Compare omega-3 and fish oil supplements on the amount of EPA and DHA in each daily dose, not the total amount of oil, and on the cost per day. Fish oil, cod liver oil, krill oil, plant oils and vegan algae-based products all sit here, and they are not interchangeable, so we explain the differences before you buy.
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What is omega-3?
Omega-3s are a family of fats. The two found in oily fish and fish oil are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), and the plant version is ALA (alpha-linolenic acid), found in foods such as linseed, walnuts and rapeseed oil.
Your body can make some EPA and DHA from ALA, but the British Dietetic Association says this happens slowly and only small amounts are formed. That's why flaxseed and pumpkin seed oils, which we also stock, are not a like-for-like swap for fish or algae oil.
Do you need an omega-3 supplement?
Most people don't need one if they eat fish. The NHS says a healthy, balanced diet should include at least 2 portions of fish a week, including 1 of oily fish, such as salmon, sardines, mackerel or trout.
The British Dietetic Association goes further: it says omega-3 supplements are not recommended in the UK general population, because the evidence of benefit is inconclusive. If you don't eat fish and choose a supplement, it suggests looking for about 450mg of EPA and DHA per daily adult dose.
"Where evidence is limited or inconclusive, we should say so openly," says Andy Arshad, who runs SupplementHQ.
What can omega-3 supplements claim?
Only a few claims are authorised, and each comes with conditions. "EPA and DHA contribute to the normal function of the heart" can be used only for a food that is at least a source of EPA and DHA, and the reader must be told the effect comes with a daily intake of 250mg of EPA and DHA.
"DHA contributes to maintenance of normal brain function" and "DHA contributes to the maintenance of normal vision" need 250mg of DHA a day. Check the label: some products, especially gummies, may contain less than that per daily dose. We don't use any other heart, brain or joint wording.
Fish oil or cod liver oil: what's the difference?
Fish oil comes from the flesh of oily fish, while cod liver oil comes from the liver and is also high in vitamin A. The NHS says fish liver oil is high in vitamin A, and having more than an average of 1.5mg (1,500 micrograms) a day of vitamin A over many years may affect your bones.
So if you take cod liver oil, count its vitamin A along with any multivitamin. The BDA advises choosing omega-3 supplements over fish liver oil. Some products here also add vitamins A, D, E or K (such as "ADEK" or "D3 + K2" formulas), so check those amounts too.
| Type | Main omega-3 | Worth knowing |
|---|---|---|
| Fish oil / salmon oil | EPA and DHA | Compare EPA + DHA per dose, not oil |
| Cod liver oil | EPA and DHA | Also contains vitamin A; avoid in pregnancy unless your GP advises otherwise |
| Krill oil | EPA and DHA | From a crustacean; check allergens |
| Algae oil (vegan) | Mainly DHA, sometimes EPA | The fish-free option for EPA/DHA |
| Flaxseed / pumpkin seed oil | ALA | Converted to EPA/DHA only in small amounts |
Is omega-3 safe in pregnancy?
Fish oil without vitamin A is a different product from fish liver oil. The NHS says unless your GP advises otherwise, avoid taking fish liver oil supplements when you're pregnant or trying for a baby, because of the vitamin A they contain.
The NHS also says girls and women who are pregnant, breastfeeding or planning a pregnancy should have no more than 2 portions of oily fish a week. If you're pregnant, speak to your midwife, GP or pharmacist before taking any omega-3 supplement. We stock prenatal DHA products, including a vegan one; see pregnancy and fertility supplements.
Is there a vegan omega-3?
Yes. The BDA says some supplements contain only algae so are suitable for vegetarians and vegans. Fish get their omega-3 from algae, so algae oil provides DHA (and in some products EPA) directly.
Fish, crustaceans and molluscs are among the 14 allergens that must be emphasised on food labels, so check the ingredients list if you have an allergy. Krill is a crustacean.
How much omega-3 is too much?
EFSA, the European food safety authority, says supplemental intakes of EPA and DHA combined of up to about 5g a day do not raise safety concerns for adults. Most daily doses are far below that.
High doses may affect bleeding when taken with blood-thinning medicines: the US National Institutes of Health says high doses of omega-3s may cause bleeding problems when taken with warfarin or other anticoagulants. Speak to your GP or pharmacist first if you take medication or have a medical condition.
How to compare omega-3 on value
Compare the cost per 1,000mg of EPA + DHA, not per capsule. A "1,000mg fish oil" capsule usually contains much less than 1,000mg of EPA and DHA.
How to compare value (example figures, not real products): a £10 tub of 90 fish oil capsules with 300mg of EPA + DHA each provides 27,000mg in total, so about 37p per 1,000mg. A £15 tub of 60 capsules with 600mg each provides 36,000mg, about 42p per 1,000mg. A £14 pack of 60 gummies with 100mg each provides 6,000mg, about £2.33 per 1,000mg.
"We think customers should compare the actual amount of active ingredients they're getting, rather than just the format or marketing," says Andy. Go back to all vitamins and supplements, or read our guide to reading a supplement label.
We sell the products on this page. That's our commercial interest, and it's why we show the evidence alongside them. This page is general information for adults, not personalised medical advice. Food supplements should not replace a varied, balanced diet.
Written by Andy Arshad, SupplementHQ. Last reviewed 11 October 2026.