Omega-3 Index
EPA+DHA proportion in red blood cell membranes as a cardiac risk biomarker
Also known as
Definition
The Omega-3 Index is the proportion of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) relative to total fatty acids in red blood cell membranes, expressed as a percentage. It reflects long-term (3-month) omega-3 status and is recognized as a reliable marker of cardiovascular risk. Developed by Harris & von Schacky (2004), it is an independent cardiovascular risk marker alongside LDL and blood pressure.
| Parameter | Value |
|---|---|
| Unit | % |
| Reference Range | < 4% (risk zone) | 4–8% (intermediate zone) | > 8% (target range) |
| Optimal Range (lab2go) | > 8% (lab2go Optimum Zone; > 8% associated with lowest cardiovascular risk in Harris/von Schacky data) |
↓ What a low value means
An Omega-3 Index < 4% corresponds to a risk zone with elevated risk of myocardial infarction and sudden cardiac death (comparable to smoking as a risk equivalent according to von Schacky). Further associations: cognitive impairment, depressive symptoms, elevated inflammatory markers, dry eyes, joint inflammation.
↑ What a high value means
An index > 8% is the target range and indicates good EPA+DHA status. Values > 12% result from very high fish oil doses. Very high omega-3 levels can influence platelet function — clinically relevant only with concurrent anticoagulant therapy.
✓ How to optimize this marker
Dietary sources: fatty cold-water fish (salmon, mackerel, herring, sardines) 2×/week. Supplementation: 1–3 g EPA+DHA daily raises the index by ~3–4 percentage points (individual variability is large). Algae oil is a vegan alternative with comparable bioavailability to fish oil. Triglyceride form is better absorbed than ethyl ester form.
When to test
Annually with known heart disease, family cardiac risk, depression, cognitive decline, or to verify supplementation success. The erythrocyte test reflects the 3-month average — ideally measured 8 weeks after starting or changing supplementation.
Frequently asked questions
What is the difference between the Omega-3 Index and plasma omega-3? +
Plasma fatty acids reflect intake over the past 1–2 days (short-term status). The Omega-3 Index measures EPA+DHA in red blood cell membranes, which live 3 months — making it a long-term marker analogous to HbA1c for blood glucose. The erythrocyte index is more valid for cardiovascular risk assessment.
How much fish oil do I need to raise my Omega-3 Index above 8%? +
This is highly individual (genetics, BMI, baseline level). On average, raising the index from 4% to 8% requires ~2–3 g EPA+DHA daily over 3–4 months. A follow-up measurement is recommended because individual responses vary widely. Algae oil is equally effective.
Is algae oil as effective as fish oil? +
Yes. Algae oil contains preformed EPA and DHA (just like fish oil — fish accumulate omega-3 by eating algae). Studies show comparable bioavailability and comparable Omega-3 Index increases. Algae oil is more sustainable, free from contaminant residues, and is the vegan alternative.
Does a high Omega-3 Index actually protect against heart attack? +
Observational studies consistently show lower cardiovascular event rates with a high Omega-3 Index. REDUCE-IT (icosapent ethyl, high-dose EPA) showed significant reduction in cardiovascular events in high-risk patients. The preventive benefit appears strongest in those with a low baseline index.
Sources
Last Reviewed: May 28, 2026 · sina
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.