Marker · Ranges for learning, not a diagnosis
Omega-3 index
Also called EPA plus DHA percent, RBC omega-3.
How much of the fat in your red blood cells is EPA and DHA, the two main fish oil fats. It shows how much oily fish or fish oil you take in. It does not diagnose heart disease.
Read this first
- Coach, not doctor. Aaron Cuha is a coach, not a doctor. No medical credential is claimed for him, or for these pages. A number on a blood test is something to talk over with a doctor, not something to diagnose yourself with. Nothing here is a prescription, a plan to follow, or a reason to start or stop a medicine. Educational use only. This database summarizes published research and is not medical advice. Where a dose appears it is a record of what a trial or clinic ran, or what people describe doing, with its source attached. Nothing here is a recommendation for personal use.
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Why a longevity audience asks
Harris first suggested it as a number to talk about heart risk. Later, pooled studies that followed people over time still linked a higher index to fewer deaths from heart disease. But big studies that gave people high-dose omega-3 had mixed results. So the index tells you about your food and capsules. It is not a promise that raising it prevents heart attacks.
How a coach reads it
The owner's published target on /supplements is 8 to 10 percent. The papers that introduced the index called about 8 percent and above the good range, and under 4 percent the high-risk range. Those ranges come from research papers. They are not a diagnosis. Your lab's own normal range is the one your doctor reads.
Units on this page: percent of red-cell fatty acids
When it is low
Usually means you eat little oily fish and are not taking much fish oil. It does not, by itself, say you will have a heart attack.
When it is high
Usually means your diet or capsules are working. In big studies, high-dose EPA raised real questions about an irregular heartbeat (atrial fibrillation). That is one to talk over with a doctor, not a reason to chase a higher number forever.
Easy ways to misread it
- EPA and DHA in the liquid part of blood (plasma) is not the same test as the red blood cell index.
- A fish oil capsule is not icosapent ethyl, the prescription drug. The REDUCE-IT study tested the drug, so its results do not carry over to the bottle on the shelf.
- Do not start or stop a statin, a blood thinner, or any heart medicine because of this number.
What to ask your doctor
Ask for an omega-3 index, or red blood cell EPA and DHA. Say if you already take fish oil, so the blood draw is timed fairly.
Related supplements
Related when-playbooks
Sources on this page
- The Omega-3 Index: a new risk factor for death from coronary heart disease?
Harris and von Schacky introduce the index as a number to talk about heart risk.
2004PMID 15208005 - The omega-3 index as a risk factor for coronary heart disease.
Harris describes the index again as a sign of risk, not a treatment target you set yourself.
2008PMID 18541601 - The Omega-3 Index and relative risk for coronary heart disease mortality: Estimation from 10 cohort studies.
Pooled studies that watched people over time. Nobody was given anything. Whether raising the index helps is a different question.
2017PMID 28511049