make the oil cod liver oil: the oil source and added ingredients are separate details.
Conversely, a missing vitamin declaration does not automatically mean the product contains 0 micrograms. Record what the source declares and what remains unknown.
How do you compare label amounts?
First put the figures on the same basis. An amount per capsule is not directly comparable with one per two capsules or per 5 ml.
This fictional example refers to one capsule for each product. All figures are invented to explain the composition differences. They are neither test results nor intake advice.
| Label declaration per capsule | Cod liver oil example | Other fish oil example |
|---|---|---|
| Oil | 1,000 mg | 1,000 mg |
| DHA | 100 mg | 120 mg |
| EPA | 80 mg | 180 mg |
| DHA+EPA, calculated from the label | 180 mg | 300 mg |
| Vitamin A | 250 µg RE | Not listed |
| Vitamin D | 5 µg | Not listed |
Both examples declare the same amount of oil. Their DHA+EPA totals differ: 100 + 80 = 180 mg versus 120 + 180 = 300 mg.
The vitamin figures describe another part of the composition. Do not add vitamin A and vitamin D to DHA+EPA. “Not listed” in the table remains unknown rather than zero.
These figures describe only the fictional labels. They do not establish a fixed ratio or concentration for either oil category.
What do the vitamin units mean?
DHA and EPA amounts are usually expressed in milligrams, abbreviated mg. Vitamin amounts can be expressed in micrograms: µg or mcg. One milligram is 1,000 micrograms.
The European food supplements directive lists µg RE for vitamin A and µg for vitamin D.[4] RE means retinol equivalents. That qualifier belongs to the vitamin A declaration and should remain when label information is recorded.
Keep both the number and the full unit. Do not treat different units or a percentage of a reference intake as the same figure. This article does not convert vitamin amounts into international units.
Can you use price per gram of DHA+EPA?
Yes, if the DHA+EPA total and pack contents are known. First calculate the grams of DHA+EPA declared for the whole pack, then divide the pack price by that number of grams.
The result compares the cost of DHA+EPA. It assigns no separate monetary value to vitamin A, vitamin D or other components.
Two products can therefore have the same DHA+EPA total while differing in composition. Keep the vitamin details visible and compare products within an appropriate composition group. Price per gram does not establish that cod liver oil and another fish oil product are interchangeable for the same use.
For the full calculation sequence, see How to read an omega-3 supplement label.
What does the oil source establish about test results?
The words “cod liver oil” and “fish oil” do not establish which measurements were performed on a product or batch.
Measured DHA, EPA or vitamin amounts require a relevant report. Oxidation and contaminants require their own determinations. Check the source, date, material examined and batch connection where applicable.
A label declaration is not a public batch report. Not finding a public report does not establish that a product was not tested either.
Read more in How to read a laboratory report for omega-3.
Which details should you compare?
Check the oil source, DHA and EPA, vitamin declarations, serving basis, pack contents and full ingredients list. Record missing information without turning it into a quality judgement.
On SUPPFAX, DHA+EPA amounts declared on labels form the basis of the price comparison. The rest of the composition remains relevant alongside that figure. A price calculation does not establish which vitamins or supplement someone needs.
Sources
Consulted on 31 October 2026.
- National Library of Medicine — MeSH: Cod Liver Oil. For the definition of cod liver oil and its classification as a fish oil. ↩ ↩ ↩
- NIH Office of Dietary Supplements — Omega-3 Fatty Acids, Health Professional Fact Sheet. For omega-3 supplements and vitamin A and vitamin D in cod liver oil. Stated source update: 22 August 2025. ↩ ↩ ↩
- United States Pharmacopeia — Cod Liver Oil, public definition. For the oil source and vitamin components. The public page cites the 2020 edition; the full monograph requires access. ↩ ↩
- Directive 2002/46/EC, consolidated text of 26 November 2025, Annex I. For the vitamin units cited. RE means retinol equivalents. ↩
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