Last week, we explored the origin of the Omega-3 Index, created by Dr. Bill Harris and Dr. Clemens von Schacky. This week, we’ll look at what makes the Omega-3 Index test unique compared to other omega-3 blood tests—and why it’s considered the most reliable measure of omega-3 status.
Backed by Science and Research
The Omega-3 Index from OmegaQuant is the only omega-3 blood test supported by hundreds of published studies. Over the past 15 years, it has been used in research across more than 100 institutions worldwide, establishing itself as the gold standard biomarker for omega-3 levels.
When you take this test, you can trust that your results are not just numbers—they reflect meaningful insights into your long-term health.
Red Blood Cells vs. Plasma: Why It Matters
Blood is made up of two main components:
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Plasma (fluid portion) – about 60% of total volume
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Red blood cells (RBCs) – about 40% of total volume
Most omega-3 tests measure EPA and DHA levels in plasma, but the Omega-3 Index is based on red blood cells. Why? Because RBCs provide a more stable and reliable marker of long-term omega-3 intake, while plasma levels fluctuate depending on your most recent meal.
In early validation studies, Dr. Harris and his colleagues showed that while plasma omega-3s correlated with red blood cell levels, they were far more variable. By contrast, RBC omega-3 content reflects average intake over the past 3–4 months, making it a truer measure of nutritional status.
3 Reasons the Omega-3 Index Is Superior
1. More Stable and Reliable Results
In a 6-week study, Dr. Harris measured omega-3 levels in both plasma and RBCs from volunteers who made no lifestyle changes. Plasma EPA/DHA levels varied by about 16%, while RBC levels varied by only 4%.
This lower variability means the Omega-3 Index is a consistent marker, similar to how HbA1c reflects average blood sugar over time. You can’t “game” the test by taking fish oil the night before—it reflects months of intake, not hours.
2. Stronger Correlation with Tissues
Omega-3s matter because of how they integrate into tissues like the heart, brain, and joints. In a study of heart transplant patients, researchers compared omega-3 levels in RBCs with those in heart tissue. The correlation was strong: higher RBC levels meant higher heart tissue levels.
This confirms that the Omega-3 Index truly reflects omega-3 status throughout the body—not just in circulation.
3. Resistant to Short-Term Spikes
Other omega-3 tests based on plasma can be misleading. For example, if you take a large fish oil dose right before a test, plasma omega-3 levels can jump 30% in just a few hours. But your Omega-3 Index won’t change, because RBCs don’t respond to acute spikes.
This makes the Omega-3 Index a trustworthy long-term marker, unaffected by short-term fluctuations.
The Dose-Response Relationship
To test whether the Omega-3 Index truly reflects intake, Dr. Harris conducted a dose-response study. Participants took different daily doses of EPA + DHA (0, 300, 600, 900, and 1800 mg) for five months.
The results were clear: the higher the intake, the higher the Omega-3 Index. This confirmed that the test accurately tracks omega-3 consumption over time.
Why the Omega-3 Index Matters
The Omega-3 Index gives you something other omega-3 tests cannot:
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Stability – Reflects long-term intake, not just recent meals
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Accuracy – Correlates with actual tissue levels
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Predictive power – Higher Omega-3 Index levels are linked to lower cardiovascular risk
That’s why the Omega-3 Index has become the most trusted measure of omega-3 status in both research and clinical practice.
Final Thoughts
Not all omega-3 tests are created equal. By measuring omega-3 levels in red blood cells, the Omega-3 Index provides a stable, accurate, and meaningful marker of your nutritional status—one that reflects true long-term intake and health risk.
When it comes to assessing and improving your omega-3 levels, the Omega-3 Index is the tool doctors and researchers rely on—and the one you can trust.