Omega-3 index: what it is, what it tells you and when it’s tested

The omega-3 index shows what share of the fats in your red blood cells is EPA and DHA, the two omega-3s from fish. It is given as a percentage. It reflects what you have eaten over the last few months, not just the last few days.

When it’s tested

GPs do not usually order it: it is asked for by people who want to know whether they eat enough fish, or by a doctor or dietitian following someone who takes supplements. Only a few specialised labs run it.

It is not a routine test. In studies, people with a higher index live longer on average and have less heart disease. But taking omega-3 supplements has had little or no effect on heart attacks and deaths. That is why the result rarely changes care.

That is why Rosa does not test it. Instead it looks at triglycerides, ApoB, LDL cholesterol and high-sensitivity CRP, which say more about your heart risk. Triglycerides are also the value omega-3s lower most.

What it tells you, and what it does not

It tells you how much EPA and DHA you have taken in over the last few months, from fish or supplements. It is steadier than omega-3s measured in plasma, which change with your last meal.

It does not say whether you have heart disease, or how high your risk is. Cholesterol, blood pressure, smoking and blood sugar answer that.

That is why it is read together with other tests:

Omega-3 index reference values

There is no range printed on every lab report, as there is for other tests. The thresholds from studies are used: up to 4% is low, and 8% or more is the level that studies link to the lowest heart risk.

Each lab uses its own method. To compare two results, use the same lab.

There is no established upper limit. But getting there with high-dose supplements has its own risks.

What your result means

Find the row for your result, as a percentage.

If your omega-3 index is low or high

Omega-3 supplements: what studies say

Supplements raise the omega-3 index and lower triglycerides. On heart attacks, strokes and deaths taken together, though, the effect in trials has been small or none. There may be a small benefit for coronary heart disease.

At high doses they raise the risk of atrial fibrillation, an irregular heartbeat. The higher the dose, the higher the risk.

If you are thinking of a supplement, or already take blood thinners, ask your doctor whether you need it and how much.

How to raise your omega-3 index

The simplest way is through your plate:

What can skew the result

The omega-3 index is stable, but a few things matter.

When to worry

The omega-3 index on its own is not a reason to see a doctor. Talk to your doctor if:

Frequently asked questions

What is the omega-3 index? It is the percentage of EPA and DHA, the omega-3s from fish, among all the fats in your red blood cells. It reflects the last few months of eating.

What is a good omega-3 index? In studies, up to 4% goes with the highest heart risk and 8% or more with the lowest. There is no established upper limit.

Where can I get an omega-3 index test? Not at every lab. Only some specialised labs offer it: ask your lab or your doctor.

Do omega-3 supplements help? They raise the index and lower triglycerides, but in trials they did little for heart attacks and deaths. At high doses they raise the risk of atrial fibrillation. Decide with your doctor.

Does Rosa test the omega-3 index? No. Rosa measures triglycerides, ApoB, LDL cholesterol and high-sensitivity CRP, which say more about your heart risk.

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