The Omega-3 Index Test: Where the 8% Target Comes From, Who Built It, and What Trials Say About Raising It
The Omega-3 Index is a finger-prick test that reports how much EPA and DHA sits in your red blood cells. Here is what the number means, the observational studies behind the 8% target, the commercial ties behind the test, and why pushing the number up with fish oil has not clearly cut major cardiovascular events in a large trial.
By Kymata Health Editorial Published Last checked
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From a partner brand · paid link
Momentous Omega-3, 60 softgels
from Momentous
Label: 2 softgels: 800 mg EPA and 800 mg DHA.
Best for regular use: $29.99 on subscription vs $39.99 one-time (checked Oct 8, 2026).
Key takeaways
From 9 sources- The Omega-3 Index is EPA plus DHA as a percentage of the fatty acids in red blood cell membranes; its creators proposed 8% or more as the lowest-risk level and 4% or less as the highest14.
- In 17 cohorts with 42,466 people, those in the top fifth for blood omega-3 had a 15% to 18% lower risk of death than the bottom fifth. That is an association, not proof that supplements help3.
- Fish oil moves the number in a dose-dependent way, and body weight matters; in one trial, 0.88 g of EPA plus DHA a day took the index from 6.0% to 8.9% in 6 months56.
- In VITAL, a large trial of 1 g a day in adults at usual risk, major cardiovascular events did not drop significantly, and across trials doses above 1 g a day were linked to more atrial fibrillation78.
- The test’s lead developer holds stock in a lab that sells blood fatty-acid testing. The research is peer-reviewed, but the conflict is worth knowing3.
What this article covers
2 evidence profilesThe evidence, graded
Pulled from the trial tables in our evidence profiles. Grades follow our evidence-grading policy.
Graded findings
3 rows- ∅No effectHeart and blood-vessel events at 1 g/day (VITAL)No effect Major cardiovascular events HR 0.92 (95% CI 0.80–1.06) and invasive cancer HR 1.03; neither significant. Secondary: total myocardial infarction HR 0.72 (0.59–0.90). No excess bleeding.Omega-3 (fish oil, krill oil, algal oil) · RCT · n=25,871 · 2019 · PMID 30415637
- AGrade AIrregular heart rhythm riskWorsened Omega-3 was associated with more atrial fibrillation (HR 1.25). Risk was higher in trials using >1 g/day (HR 1.49) than ≤1 g/day (HR 1.12); each extra 1 g/day raised the HR by about 11%.Omega-3 (fish oil, krill oil, algal oil) · Meta-analysis · n=81,210 · 2021 · PMID 34612056
- CGrade CKnee pain, stiffness and functionImproved Pain, stiffness and function improved modestly more than placebo; the Omega-3 Index rose from 6.0% to 8.9%.Krill oil · RCT · n=235 · 2022 · PMID 35880828
Safety at a glance
From our Omega-3 (fish oil, krill oil, algal oil) evidence profilePublished interactions and cautions only. Each one is cited on our Omega-3 (fish oil, krill oil, algal oil) evidence profile, with its own numbered sources.
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.
- Anticoagulants or antiplatelet drugs
- Omega-3 acids may prolong bleeding time; the prescription label advises periodic monitoring when combined.
Who should be careful
- Atrial fibrillation or high cardiovascular risk
- Pooled outcome trials link omega-3 supplements to more atrial fibrillation; a 2026 analysis of 35 trials found the rise only in people at high cardiovascular risk taking more than 1.5 g/day. The prescription label notes more AF recurrences in people with existing AF.
- 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.
- 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.
- Pregnancy and breastfeeding
- A Cochrane review of 70 trials (19,927 women) found omega-3 in pregnancy lowered preterm birth (RR 0.89) and early preterm birth (RR 0.58), with more pregnancies past 42 weeks. ODS lists 8–12 oz/week of lower-mercury seafood (FDA, ACOG) and an ALA AI of 1.4 g in pregnancy and 1.3 g while breastfeeding; it sets no separate breastfeeding limit for EPA/DHA supplements.
What the Omega-3 Index measures
The index is the share of EPA and DHA, the long-chain omega-3s in fish and fish oil, among all fatty acids in red blood cell membranes4. Red-cell fatty acid makeup reflects long-term EPA and DHA intake rather than your last meal1.
It was proposed in 2004 by William Harris and Clemens von Schacky as a risk factor for death from coronary heart disease. Pulling together lab work and published prevention studies, they found an index of 8% or more was associated with the greatest protection and 4% or less with the least1.
A 2024 global map using the same metric grouped countries as very low (4% or less), low (above 4% to 6%), moderate (above 6% to 8%) and desirable (above 8%)4. Most countries were low or very low; the United States moved from very low to low compared with the 2016 map4.
Not every omega-3 blood test reports this exact number. The map’s authors had to use conversion equations to turn plasma and whole-blood results into an estimated red-cell index4, so check which metric your report uses before comparing it with the 8% target.
The evidence behind the 8% target
The strongest support is observational. In the Framingham Offspring cohort (2,500 people, mean age 66, median follow-up 7.3 years), people in the top fifth of the index (above 6.8%) had a 34% lower risk of death from any cause and a 39% lower risk of heart and blood-vessel disease than those in the bottom fifth (below 4.2%)2. Notice that even the top fifth started below 8%2.
A pooled analysis of 17 prospective cohorts followed 42,466 people for a median of 16 years, during which 15,720 died3. After adjustment, the highest versus lowest fifth for circulating EPA, DPA and DHA had a 15% to 18% lower risk of death, with similar patterns for heart disease, cancer and other causes3.
Studies like these cannot rule out that people with high omega-3 levels differ in other ways, such as diet, income or overall health. They show who tends to do well, not what happens when you take a supplement to change the number.
Who is behind the test
Much of the Omega-3 Index research comes from one group, and the disclosures are public:
- In the 17-cohort analysis, William Harris declared stock in OmegaQuant Analytics, a lab that offers blood fatty-acid testing, as a competing interest related to the work3.
- The Framingham paper lists Harris’s affiliation with OmegaQuant Analytics2.
- The 2024 world map was written with authors from the Fatty Acid Research Institute and the Global Organization for EPA and DHA Omega-3s, an industry trade group4.
- In the dose-response trial below, Harris disclosed that he was president of OmegaQuant and had consulted for companies including Amarin and GlaxoSmithKline; the trial itself was funded by a USDA grant, with capsules donated by Nordic Naturals5.
- The krill oil trial that raised the index from 6.0% to 8.9% was supported by Swisse Wellness, which helped design it6.
How much omega-3 moves the number
A randomized trial gave 115 healthy adults 0, 300, 600, 900 or 1,800 mg of EPA plus DHA a day for about 5 months5. The index rose with dose, and dose alone explained 68% of the variation in response; adding baseline index, age, sex and physical activity explained 78%5. Dose per kilogram of body weight explained 70%, slightly more than dose alone, so body weight matters when you compare your result with someone else’s5.
In a 6-month trial in 235 adults with knee osteoarthritis, 4 g of krill oil a day (0.60 g EPA and 0.28 g DHA) raised the index from 6.0% to 8.9%, while placebo stayed near 5.5%6. Our fish vs krill vs algae oil guide covers how the forms compare at matched doses.
A better number has not clearly meant fewer heart events in trials
The VITAL trial randomized 25,871 US adults at usual risk to 1 g a day of marine omega-3 or placebo for a median of 5.3 years. Major cardiovascular events were not significantly reduced (hazard ratio 0.92, 95% CI 0.80 to 1.06), and cancer was unchanged7. Total heart attacks, a secondary end point, were lower (hazard ratio 0.72), a finding the trial was not designed to confirm7.
Higher doses carry a rhythm signal. A meta-analysis of 7 trials with 81,210 people found omega-3 supplements were linked to more atrial fibrillation (hazard ratio 1.25), with a larger effect in trials using more than 1 g a day (1.49)8. Our fish oil after 50 guide covers that trade-off in detail.
Put together: the index is a good marker of how much EPA and DHA you eat, and low levels travel with worse outcomes in cohort studies. What has not been shown is that taking capsules to hit the target lowers your own risk7.
If you test anyway
A test can tell you whether your intake is low and whether a change in diet or dose is moving the number. A few practical points:
What it costs a month: supplements priced at the studied dose, beside their evidence grade, in Evidence per Dollar.
- Compare like with like: red-cell index results and plasma or whole-blood omega-3 results are different metrics4.
- Retest after months, not weeks; the dose-response trial measured after about 5 months5.
- On warfarin or another anticoagulant: NIH notes fish oil might raise INR with warfarin, although most research at 3 to 6 g a day found no significant effect on anticoagulation9. Tell your prescriber either way.
- History of atrial fibrillation: the rhythm signal was strongest above 1 g a day8, so dose decisions belong with your cardiologist.
- Ordering your own labs? Our blood-testing hub compares direct-to-consumer services, and our omega-3 page covers doses and forms.
Quick answers
Common questions
4 answersWhat is a good Omega-3 Index?
How long does it take to raise the Omega-3 Index?
Is every omega-3 blood test an Omega-3 Index?
No. Some tests measure plasma or whole blood rather than red cells, and researchers need conversion equations to compare them with the red-cell index4.
Keep reading
Full evidence profiles
Every graded study, studied doses, interactions and safety- Fatty acidOmega-3 (fish oil, krill oil, algal oil)Omega-3 supplements supply the long-chain fatty acids EPA and DHA from fish oil, krill oil or algae, or ALA from plant oils.AGrade A
- Fatty acidKrill oilKrill oil is an omega-3 oil from Antarctic krill; much of its EPA and DHA is bound to phospholipids, and it contains astaxanthin.BGrade B
Related articles
4 articles- ArticleFish Oil After 50: Big Trials Found No Drop in Heart Events, and a Heart-Rhythm Signal Nobody MentionsDoes fish oil protect the heart, and can it cause atrial fibrillation?
- ArticleFish Oil vs Krill Oil vs Algae Oil: Which Omega-3 Is Worth Your Money?Is krill oil better than fish oil, and is algae oil as good?
- ArticleHow Much Omega-3 Per Day? EPA and DHA Doses by Goal, From the TrialsHow much omega-3 (EPA and DHA) should I take per day?
- ArticleOmega-3 for Depression: A Small, EPA-Dependent Effect, and No Protection in a 5-Year TrialDoes omega-3 fish oil help with depression?
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Where to buy Omega-3 (fish oil, krill oil, algal oil)
Products from brands we partner with that contain Omega-3 (fish oil, krill oil, algal oil). Check the amount per serving against the doses studied, and the label for other ingredients.
Omega-3 (fish oil, krill oil, algal oil) products from partner brands
7 products Paid links · we earn a commission- Quick pickMomentousMomentous Omega-3, 60 softgelsWe use this brand at home. What we useSubscribe & save 25%
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Pick “Subscribe 25% Off” on the product page; delivery every 1, 2 or 3 months; cancel or reschedule anytime.
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2 softgels: 800 mg EPA and 800 mg DHA; 30 servings
$39.99one-time$29.99subscribeChecked Oct 8, 2026 - MomentousMomentous Vegan Omega-3, 60 capsulesWe use this brand at home. What we useSubscribe & save 25%
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Pick “Subscribe 25% Off” on the product page; delivery every 1, 2 or 3 months; cancel or reschedule anytime.
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- Our Momentous links apply the brand’s ambassador discount at checkout, so there is no code to type. Momentous sets any discount it applies; check the cart total before you pay.
- Offer terms from Momentous’ site, checked Oct 8, 2026. Offers can change; the brand's checkout is final.
2 capsules: 1,000 mg omega-3 from algal oil (Schizochytrium sp.) with 500 mg EPA and 500 mg DHA; 30 servings
$54.99one-time$41.24subscribeChecked Oct 19, 2026 - SupersmartSuper Omega 3 (fish oil)5% off with the Supersmart newsletterGet 5% off with the newsletter (paid link, opens in new tab)
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Sign up for the newsletter at the bottom of us.supersmart.com; Supersmart says the 5% discount is permanent.
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3 softgels: 1,500 mg fish oil with 950 mg omega-3 as triglycerides (465 mg EPA, 345 mg DHA); 30 servings
$27.00one-time$22.95subscribeChecked Oct 11, 2026 - HerbsProNOW Foods Omega-3, 200 Softgels
2 softgels: 2,000 mg fish oil concentrate with 360 mg EPA and 240 mg DHA
$14.98one-timeChecked Oct 14, 2026 - Dr. TobiasDr. Tobias Triple Strength Omega 3 Fish Oil (180 softgels)
2 softgels: 2,000 mg fish oil with 1,400 mg omega-3 (800 mg EPA, 600 mg DHA), enteric-coated
$39.99one-timeChecked Oct 14, 2026 - Sports ResearchSports Research Omega-3 Fish Oil from Wild Alaska Pollock, Triple Strength 1250 mg (90 softgels)Subscribe & Save 15% + free shipping
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Choose Subscribe & Save on the product page and pick a delivery interval; modify or cancel anytime.
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1 softgel: 690 mg EPA + 260 mg DHA (1,040 mg total omega-3, triglyceride form); 90 servings
$31.17one-time$26.49subscribeChecked Oct 16, 2026 - OnnitOnnit Krill Oil, 60 softgelsWe use this brand at home. What we use
CGrade C, limited (Grade C) 190 mg EPA plus DHA per serving, below the 0.5 to 5 g a day trials used (most large trials about 1 g).
Caution: Contains crustacean shellfish (krill).
2 softgels: 1 g krill oil providing 450 mg phospholipids and 240 mg omega-3 (130 mg EPA, 60 mg DHA), plus 200 mcg astaxanthin; 30 servings. Contains crustacean shellfish (krill).
$29.95one-timeChecked Oct 20, 2026
References
9 sources. Numbers in the text link here.
Sources cited in this article
9 sources- 1The Omega-3 Index: a new risk factor for death from coronary heart disease?Prev Med, 2004 · PMID 15208005
- 2Erythrocyte long-chain omega-3 fatty acid levels are inversely associated with mortality and with incident cardiovascular disease: The Framingham Heart StudyJ Clin Lipidol, 2018 · PMID 29559306
- 3Blood n-3 fatty acid levels and total and cause-specific mortality from 17 prospective studiesNat Commun, 2021 · PMID 33888689
- 4Omega-3 world map: 2024 updateProg Lipid Res, 2024 · PMID 38879135
- 5Determinants of erythrocyte omega-3 fatty acid content in response to fish oil supplementation: a dose-response randomized controlled trialJ Am Heart Assoc, 2013 · PMID 24252845
- 6Krill oil improved osteoarthritic knee pain in adults with mild to moderate knee osteoarthritis: a 6-month multicenter, randomized, double-blind, placebo-controlled trialAm J Clin Nutr, 2022 · PMID 35880828
- 7Marine n-3 Fatty Acids and Prevention of Cardiovascular Disease and Cancer (VITAL)N Engl J Med, 2019 · PMID 30415637
- 8Effect of Long-Term Marine ω-3 Fatty Acids Supplementation on the Risk of Atrial Fibrillation in Randomized Controlled Trials of Cardiovascular Outcomes: A Systematic Review and Meta-AnalysisCirculation, 2021 · PMID 34612056
- 9Omega-3 Fatty Acids: Fact Sheet for Health ProfessionalsNIH Office of Dietary Supplements, 2025
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. Product links on this page are paid partner links.