Fish Oil vs Krill Oil
Fish oil and krill oil compared: how the omega-3 is packaged, trials with conflicting absorption results, cholesterol evidence, dose-matching problems, and how cod liver oil differs.
Content last updated . This page has not been medically reviewed.
The question
Is krill oil better than fish oil? Short answer: trials conflict on absorption, a pooled analysis found no difference in lipid effects, and no head-to-head trial of heart, joint or brain outcomes was found. There is no universal winner. This page is information only.What each option is
Fish oil carries EPA and DHA mainly bound in triglycerides. [1] NCCIH describes krill oil as containing omega-3s in the form of phospholipids. [2] Cod liver oil is a fish liver oil that also contains vitamins A and D. [2] Profiles: Fish oil, Krill oil, Cod liver oil.Documented differences and head-to-head evidence
| Question | What the source found | Strength of evidence |
|---|---|---|
| Is krill oil absorbed better? | In a single-dose crossover trial in 15 people, EPA and DHA in krill oil had higher 72-hour bioavailability than in krill meal or fish oil. [1] | Short-term, small |
| Does it raise the omega-3 index more? | In 24 healthy volunteers, krill oil raised the omega-3 index more than fish oil after 4 weeks, each providing 600 mg of omega-3. [3] | Crossover, small |
| Equal EPA plus DHA | In 66 adults taking 1.3 g a day of EPA plus DHA for 4 weeks, total plasma EPA plus DHA did not differ significantly between groups (p = 0.052). [4] | Randomized, matched amounts; study amount, not advice |
| 12 weeks, omega-3 index | In 62 participants, the rise in the omega-3 index was comparable between fish oil, krill oil and Calanus oil. [5] | Randomized, parallel |
| Cholesterol and triglycerides | A network meta-analysis of 64 randomized trials reported that the lipid-modifying effects of krill oil and fish oil do not differ. [6] A separate analysis of 14 krill trials (1,458 participants) reported benefits for total cholesterol, most clearly in trials under 8 weeks. [7] | Moderate for blood lipids; not clinical outcomes |
| Heart attacks, strokes, joint or brain outcomes | Proper evidence not found. We searched PubMed for head-to-head trials of fish oil versus krill oil on these outcomes and found none in the sources we read. | Insufficient evidence |
Why results conflict
Krill oil has a lower concentration of EPA and DHA, so dose differences complicate comparisons. [8] A 2014 critique argued that the dosage differential was too small to explain the claimed differences in blood levels, and concluded there was no evidence of greater bioavailability at that time. [8] Later trials gave mixed results, as above. Higher blood levels are a marker, not a benefit.No universal winner
What can be compared is the EPA plus DHA each serving actually provides: How to read a fish oil label.Frequently asked questions
Is krill oil better absorbed than fish oil?
Results conflict. One trial found higher 72-hour bioavailability for krill oil, while a matched-amount four-week trial found no significant difference. [1][4]
Does krill oil lower cholesterol more than fish oil?
A network meta-analysis found no difference in lipid effects. [6]
Is cod liver oil the same as fish oil?
No. Cod liver oil is a fish liver oil that also contains vitamins A and D, which can be harmful in excessive amounts. [2]
Does krill oil need a lower amount than fish oil?
Proper evidence not found. Compare the EPA and DHA per serving, and ask a clinician or pharmacist about your own situation.
Is krill oil safe for everyone?
No. Ask about allergy, medicines, pregnancy and surgery first. [9]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read the evidence labels
Labels used on this page: evidence in adequately nourished people, mixed, insufficient evidence.
Safety and who should ask a clinician
- Side effects of omega-3 supplements are usually mild, such as taste, bad breath, heartburn, nausea or diarrhea. [2]
- Fish liver oil supplements are high in vitamin A. NHS advises avoiding them in pregnancy and says not to have more than 1.5 mg of vitamin A a day from food and supplements combined (UK advice). [9]
- NHS notes allergies to fish or shellfish are quite common and can cause severe reactions. [9] Whether krill oil suits a person with a fish or shellfish allergy was not addressed in the sources we read, so ask an allergist.
- Blood thinners, other medicines, pregnancy, children, kidney or liver conditions and upcoming surgery: ask a clinician or pharmacist. See Omega-3 safety and interactions and How interactions work.
References
- Köhler A, et al. Lipids Health Dis 2015. Bioavailability of fatty acids from krill oil, krill meal and fish oil in healthy subjects: a randomized, single-dose, cross-over trial. Read 2026-10-22.
- NCCIH. Omega-3 Supplements: What You Need To Know. US, last updated November 2024. Read 2026-10-22.
- Ramprasath VR, et al. Lipids Health Dis 2013. Enhanced increase of omega-3 index in healthy individuals with response to 4-week n-3 fatty acid supplementation from krill oil versus fish oil. Read 2026-10-22.
- Yurko-Mauro K, et al. Lipids Health Dis 2015. Similar eicosapentaenoic acid and docosahexaenoic acid plasma levels achieved with fish oil or krill oil in a randomized double-blind four-week bioavailability study. Read 2026-10-22.
- Vosskötter F, et al. Lipids 2023. Equal bioavailability of omega-3 PUFA from Calanus oil, fish oil and krill oil: A 12-week randomized parallel study. Read 2026-10-22.
- Kim MG, et al. Nutr Rev 2020. Lipid-modifying effects of krill oil vs fish oil: a network meta-analysis. Read 2026-10-22.
- Huang H, et al. Diabetes Metab Syndr 2023. Clinical effectiveness of krill oil supplementation on cardiovascular health in humans: an updated systematic review and meta-analysis of randomized controlled trials. Read 2026-10-22.
- Salem N Jr, Kuratko CN. Lipids Health Dis 2014. A reexamination of krill oil bioavailability studies. Read 2026-10-22.
- NHS. Fish and shellfish in your diet. UK. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.