Omega-3 Index (EPA+DHA)
Shows how much of the fat in your red blood cells is the marine omega-3s EPA and DHA, a long-term picture of your fish and omega-3 intake.
AI-verified against cited sources. Awaiting expert reviewAlso called O3ILOINC 88998-0
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What it is
EPA and DHA are omega-3 fats found in fatty fish and in fish or algae oil supplements. They become part of the membranes of your red blood cells. The Omega-3 Index is the share of EPA and DHA among all the fatty acids in those membranes. Red blood cells live about four months, so it reflects your intake over that stretch, not just the last meal.
Why it matters
Higher levels of EPA and DHA in the blood are linked to a lower risk of heart disease and early death in large studies. These studies show a link, not proof that raising your level protects you. Surveys of healthy adults often find levels of 4% or less in North America and Europe, though individual results vary widely. The target test providers use is 8% or more.
If it’s low
A lower result usually means you are not eating much fatty fish or taking omega-3 supplements. This is very common, and it is not a diagnosis. Surveys of healthy adults in North America and Europe often find levels of 4% or less.
Common causes
- Little or no fatty fish in the diet
- No omega-3 supplement
- A vegetarian or vegan diet without an algae-based EPA and DHA source
- Higher body weight, which can mean a smaller rise from the same intake
What can help
- Eat more fatty fish, such as salmon, or ask a clinician whether an EPA and DHA supplement fits your health and medicines
- Give changes about 3 to 5 months before judging them with a repeat test
If it’s high
A result at or above 8% is in the target zone used by test providers. It usually means you eat a lot of fatty fish or take omega-3 supplements. No upper limit has been agreed on, and a higher number is not necessarily better.
Common causes
- Eating fatty fish often
- Taking fish oil, krill oil or algae oil supplements
- A traditional diet rich in seafood
What can help
- Review any omega-3 supplement and its dose with a clinician, especially if you take other medicines
If this applies to you
Omega-3 Index means a little more for some people. Open the one that fits you.
Tracking for long-term health
A pooled analysis of 17 cohort studies linked higher blood levels of EPA and DHA, the two omega-3 fats this test adds up, with a lower risk of death. It measured them in red cells or plasma rather than reporting the omega-3 index by name, and as an observational study it can't rule out that higher levels partly reflect a healthy lifestyle.
Vegan or vegetarian
Vegetarians eat less EPA and DHA, and vegans usually get almost none from food, so blood and tissue levels can be lower than in meat-eaters. The Academy notes that what this means for health is unknown.
What can affect your result
- How often you eat fatty fish and whether you take EPA and DHA supplements
- Body weight, age, sex and activity level, which change how much the index rises with a given intake
- Time: the index moves slowly, over about 3 to 5 months
- The blood fraction measured: red cells, plasma and whole blood give different numbers
- Sample type and lab, such as dried blood spot versus venous red cells
- Fish oil, krill oil and algae oil supplements and regular fatty fish raise the index; the change builds up over months, not days.
- Plasma or whole-blood EPA+DHA measured by another lab is not the same as the red-blood-cell index, so results are not interchangeable.
- Finger-prick dried-blood-spot kits and venous red-cell samples are both used; make sure you compare like with like over time.
About 3 to 5 months of steady intake for red blood cells to turn over and reflect a change; a dose-response trial used about 5 months.
When to talk to a clinician
A low Omega-3 Index is not an emergency. Talk with a clinician if you have heart disease, are on blood thinners or other medicines, are pregnant, or are thinking about starting a high-dose supplement.
Questions you could ask
- How should I weigh this result alongside my cholesterol, blood pressure and family history?
- Is my current omega-3 supplement still a good fit with my other medicines?
- What would be a realistic way for me to get more EPA and DHA?
- When should we recheck this after I make a change?
Questions people ask
Where does the 8% target come from?
A 2004 research paper found that people with an index of 8% or more had the lowest risk of fatal heart disease and those at 4% or less had the highest. It is a research-based goal, not a formal medical guideline, and the evidence is observational.
How long does it take to raise my Omega-3 Index?
Red blood cells take about four months to turn over, so expect around 3 to 5 months of steady intake before a retest shows the full effect. The size of the rise depends on how much EPA and DHA you take in and on factors like body weight.
Is my plasma or whole-blood EPA+DHA the same thing?
No. The 8% target is for red blood cells. Plasma and whole-blood values run differently, so a number from another kind of fatty acid test cannot be compared directly with the Omega-3 Index.
Show the science and sources
For clinicians and researchers
The Omega-3 Index is red blood cell EPA (20:5n-3) plus DHA (22:6n-3) as a percent of total identified fatty acids (OmegaQuant). Harris and von Schacky (2004) proposed it as a risk marker for death from coronary heart disease, finding the greatest cardioprotection at 8% or more and the least at 4% or less. In the Framingham Offspring cohort (n=2,500), the top quintile (above 6.8%) versus the bottom (below 4.2%) had a 34% lower risk of death from any cause and 39% lower risk of incident cardiovascular disease. A pooled analysis of 17 cohorts (FORCE, 42,466 people) found 15 to 18% lower all-cause mortality in the top versus bottom quintile of long-chain omega-3 levels. A global survey converted blood fractions to red-cell equivalents and found levels above 8% in places such as the Sea of Japan and Scandinavia and 4% or less across North America, Europe and much of the world. In a randomized dose-response trial (Flock, 2013), the index rose with EPA+DHA dose over about 5 months, and body weight, baseline index, age, sex and physical activity helped explain the response. These are observational associations for the index itself; randomized trials of omega-3 supplements have given mixed results for heart outcomes. Plasma phospholipid, whole-blood and red-cell EPA+DHA are not interchangeable.
LOINC 88998-0 (primary), 90911-9. Specimen: red-blood-cells.
Sources
- The Omega-3 Index: a new risk factor for death from coronary heart disease?, Preventive Medicine (2004)
- Omega-3 Index Complete, OmegaQuant
- Blood n-3 fatty acid levels and total and cause-specific mortality from 17 prospective studies, Nature Communications (2021)
- Erythrocyte long-chain omega-3 fatty acid levels are inversely associated with mortality and with incident cardiovascular disease: The Framingham Heart Study, Journal of Clinical Lipidology (2018)
- Global survey of the omega-3 fatty acids, docosahexaenoic acid and eicosapentaenoic acid in the blood stream of healthy adults, Progress in Lipid Research (2016)
- Determinants of erythrocyte omega-3 fatty acid content in response to fish oil supplementation: a dose-response randomized controlled trial, Journal of the American Heart Association (2013)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.