Evidence explainerOmega-3 (fish oil, krill oil, algal oil)

Fish Oil vs Krill Oil vs Algae Oil: Which Omega-3 Is Worth Your Money?

Krill is sold as the premium option and algae as the vegan one. When researchers matched the actual EPA and DHA, the differences mostly disappeared. The label number that matters is not the one on the front.

By Kymata Health editorial teamPublished October 9, 2026Last reviewed October 9, 2026

Medical review pending. Written by our editorial team from the studies cited below; a credentialed clinician has not reviewed it yet. Educational only, not medical advice.

Key takeaways

  • When EPA and DHA were matched, a 4-week trial of 66 adults found no significant difference in blood EPA+DHA between krill oil and two fish oil forms [1].
  • Algal-oil capsules raised DHA as much as cooked salmon in a small 2-week trial (600 mg/day DHA) [2].
  • A typical 1,000 mg fish oil capsule provides about 180 mg EPA and 120 mg DHA, so read the EPA and DHA lines, not the oil weight [3].
  • Krill are crustaceans, so prescription omega-3 labels advise caution with shellfish allergy; algal oil is plant-derived [4][3].

Safety at a glance

From our Omega-3 (fish oil, krill oil, algal oil) monograph. Published interactions and cautions only, each with its source.

Interactions

  • Warfarin and similar anticoagulants. High-dose fish oil has antiplatelet effects and might raise INR with warfarin, although most research finds 3–6 g/day does not significantly change anticoagulation. Prescription omega-3 labels advise periodic monitoring.[1]
  • Anticoagulants or antiplatelet drugs. Omega-3 acids may prolong bleeding time; the prescription label advises periodic monitoring when combined.[9]

Who should be careful

  • Atrial fibrillation or high cardiovascular risk. Pooled outcome trials link omega-3 supplements to more atrial fibrillation, especially above 1 g/day, and the prescription label notes more AF recurrences in people with existing AF.[4][1][9]
  • Bleeding risk and surgery. Doses of 2–15 g/day EPA and/or DHA might lengthen bleeding time. Tell your surgeon or dentist, and your clinician if you take blood thinners.[1]
  • Fish or shellfish allergy. Fish oil and krill oil come from fish and crustaceans; prescription omega-3 labels advise caution with known fish or shellfish hypersensitivity. Algal oil is plant-derived.[9][1]
  • Pregnancy and breastfeeding. DHA matters in pregnancy. A Cochrane review cited by ODS found supplements slightly lengthened gestation and raised birth weight, with no consistent effects on other outcomes.[1]

Full Omega-3 (fish oil, krill oil, algal oil) safety section

The evidence, graded

Pulled from our monograph evidence tables. Grades follow our evidence-grading policy.

Three sources, two fatty acids

All three supply the long-chain omega-3s EPA and DHA. Fish oil comes as natural triglycerides, ethyl esters or re-esterified triglycerides; krill oil carries its omega-3s mainly as phospholipids; algal oil is mostly DHA in triglyceride form [3]. NIH notes that triglyceride and free fatty acid forms have somewhat higher bioavailability than ethyl esters, but all forms raise blood EPA and DHA [3].

Krill vs fish: the matched-dose test

Marketing for krill oil leans on its phospholipid form being absorbed better. The fair test is to give the same EPA and DHA from each source. A 2015 double-blind trial did exactly that: 66 healthy adults took 1.3 g/day of EPA+DHA from krill oil, fish oil ethyl ester or fish oil triglyceride for 4 weeks [1]. Plasma EPA+DHA did not differ significantly (p = 0.052), nor did red-cell levels, and bioavailability differed by less than 24% between products [1].

A smaller 12-person single-dose crossover found numerically higher uptake with krill, but the differences were not significant [5]. NIH summarizes the evidence as mixed [3]. Practically, krill capsules usually contain less EPA+DHA per serving, so you may need more capsules to match a fish oil dose [3].

Algae oil: the vegan route to DHA

In a 2008 trial, 32 healthy adults aged 20 to 65 got 600 mg/day of DHA either from algal-oil capsules or from cooked salmon for 2 weeks [2]. DHA rose about 80% in plasma phospholipids and about 25% in red cells in both groups, and the two were bioequivalent [2]. It was small and open-label, so we grade it D.

Algal oils mostly provide DHA, about 100 to 300 mg per serving, sometimes with some EPA [3]. If you want EPA specifically, check the label.

How to read the label

The big number on the front is often total oil. A typical 1,000 mg fish oil capsule provides about 180 mg EPA and 120 mg DHA, roughly 300 mg combined [3]. Compare products on EPA plus DHA per serving.

NIH reports that omega-3 supplements have not been found to contain methylmercury, which is removed during processing [3]. FDA has concluded that supplements providing no more than 5 g/day of EPA+DHA are safe when used as recommended [3].

Before you buy any of them

Large trials of about 1 g/day found no drop in major heart events, and pooled trials link omega-3 supplements to more atrial fibrillation; read fish oil and your heart before assuming more is better [6]. If you take warfarin or another blood thinner, check with your clinician first [4]. Full evidence is on the omega-3 monograph.

Quick answers

Is krill oil worth the higher price?

At matched EPA and DHA, a 4-week trial found similar blood levels with krill and fish oil [1]. Krill capsules usually hold less EPA+DHA per serving [3].

Does fish oil contain mercury?

NIH reports omega-3 supplements have not been found to contain methylmercury, because it is removed in processing and purification [3].

Keep reading

Full monographs

Related articles

Browse the full Supplement & Nutrient Encyclopedia or all supplement articles.

References

  1. [1]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. PMID 26328782
  2. [2]Algal-oil capsules and cooked salmon: nutritionally equivalent sources of docosahexaenoic acid. J Am Diet Assoc, 2008. PMID 18589030
  3. [3]Omega-3 Fatty Acids: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2025.
  4. [4]LOVAZA (omega-3-acid ethyl esters) capsule: prescribing information (Warnings 5.2, 5.3; Drug Interactions 7.1). DailyMed, U.S. National Library of Medicine, 2026.
  5. [5]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. PMID 21854650
  6. [6]Effect of Long-Term Marine ɷ-3 Fatty Acids Supplementation on the Risk of Atrial Fibrillation in Randomized Controlled Trials of Cardiovascular Outcomes: A Systematic Review and Meta-Analysis. Circulation, 2021. PMID 34612056

Omega-3 (fish oil, krill oil, algal oil) and other dietary supplements are not intended to diagnose, treat, cure or prevent any disease, and these statements have not been evaluated by the FDA. Talk to your clinician or pharmacist before starting a supplement, especially if you take prescription medicines. This page has no product or affiliate links.

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