Krill Oil vs Fish Oil: Which Should You Take?

Neither oil is proven better for health. Krill oil raised blood EPA and DHA about 1.5-fold more than fish oil in a 12-week trial of 72 adults¹, yet a dose-matched 4-week trial found no significant difference², and a network meta-analysis found their cholesterol and triglyceride effects do not differ³. Choose by the EPA plus DHA on the label and by shellfish allergy.

Both supply EPA and DHA, the long-chain fats on our omega-3 page⁴. Our krill oil page covers that supplement alone; this guide compares the two oils.

Not on the current evidence. For most goals, trials find similar results once the EPA and DHA doses are comparable^{3, 2}. The verdict by goal:

• Raising blood omega-3: mixed. Some trials favor krill oil, others find no difference (see the absorption section)^{5, 6}.
• Cholesterol and triglycerides: no significant difference in a network meta-analysis of 64 trials³.
• Knee osteoarthritis: krill oil did not beat placebo for pain in the largest trial, and we found no trial that compared it with fish oil⁷.
• Depression symptoms: both oils lowered scores versus placebo in 57 adults over 8 weeks, with no sign that either was superior⁸.
• Dry eye: both oils lowered tear osmolarity in 60 adults over 90 days, but only krill oil improved the symptom score versus placebo⁹.

Depression and dry eye each rest on one small head-to-head trial, and joints have none, so none of these is enough to name a winner.

They differ in chemical form, dose per capsule, source and extras:

• Form: krill oil carries most of its EPA and DHA in phospholipids, while fish oil carries them mainly in triglycerides¹⁰. Fish oil supplements are also sold as ethyl esters or re-esterified triglycerides⁴.
• Dose per capsule: in a 7-week trial, 3.0 g/day of krill oil supplied 543 mg of EPA plus DHA, while 1.8 g/day of fish oil supplied 864 mg¹¹. NIH says a typical 1,000 mg fish oil capsule has 180 mg EPA and 120 mg DHA, though doses vary widely⁴.
• Source: krill oil comes from the Antarctic marine crustacean Euphausia superba¹².
• Extras: krill oil contains astaxanthin; a 4 g/day dose supplied 0.45 g in one knee trial¹³.
• Contaminants: in a 2014 analysis of products sold in Australia, krill oils had intermediate levels of persistent organic pollutants compared with fish oil categories¹⁴.

Bioavailability, meaning how much EPA and DHA reaches your blood, differs between trials, and individual response varies widely¹⁰. Results by study:

• Single dose, 15 people, about 1,700 mg EPA plus DHA: krill oil gave a larger 72-hour rise in plasma phospholipid EPA and DHA than fish oil (89.08% vs 59.15%×h). Krill meal, which is also phospholipid-bound, matched fish oil, which argues against the phospholipid form as the reason¹⁰.
• Single dose, 12 men, 1,680 mg: krill oil ranked highest, but the differences were not significant. The krill product held 22% of its EPA as free EPA, which may have affected uptake¹⁵.
• 4 weeks, 24 adults, 600 mg omega-3: krill oil raised the omega-3 index (red blood cell EPA plus DHA) more than fish oil¹⁶.
• 4 weeks, 66 adults, 1.3 g/day EPA plus DHA in each arm: plasma EPA plus DHA was 118.5 ug/mL with krill oil vs 108 with fish oil triglycerides and 90.9 with ethyl esters, a gap that was not significant (p = 0.052)².
• 7 weeks, 113 adults: plasma EPA and DHA rose by similar amounts with both oils, though the krill dose of EPA plus DHA was 62.8% of the fish oil dose¹¹.
• 12 weeks, 62 adults, about 250 to 290 mg/day: the omega-3 index rose by 1.15 points with krill oil and 1.0 with fish oil, a comparable gain¹⁷.
• 12 weeks, 72 adults, 1.1 g/day: krill oil gave about 1.5-fold higher gains in plasma EPA and DHA than fish oil¹.

A 2024 network meta-analysis of 26 studies concluded that krill oil was better absorbed, especially below 2,000 mg, while noting high heterogeneity¹⁸. A 2025 review cautioned that large differences in single-dose studies often did not carry over to long-term supplementation⁶. An earlier review likewise found a probable difference in bioavailability but said more studies were needed before a firm conclusion⁵.

The practical reading: krill oil may need a somewhat lower EPA plus DHA dose to reach the same blood level. That is not the same as a proven health advantage.

Neither, according to the best head-to-head evidence. A network meta-analysis of 64 randomized trials found the net difference between krill oil and fish oil was not significant for triglycerides (weighted mean difference -4.07; 95% CI -15.22 to 7.08) or for LDL, HDL or total cholesterol³. It also found that each 1 g of omega-3 lowered median triglycerides by 8.971 mg/dL with fish oil and 9.838 mg/dL with krill oil³. The dose of omega-3 mattered more than the source.

Studies of krill oil alone also report lipid gains:

• A 2017 meta-analysis of 7 trials (662 participants) found krill oil lowered LDL by 15.52 mg/dL and triglycerides by 14.03 mg/dL, and raised HDL by 6.65 mg/dL¹⁹.
• A 2023 meta-analysis of 14 trials (1,458 participants) found lower total cholesterol, LDL and triglycerides, but no effect on blood pressure, blood sugar control or inflammatory markers²⁰.

Individual head-to-head trials are small and mixed. In 25 adults with moderately high triglycerides, fish oil ethyl esters (1,000 mg twice daily) lowered triglycerides more than krill oil (500 mg twice daily), but only krill oil raised HDL and apolipoprotein A-I and it lowered hs-CRP more²¹. In 24 healthy adults, total and LDL cholesterol rose after both krill and fish oil compared with corn oil¹⁶. In 113 adults, serum lipids did not differ between the two oils¹¹.

Both krill-oil meta-analyses say trials measuring heart attacks and deaths are still needed^{20, 19}. For triglycerides in particular, see our pages on krill oil for triglycerides and omega-3 for high cholesterol, and the wider heart health hub.

No trial has compared them head to head for joints, and krill oil's own results are mixed. In an Australian trial of 262 people with knee osteoarthritis and joint inflammation on MRI, 2 g/day of krill oil for 24 weeks did not reduce knee pain more than placebo (between-group difference -0.3 points on a 0 to 100 scale; 95% CI -6.9 to 6.4)⁷. An earlier 6-month trial of 235 adults with milder osteoarthritis used 4 g/day and found a small gain: knee pain improved 5.18 points more than placebo on the WOMAC scale (95% CI -10.0 to -0.32)¹³.

Pooled results lean cautious. A 2024 meta-analysis of 5 trials (700 patients) found no significant improvement in pain or stiffness and a small gain in physical function (SMD -0.24), concluding krill oil is not yet justified for knee pain²². A 2025 meta-analysis of 5 trials (730 participants) found WOMAC pain, stiffness and function gains but no change on the visual analog pain scale, and no difference in adverse events²³. For more on joints, see krill oil for osteoarthritis, omega-3 for joint pain, the joint health hub, or our glucosamine vs chondroitin comparison.

The head-to-head trials we found measured depression and dry eye, not memory or thinking skills. In 57 adults with major depressive disorder, krill oil (520 mg EPA plus DHA) and fish oil (600 mg) both lowered Hamilton depression scores versus placebo over 8 weeks, with no evidence that either was superior⁸. In 60 people with mild to moderate dry eye, both oils lowered tear osmolarity over 90 days (about -18.6 and -19.8 mOsmol/l vs -1.5 with placebo). The Ocular Surface Disease Index score fell more than placebo in the krill oil group only⁹.

We found no krill-versus-fish trial on thinking or memory⁸. For the wider evidence, see omega-3 for cognitive function.

The main drawbacks are allergy, drug interactions and a thinner head-to-head evidence base.

• Shellfish allergy: krill is a crustacean¹². An allergist's answer to the AAAAI on fish oil in shellfish-allergic patients says purification should remove allergen protein, but that this cannot be assured²⁴. That answer addresses fish oil, not krill oil, so someone with shellfish allergy should ask an allergist before trying krill oil.
• Blood thinners and surgery: a meta-analysis of 11 trials in 120,643 patients found no overall increase in bleeding (rate ratio 1.09; 95% CI 0.91 to 1.31). High-dose purified EPA raised the relative risk by 50%, an absolute increase of 0.6%²⁵. NIH notes that 2 to 15 g/day of EPA and DHA might lengthen bleeding time⁴. Our guide to blood thinners and supplements covers the wider picture.
• Warfarin: in a retrospective study of 573 warfarin users, the 145 taking fish or krill oil showed no significant change in time in therapeutic range or bleeding²⁶. NIH still advises people on anticoagulants to discuss omega-3 supplements with their clinician⁴.
• Everyday side effects: NIH lists unpleasant taste, bad breath, heartburn, nausea, stomach discomfort, diarrhea and headache for omega-3 supplements in general⁴. A review of 90 trials found higher odds of diarrhea (OR 1.257), altered taste (OR 3.478) and bleeding tendency (OR 1.260) with omega-3s, with no definite serious adverse events²⁷.
• Fish allergy: the AAAAI answer also describes a fish-allergic adult who developed chest tightness, shortness of breath and flushing after starting fish oil, and says it is unclear whether fish oil is safe in seafood allergy²⁴. Fish oil is not a safe default for someone allergic to finned fish.
• Heart rhythm at high doses: NIH reports that two large trials of 4 g/day of omega-3 for several years slightly raised atrial fibrillation risk in people with cardiovascular disease or high cardiovascular risk⁴. Discuss dose with your clinician if that describes you.
• Thin comparisons: few trials compare the two oils, and many use different EPA plus DHA doses⁵.

You can, but there is no reason to. We found no trial that tested the combination, so there is no evidence of added benefit. What counts is your total EPA plus DHA per day. NIH reports that the European Food Safety Authority and the FDA both judge supplement intakes of up to about 5 g/day of EPA plus DHA to be safe, while the Institute of Medicine set no upper limit⁴. Add the EPA plus DHA of both products together to see your true total.

Look at EPA plus DHA, not the oil weight. A 1,000 mg krill capsule does not hold 1,000 mg of omega-3: in one trial 3.0 g of krill oil held 543 mg of EPA plus DHA, about 18% of its weight¹¹.

Trials give a sense of what people tolerate. In the knee trial, 2 g/day for 24 weeks produced adverse events in 51% of the krill oil group and 54% of the placebo group⁷. The 4 g/day trial described krill oil as safe to consume over 6 months¹³. EFSA and the FDA put the safe ceiling for EPA plus DHA supplements at about 5 g/day, per NIH⁴, so 1,000 mg of krill oil is far below it. People with heart disease should note the atrial fibrillation signal at 4 g/day described above.

Use these decision rules:

• You have a shellfish allergy and tolerate finned fish: fish oil is the usual choice, but an allergist should confirm first, since the risk is very low but cannot be assured. If you are also allergic to fish, ask before either oil²⁴.
• You want to lower triglycerides: either works. Aim for the EPA plus DHA dose that trials used, because dose drives the effect³.
• You want a lower dose to raise your blood level: krill oil may get there at a lower EPA plus DHA dose, but the trials conflict^{1, 2}.
• You are looking for joint pain relief: neither has solid proof. The largest krill oil trial was negative⁷.

For timing, see our guide on when to take fish oil.

Supplements in this guide

• Krill Oil
• Omega-3 Fatty Acids
• Astaxanthin

We searched the research literature for head-to-head trials of krill oil and fish oil, meta-analyses of krill oil, and safety data, and read the NIH Office of Dietary Supplements omega-3 fact sheet and an AAAAI allergist's answer on fish oil. We prioritized randomized trials and systematic reviews in adults, and every journal record cited here was checked against PubMed on 2 November 2026. Head-to-head trials are small and use different doses, so the evidence cannot yet say whether krill oil has a health advantage.

1. Loukil I, et al. Krill oil increases plasma omega-3 fatty acids more than fish oil in healthy adults: a double-blind randomized controlled trial. Am J Clin Nutr. 2026;124(1):101346. doi:10.1016/j.ajcnut.2026.101346
2. Yurko-Mauro K, et al. Similar eicosapentaenoic acid and docosahexaenoic acid plasma levels achieved with fish oil or krill oil in a randomized double-blind four-week bioavailability study. Lipids Health Dis. 2015;14:99. doi:10.1186/s12944-015-0109-z
3. Kim MG, et al. Lipid-modifying effects of krill oil vs fish oil: a network meta-analysis. Nutr Rev. 2020;78(9):699-708. doi:10.1093/nutrit/nuz102
4. National Institutes of Health, Office of Dietary Supplements. Omega-3 Fatty Acids: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/
5. Ulven SM, et al. Comparison of bioavailability of krill oil versus fish oil and health effect. Vasc Health Risk Manag. 2015;11:511-24. doi:10.2147/VHRM.S85165
6. Alijani S, et al. Bioavailability of EPA and DHA in humans - A comprehensive review. Prog Lipid Res. 2025;97:101318. doi:10.1016/j.plipres.2024.101318
7. Laslett LL, et al. Krill Oil for Knee Osteoarthritis: A Randomized Clinical Trial. JAMA. 2024;331(23):1997-2006. doi:10.1001/jama.2024.6063 Our study summary.
8. Açik M, et al. The effect of fish oil versus krill oil intervention on clinical symptoms and cardiometabolic risk factors in patients with major depressive disorder: A randomized placebo-controlled double-blind trial. J Affect Disord. 2025;380:171-180. doi:10.1016/j.jad.2025.03.097
9. Deinema LA, et al. A Randomized, Double-Masked, Placebo-Controlled Clinical Trial of Two Forms of Omega-3 Supplements for Treating Dry Eye Disease. Ophthalmology. 2017;124(1):43-52. doi:10.1016/j.ophtha.2016.09.023
10. Köhler A, et al. Bioavailability of fatty acids from krill oil, krill meal and fish oil in healthy subjects--a randomized, single-dose, cross-over trial. Lipids Health Dis. 2015;14:19. doi:10.1186/s12944-015-0015-4
11. Ulven SM, et al. Metabolic effects of krill oil are essentially similar to those of fish oil but at lower dose of EPA and DHA, in healthy volunteers. Lipids. 2011;46(1):37-46. doi:10.1007/s11745-010-3490-4
12. Duo L, et al. Krill oil: nutraceutical potential in skin health and disease. Front Nutr. 2024;11:1388155. doi:10.3389/fnut.2024.1388155
13. Stonehouse W, et al. Krill oil improved osteoarthritic knee pain in adults with mild to moderate knee osteoarthritis: a 6-month multicenter, randomized, double-blind, placebo-controlled trial. Am J Clin Nutr. 2022;116(3):672-685. doi:10.1093/ajcn/nqac125 Our study summary.
14. Bengtson Nash SM, et al. A nutritional-toxicological assessment of Antarctic krill oil versus fish oil dietary supplements. Nutrients. 2014;6(9):3382-402. doi:10.3390/nu6093382
15. Schuchardt JP, et al. Incorporation of EPA and DHA into plasma phospholipids in response to different omega-3 fatty acid formulations--a comparative bioavailability study of fish oil vs. krill oil. Lipids Health Dis. 2011;10:145. doi:10.1186/1476-511X-10-145
16. Ramprasath VR, et al. 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. Lipids Health Dis. 2013;12:178. doi:10.1186/1476-511X-12-178
17. Vosskötter F, et al. Equal bioavailability of omega-3 PUFA from Calanus oil, fish oil and krill oil: A 12-week randomized parallel study. Lipids. 2023;58(3):129-138. doi:10.1002/lipd.12369
18. Pham TP, et al. Comparison of Omega-3 polyunsaturated fatty acids bioavailability in fish oil and krill oil: Network Meta-analyses. Food Chem X. 2024;24:101880. doi:10.1016/j.fochx.2024.101880 Our study summary.
19. Ursoniu S, et al. Lipid-modifying effects of krill oil in humans: systematic review and meta-analysis of randomized controlled trials. Nutr Rev. 2017;75(5):361-373. doi:10.1093/nutrit/nuw063
20. Huang H, et al. Clinical effectiveness of krill oil supplementation on cardiovascular health in humans: An updated systematic review and meta-analysis of randomized controlled trials. Diabetes Metab Syndr. 2023;17(12):102909. doi:10.1016/j.dsx.2023.102909
21. Cicero AF, et al. Lipid-lowering and anti-inflammatory effects of omega 3 ethyl esters and krill oil: a randomized, cross-over, clinical trial. Arch Med Sci. 2016;12(3):507-12. doi:10.5114/aoms.2016.59923
22. Pimentel T, et al. Krill oil supplementation for knee pain: a systematic review and meta-analysis with trial sequential analysis of randomized controlled trials. Inflammopharmacology. 2024;32(5):3109-3118. doi:10.1007/s10787-024-01543-7 Our study summary.
23. Meng J, et al. Krill oil for knee osteoarthritis: A meta-analysis of randomized controlled trials. Medicine (Baltimore). 2025;104(7):e41566. doi:10.1097/MD.0000000000041566 Our study summary.
24. American Academy of Allergy, Asthma & Immunology. Ask the Expert: Fish oil safety in a shellfish allergic patient (answered 4/20/2023). https://www.aaaai.org/allergist-resources/ask-the-expert/answers/2023/fishoil
25. Javaid M, et al. Bleeding Risk in Patients Receiving Omega-3 Polyunsaturated Fatty Acids: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. J Am Heart Assoc. 2024;13(10):e032390. doi:10.1161/JAHA.123.032390 Our study summary.
26. Pryce R, et al. The Use of Fish Oil with Warfarin Does Not Significantly Affect either the International Normalised Ratio or Incidence of Adverse Events in Patients with Atrial Fibrillation and Deep Vein Thrombosis: A Retrospective Study. Nutrients. 2016;8(9). doi:10.3390/nu8090578
27. Chang JP, et al. Safety of Supplementation of Omega-3 Polyunsaturated Fatty Acids: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Adv Nutr. 2023;14(6):1326-1336. doi:10.1016/j.advnut.2023.08.003