Glossary term

Omega-3 index

Also known as RBC EPA+DHA index

RBC EPA+DHA percentage. The only magnesium-style marker that reflects long-term fatty acid status.

The Omega-3 index is the percentage of EPA and DHA out of total fatty acids in red blood cell membranes. It reflects several months of intake rather than the last meal, which is why it outperforms serum omega-3 as a cardiovascular risk marker. Below 4% is high risk, 4-8% is intermediate, 8%+ is the target. REDUCE-IT and follow-on data support the cardiovascular relevance of moving the index with 2 g/day EPA+DHA in high-risk subjects.

Unit

% EPA+DHA of total RBC fatty acids

Typical range

High risk < 4%; intermediate 4-8%; target ≥ 8% (Harris/von Schacky scale).

Medically reviewed byDr. Lena Okafor, MD

Medical Director - updated April 2026 - How we review