Fish oil vs krill oil: what's the difference?
Last updated: August 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy
Krill oil binds its omega-3s to phospholipids rather than triglycerides, which improves absorption somewhat. But krill capsules contain far less EPA and DHA per capsule and cost considerably more, so fish oil usually delivers more omega-3 per pound spent.
Key takeaways
- Krill absorbs somewhat better per milligram — but contains far fewer milligrams.
- Compare products on EPA + DHA content, never on total oil weight.
- Krill contains astaxanthin, which fish oil does not; both carry shellfish allergy risk for krill.
The absorption argument
In fish oil, EPA and DHA are attached to triglycerides or, in concentrates, ethyl esters. In krill oil they are largely bound to phospholipids, which integrate more readily into cell membranes and appear to be absorbed somewhat more efficiently. Studies suggest a modest advantage, not a dramatic one. The problem is that a typical krill capsule supplies perhaps 60–120 mg of EPA and DHA against 300–600 mg in a standard fish oil capsule and over 1,000 mg in a concentrate.
The number that actually matters
Ignore the front of the bottle. A 1,000 mg fish oil capsule is 1,000 mg of oil, of which perhaps 300 mg is EPA and DHA. Trials showing triglyceride reduction used 2–4 g of EPA + DHA daily. Reaching that on standard krill capsules would take a dozen or more per day at several times the cost. If a product does not state EPA and DHA separately on the label, that is a reason to choose a different one.
The other differences
Krill contains astaxanthin, a carotenoid antioxidant that also helps stabilise the oil against rancidity, and tends to cause less reflux and fewer fishy burps. It is also derived from crustaceans, so it is unsuitable for anyone with a shellfish allergy. Algal oil is the vegan alternative and supplies DHA, with EPA harder to obtain that way.
Key ingredients to understand
The ingredients most relevant to this question, with what the evidence actually supports:
- Omega-3 Fish Oil (EPA & DHA) — The omega-3 fatty acids EPA and DHA from fish oil have solid evidence for lowering triglycerides and are structurally important for the heart,…
- Astaxanthin — Astaxanthin is a deep-red antioxidant carotenoid from algae. Small trials suggest it mildly reduces oxidative-stress markers and may modestly…
- Krill Oil — Krill oil provides omega-3s (EPA/DHA) in phospholipid form, which may absorb well, plus natural astaxanthin. It's a pricier alternative to…
- Vitamin D — Vitamin D is essential for bones and plays a role in immunity. Deficiency is common, and supplementing clearly helps if you are low — but large…
Frequently asked questions
Which should I buy?
For cost per milligram of EPA and DHA, fish oil — ideally a concentrate. Krill is defensible if fish oil causes reflux or you specifically want astaxanthin.
How do I know it is not rancid?
Rancid fish oil smells strongly and tastes bad. Look for third-party testing for oxidation (TOTOX), and store it in the fridge.
Is there an interaction with blood thinners?
At higher doses omega-3 lengthens bleeding time. Combined with anticoagulants or antiplatelets, tell your doctor.
Related on FactoWiki
- Heart & Cardiovascular Health supplements — the full category
- All health answers
- Ingredient evidence guides
- Omega-3 Fish Oil (EPA & DHA) — ingredient guide
- Astaxanthin — ingredient guide
- How we review
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