What is omega-3 index?
EPA and DHA are the two omega-3 fatty acids found mainly in oily fish: herring, mackerel, salmon, sardines. Your body hardly makes them itself, and what you take in is built into the wall of all your cells, where they keep the wall supple, dampen inflammation and play a role of their own in the heart and brain. A red blood cell lasts about four months, and the fatty acid composition of its wall is therefore an archive of what you ate in those months. The omega-3 index is the share of EPA and DHA in all the fatty acids of that wall, expressed in percent. It is a share, and that means two routes up and down: more or less EPA and DHA, but also more or less of the other fatty acids, because the division goes through the total. The index responds slowly: anyone who eats fish today sees that back only after weeks, and a change of habit shows fully after three to four months. The index is determined in red blood cells, not in the serum most blood values come from, and in the Netherlands no regular lab measures it; anyone who has it had it done at a foreign or non-certified laboratory. So there is no normal; what there is, is a target range of 8 to 12 % from research on the heart and vessels, with below 4 % as undesirable. Anyone who eats little fish usually sits around 4 %.
Why is omega-3 index relevant?
Unlike most nutritional values in blood, this index gives an average over months instead of a snapshot. That is why it exists: a fatty acid in the serum moves with your last meal, the share in the cell wall with your habit. Anyone who wants to know whether they take in enough omega-3 gets the most honest answer here. The second reason is the link with the heart and vessels. In large population studies people with a high index had less chance of sudden cardiac death and of cardiovascular disease in general, and the target range of 8 to 12 % comes from that work. EPA and DHA lower the triglycerides, keep the heartbeat more regular and dampen inflammation in the vessel wall. Two portions of oily fish a week is what the Dutch dietary guidelines recommend for that reason. The honest limitation is that the index is mainly a research measure. In the Netherlands nobody measures it, the author who published the target range has interests in a laboratory that offers the test, and the studies of fish oil as a supplement show smaller effects than those of fish in the diet. So read the index as a measure of your fish intake over months, and leave the question of whether your heart is healthy to your blood pressure, LDL, triglycerides and fitness.
Omega-3 index decision limits
What counts beside the number:
- How often you eat oily fish or take fish oil, because that is almost always the explanation
- How much sunflower oil and processed food you eat, because the omega-6 fatty acids from those take up the place in the wall
- Your triglycerides, because they fall with more EPA and DHA
- Which laboratory did the measurement, because no Dutch lab measures the index and the methods are not standardised
- How long ago your habit changed, because the wall of a red blood cell renews over three to four months
- Your blood pressure, LDL and fitness, because those determine your vascular risk and the index alone does not
There is no Dutch band for the omega-3 index, because no regular, certified laboratory in the Netherlands measures it; Unilabs writes that itself beside its determination and draws no blood for it. What does exist comes from research: a target range of 8 to 12 % and an undesirable value below 4 %, both from Harris et al., 2019, established in an American cohort and not in a Dutch population. A review by the same author from 2025 carries a conflict-of-interest statement: he holds stock in a laboratory that offers fatty acid testing, this index included. Reference points then, not a diagnosis, and your own previous measurement from the same laboratory is the best benchmark.
Omega-3 index high or low: what it means
A low index means there is little EPA and DHA in your cell walls. Usually it is the first and rarely the last: little oily fish in your diet, because your body hardly makes these fatty acids itself and one portion a month is too little to fill the wall; and more of the other fatty acids, especially the omega-6 fatty acids from sunflower oil and processed food, which take up the place in the wall and lower the share without less omega-3 having come in. Anyone who eats little fish usually sits around 4 %, and that is the undesirable side. A high index means a lot of EPA and DHA in the wall, and that is the favourable side: more oily fish or fish oil in your diet, because the wall fills over months with what you take in, and less of the other fatty acids, so the share rises without more omega-3 having come in. Above 12 % the research says nothing more; there is no upper limit with a published meaning, but there is also no reason to aim higher. What you do about it: eat oily fish twice a week, herring, mackerel, salmon or sardines, because that lifts the index to the target range in three to four months. If that does not work, fish oil or algae oil with EPA and DHA does the same, at a dose of about a gram a day; linseed and walnuts provide a different omega-3 fatty acid that the body converts only in small part. At the same time replace sunflower oil and processed food with olive oil, so the other fatty acids take up less room. The index belongs beside your triglycerides, which fall with more EPA and DHA, beside your HDL and LDL, which the question of your vascular risk works on, and beside your previous index from the same laboratory, because the measurement is not standardised and the value changes slowly.
What lowers it
Little EPA and DHA in the cell wall, and that almost always comes from the diet.
| Cause | How often |
|---|---|
| Less EPA and DHA in your foodYour body hardly makes these fatty acids itself; anyone who rarely eats oily fish usually sits around 4 % | Often |
| More of the other fatty acidsThe share is divided by all fatty acids together, so a lot of omega-6 from sunflower oil and processed food lowers it without less omega-3 having come in | Sometimes |
What raises it
A lot of EPA and DHA in the cell wall, and that is the favourable side.
| Cause | How often |
|---|---|
| More EPA and DHA in your foodTwo portions of oily fish a week or fish oil fill the wall over months; the healthy route to the target range | Often |
| Less of the other fatty acidsA smaller total below the line lifts the share without more EPA or DHA having come in, for instance after replacing sunflower oil with olive oil | Sometimes |
How does an omega-3 index blood test work?
- Referral
- Not possible by the usual route: in the Netherlands no regular, certified laboratory measures the index. Anyone who wants to know it has it done at a foreign or non-certified laboratory, often with a finger prick on a card.
- Fasting
- Not needed. The index is an average over months, so what you ate on the day itself does not determine the share.
- When
- When you want to know whether your fish intake is enough, and again three to four months after a change in fish or fish oil, because before that the cell wall has not yet renewed.
- The draw
- A few drops of blood from a finger prick or a tube from a vein; the index is determined in the red blood cells and not in the serum.
- Repeating
- Once a year, or three to four months after a change in your diet. Compare only with a previous measurement from the same laboratory, because the methods differ.
- Where to draw
- You can draw at 250+ locations near you, no referral needed. See the locations
Frequently asked questions
What is the omega-3 index?
The percentage of EPA and DHA in the wall of your red blood cells. EPA and DHA are the two omega-3 fatty acids from oily fish. Because red blood cells last for months, the index reflects your intake over that period and not your last meal. No Dutch lab measures it; anyone who has it had it done at a foreign or non-certified laboratory.
What is a healthy omega-3 index?
An index of 8 to 12 %, the target range from research on the heart and vessels by Harris et al. from 2019; below 4 % that same study calls undesirable, and in between lies the intermediate zone. Anyone who eats little fish usually sits around 4 %. It is not a laboratory band and was not established in a Dutch population, so read your result as a position on that scale.
What does a low omega-3 index mean?
That there is little EPA and DHA in your cell walls, and that almost always comes from eating little oily fish: your body hardly makes these fatty acids itself. A lot of sunflower oil and processed food lower the share further, because the omega-6 fatty acids from those take up the place in the wall. Two portions of oily fish a week or fish oil lifts the index to the target range in three to four months.
What does a high omega-3 index mean?
That your cell walls contain a lot of EPA and DHA, and that is the favourable side: you regularly eat oily fish or take fish oil. Above 12 % the research the target range comes from says nothing more; there is no upper limit with a published meaning, but there is also no reason to aim higher.
What do I do about a low index?
Eat oily fish twice a week: herring, mackerel, salmon or sardines. If that does not work, fish oil or algae oil with EPA and DHA does the same, at a dose of about a gram a day. Linseed and walnuts provide a different omega-3 fatty acid that the body converts only in small part, so they hardly lift the index. At the same time replace sunflower oil with olive oil. Measure again only after three to four months.
Which Dutch laboratory measures the omega-3 index?
No regular laboratory at all. Unilabs, the only one of the four large labs that carries the determination in its catalogue, writes beside it that no regular, certified laboratory is known in the Netherlands that can determine the concentration, that a non-certified laboratory in Bunnik does, and that no blood is drawn or forwarded for it. The other three do not carry the determination.
Where does the target range of 8 to 12 % come from?
From research on the heart and vessels. Harris et al. write in 2019 that the omega-3 index is inversely linked to the risk of cardiovascular disease and that 8 to 12 % is the protective range. In that same study, in more than two thousand Americans, only a handful sat within that range and more than four in ten below 4 %. The same author holds stock in a laboratory that offers the test, and that belongs with it when you read the boundary.
How quickly does the omega-3 index change?
Slowly. The index looks at the share of EPA and DHA in the wall of your red blood cells, and a red blood cell lasts about four months. The result is therefore an average over months instead of a snapshot, and a repeat is only useful after three to four months of changed intake.
Which tests include omega-3 index?
Omega-3 index is part of Advanced, the broader panel. It is not orderable yet.
Related biomarkers
Read on
Sources
- 1.Harris WS, Jackson KH, Brenna JT et al., Survey of the erythrocyte EPA+DHA levels in the heart attack/stroke belt, Prostaglandins, Leukotrienes and Essential Fatty Acids. 2019. pubmed.ncbi.nlm.nih.gov
- 2.Harris WS, Recent studies confirm the utility of the omega-3 index, Current Opinion in Clinical Nutrition and Metabolic Care. 2025. pubmed.ncbi.nlm.nih.gov
- 3.Unilabs, test catalogue (Dutch): Omega-3. 2026. bepalingenklapper.nl
Educational information only, not medical advice. Consult a healthcare professional for clinical decisions.
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Omega-3 index is part of Advanced, the broader panel. It is not orderable yet.
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