Overview
Quick answer
The omega-3 index is the share of your red blood cell fatty acids that are EPA and DHA, the long-chain omega-3 fats found mainly in oily fish and other seafood (Harris and von Schacky 2004). It reflects intake over months, not your last meal. In Australia you can measure it with a finger-prick dried blood spot kit.
In the research that proposed the index, 8% or more was linked with the greatest protection from death from coronary heart disease and 4% or less with the least. These are research cut-offs, not an Australian clinical target. Supplement trials have found little or no effect on cardiovascular events, so treat the number as information to discuss with a clinician.
Overview
At a glance
- What it measures
- EPA plus DHA as a % of red blood cell fatty acids (Harris and von Schacky 2004)
- What it reflects
- Your intake over months, not your last meal
- Research cut-offs
- 8% or more: greatest cardioprotection. 4% or less: least (Harris and von Schacky 2004)
- Sample
- A finger-prick dried blood spot, collected at home
- Fasting
- Not needed for the kits sold in the Hemexa shop
- Turnaround
- 3 to 5 working days from receipt of the sample (Fatty Acid Labs website)
- Where to get it
- Three finger-prick kits in the Hemexa shop. Create an account or sign in to see prices
Overview
Key takeaways
The omega-3 index is EPA plus DHA as a percentage of the total fatty acids in your red blood cells, so it is reported as a % rather than in mmol/L.
Red blood cell fatty acids reflect your usual intake over months, so the result describes your habits rather than a single meal.
In the 2004 paper that proposed the index (Harris and von Schacky), 8% or more was linked with the greatest cardioprotection and 4% or less with the least, and the relationship is graded, so there is no cliff edge at either number.
A finger-prick dried blood spot estimates the index from fatty acids in whole blood using a conversion equation, whereas a venous sample can measure red blood cells directly.
Large observational studies link higher blood omega-3 levels with lower risk of death, but randomised trials of omega-3 supplements have found little or no effect on cardiovascular events overall, with a possible slight reduction in coronary heart disease events (low-certainty evidence).
The index changes slowly: a 2013 dose-response trial measured it after about five months, the time the researchers allowed for red cell fatty acids to reach a new steady state.
Basics
What the omega-3 index is
EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are long-chain omega-3 fats found predominantly in oily fish such as mackerel, herring, sardines, salmon and tuna, and in other seafood (NHMRC Nutrient Reference Values).
Harris and von Schacky proposed the omega-3 index in 2004 as a single number for this status: EPA plus DHA in red blood cell membranes, as a percentage of all red blood cell fatty acids. They argued that red blood cell fatty acid composition reflects long-term intake of EPA and DHA, and that the index may be a graded, modifiable risk factor for death from coronary heart disease.
A percentage
The result is EPA plus DHA as a share of all fatty acids in red blood cell membranes, so it is reported as a %, not in mmol/L.
Red blood cells
Their fatty acid make-up reflects long-term intake of EPA and DHA rather than your last meal (Harris and von Schacky 2004).
Food and supplements
Oily fish and EPA plus DHA supplements both go with a higher index. In a survey of 3,458 adults, supplement use went with 2.2 points higher (Jackson et al. 2019).
Jackson et al. 2019 reported two cross-sectional studies, of 28 and 3,458 adults. In both, each step up in reported fish intake went with an index 0.50 to 0.65 percentage points higher. Intake was self-reported, and most adults in the larger study were from the United States.
Method
How it is measured
The index is defined on red blood cells, so the most direct measurement is red blood cell fatty acids from a venous blood sample. A finger-prick kit collects a few drops of blood on a card, called a dried blood spot. The laboratory measures the fatty acids in that whole blood and uses a conversion equation to estimate the red blood cell value. A 2026 study of 595 Australian athletes used exactly this approach, with a validated conversion algorithm (Macartney et al. 2026).
The kits sold in the Hemexa shop are finger-prick kits from Fatty Acid Labs, posted to you. The kit contains a card to collect the blood on, two lancets to prick your finger, an antiseptic wipe and a prepaid return envelope. You collect the sample yourself at home and post it back at no charge, so there is no visit to a collection centre. You do not need to fast, although some other blood tests do (see the fasting blood test guide). Follow the other instructions that come with your kit.
Fatty Acid Labs, a brand of Masdiag Pty Ltd, analyses the samples by gas chromatography with flame ionisation detection. It says it converts dried blood spot measurements to red blood cell equivalent values with a validated correction factor (Fatty Acid Labs, Analytical Quality page). It states a turnaround of 3 to 5 working days from receipt of the sample, which does not include the time your sample spends in the post (Fatty Acid Labs website).
Dried blood spot
Done at home from a finger prick. The lab estimates the red cell value, so compare it with another dried blood spot result.
Venous sample
Measures red blood cell fatty acids directly. It needs a blood draw, which the Hemexa kits do not.
What is in the kit
- Collection card
- Two lancets
- Antiseptic wipe
- Prepaid return envelope
Reading your results
Reading your result
| Band | Index | What the source says | Source |
|---|---|---|---|
| Higher | 8% or more | Linked with the greatest protection from death from coronary heart disease in the original analysis. | Harris and von Schacky, Preventive Medicine 2004 |
| In between | More than 4% and less than 8% | Between the two ends. The relationship was described as graded, so risk was not treated as switching on or off at either number. | Harris and von Schacky, Preventive Medicine 2004 |
| Lower | 4% or less | Linked with the least protection from death from coronary heart disease in the original analysis. | Harris and von Schacky, Preventive Medicine 2004 |
| Described as desirable | 8% to 12% | A span some later papers call desirable, associated in those papers with better heart and brain health. | Jackson et al., Prostaglandins, Leukotrienes and Essential Fatty Acids 2019 |
Whose numbers these are
The 8% and 4% cut-offs come from the researchers who proposed the index. They are not an Australian clinical guideline, not a pathology reference interval and not a diagnostic threshold.
What the laboratory uses
The Fatty Acid Labs website describes the same three bands: below 4%, 4% to 8% and above 8%. Those are the laboratory's description of the index, not an Australian clinical guideline.
What the Heart Foundation sets
The National Heart Foundation of Australia gives an intake target rather than a blood level: 250 to 500 mg of marine omega-3s (EPA and DHA) per day, which it puts at about 2 to 3 serves of fish, including oily fish, per week. It says that for most people food sources are enough and that anyone considering a supplement should check with their doctor first (page last updated 17 June 2025).
What surveys find
A global review of 298 studies of healthy adults found very low levels (4% or less, in red blood cell equivalents) across much of North and South America, Europe, the Middle East, Southeast Asia and Africa, and high levels (above 8%) around the Sea of Japan, in Scandinavia and in populations not fully adapted to Westernised food habits (Stark et al. 2016).
The kits
What the kits report
Hemexa sells three Fatty Acid Labs finger-prick kits in its shop. They differ in what the laboratory reports.
Omega-3 Index
Your Omega-3 Index: EPA and DHA as a percentage of red blood cell fatty acids.
Omega-3 Plus Ratios
The Omega-3 Index plus the omega-6 to omega-3 ratio, the AA to EPA ratio and a trans fat index.
Omega-3 Complete
A full profile of 24 fatty acids, with the Omega-3 Index and its ratios.
AA is arachidonic acid, an omega-6 fat. The research cited on this page is about the Omega-3 Index, so its cut-offs apply to the index alone, not to the ratios or the trans fat index.
Limits
What it cannot tell you
It is a marker, not a diagnosis
A low index says your red blood cells carry little EPA and DHA. It does not say you have heart disease or that you will develop it, and a high index does not rule either out.
Association is not the same as a treatment effect
A pooled analysis of 17 prospective cohort studies (42,466 people, 15,720 deaths over a median of 16 years) found a 15 to 18% lower risk of death from any cause in the highest fifth of circulating long-chain omega-3 levels than in the lowest fifth (Harris et al. 2021). A Cochrane review of 86 randomised trials (162,796 people) of increased omega-3 intake found little or no effect on all-cause mortality (risk ratio 0.97, 95% confidence interval 0.93 to 1.01), cardiovascular mortality (0.92, 0.86 to 0.99, moderate-certainty evidence) or cardiovascular events (0.96, 0.92 to 1.01). It found a possible slight reduction in coronary heart disease events (0.91, 0.85 to 0.97, low-certainty evidence) (Abdelhamid et al. 2020). The two answer different questions: one compares people by their levels, the other tests what happens when intake is raised.
It informs a decision, it does not make one
Whether to change your diet or take a supplement is for you and your GP, dietitian or pharmacist, who know your history and your medicines. This page gives no dose.
One sample, one moment
The result describes your red blood cell fatty acids when the sample was taken. It says nothing about the rest of your diet, your cholesterol or your blood pressure, which are separate measurements.
The omega-3 index sits beside the markers that measure other parts of cardiovascular risk, not in place of them: LDL cholesterol and triglycerides, ApoB, hs-CRP and homocysteine each answer a different question.
Timing
Retesting
Retest timing follows the biology, not a calendar: the index changes slowly.
In a randomised, placebo-controlled trial of 115 healthy adults, people took 0, 300, 600, 900 or 1,800 mg of EPA plus DHA a day for about five months, the approximate time the researchers allowed for red cell fatty acids to reach a new steady state (Flock et al. 2013). The index rose in step with the dose, and no one taking 600 mg a day or less reached 8%.
A retest only a few weeks after a change in diet or supplements is therefore unlikely to show the full effect. Compare like with like: a dried blood spot result is best compared with another dried blood spot result.
The right gap differs by marker. For the others, see our how often blood tests guide.
The table below shows what happened in that trial. It describes one group of healthy adults and is not advice about what to take.
| EPA plus DHA a day | Average index after about five months | Change |
|---|---|---|
| 0 mg (placebo) | About 4.4% | No change from a baseline of about 4.4% |
| 300 mg | About 6.2% | Up about 1.9 points from a baseline of about 4.3% |
| 600 mg | About 6.8% | Up about 2.5 points from a baseline of about 4.3% |
| 900 mg | About 7.5% | Up about 3.2 points from a baseline of about 4.3% |
| 1,800 mg | About 9.5% | Up about 5.2 points from a baseline of about 4.3% |
How to get tested
How to get tested
The omega-3 kits are sold in the Hemexa shop. Create an account or sign in to see the kit prices, choose a kit and pay, and the kit is ordered from Fatty Acid Labs for you.
A home kit does not involve a pathology request form or a visit to a collection centre.
This guide covers the kits sold in the Hemexa shop. If you are unsure whether the test suits you, your GP, dietitian or pharmacist can talk it through with you.
Browse the other biomarker guides for the tests that sit alongside this one.
FAQ
Frequently asked questions
- What is the omega-3 index?
- The omega-3 index is the amount of EPA and DHA in your red blood cells as a percentage of all the fatty acids in those cells. Harris and von Schacky proposed it in 2004 as a measure of long-term omega-3 status and a possible risk factor for death from coronary heart disease.
- What should your omega-3 index be?
- In the research that proposed the index, 8% or more was linked with the greatest protection from coronary heart disease death and 4% or less with the least (Harris and von Schacky 2004). Some later papers describe 8% to 12% as desirable (Jackson et al. 2019). These are research cut-offs, not an Australian clinical target, so ask your clinician how to read your own result.
- How do I test my omega-3 index?
- You can use a finger-prick dried blood spot kit, from which the laboratory estimates the index, or a venous blood sample analysed for red blood cell fatty acids. The finger-prick kit is collected at home and posted back, with no visit to a collection centre.
- Where can I get an omega-3 index test in Australia?
- You can order a finger-prick omega-3 index kit in the Hemexa shop: Omega-3 Index, Omega-3 Plus Ratios and Omega-3 Complete, made by Fatty Acid Labs and posted to you. Create an account or sign in to see prices and choose a kit.
- Is an omega-3 index test worth it?
- It depends on what you would do with the number. The index gives a measured view of your own omega-3 status rather than an estimate from what you remember eating. But trials of omega-3 supplements have found little or no effect on cardiovascular events overall, with a possible slight reduction in coronary heart disease events (low-certainty evidence), and the test cannot say whether you should change anything.
- How often should I retest my omega-3 index?
- The index changes slowly, so give a change time to show. A supplement trial measured it after about five months, the time the researchers allowed for a new steady state. A retest only weeks after a change is unlikely to show the full effect.
- How much does an omega-3 index test cost in Australia?
- Prices vary by provider and by kit. Hemexa shows the price of each of its three omega-3 kits in the shop once you create an account or sign in, so this guide does not print a figure that could go out of date.
- Do I need to fast for an omega-3 index test?
- No. You do not need to fast for the omega-3 index kits sold in the Hemexa shop. The index reflects your intake over months rather than your last meal (Harris and von Schacky 2004). Follow the other collection instructions that come with your kit.
- What is the difference between a finger-prick test and a blood draw?
- The index is defined on red blood cells. A venous blood draw can measure red blood cell fatty acids directly, while a finger-prick dried blood spot is whole blood from which the laboratory estimates the red cell value with a conversion equation. Compare results from the same method over time.
- Can I take omega-3 if I am taking rivaroxaban?
- Rivaroxaban is an anticoagulant, and whether an omega-3 supplement suits you alongside it is a medical question this guide cannot answer. Talk to your GP or pharmacist before you start or change any supplement.
- Does the test tell me whether to take fish oil?
- No. It measures a level. It does not say whether a supplement would help you, and this guide does not recommend a dose. Whether to change your diet or take a supplement is a conversation for your GP, dietitian or pharmacist.
Sources
References
Harris WS, von Schacky C. The Omega-3 Index: a new risk factor for death from coronary heart disease? Preventive Medicine 2004;39(1):212-220. View source ↗
Flock MR, Skulas-Ray AC, Harris WS, Etherton TD, Fleming JA, Kris-Etherton PM. Determinants of erythrocyte omega-3 fatty acid content in response to fish oil supplementation: a dose-response randomized controlled trial. Journal of the American Heart Association 2013;2(6):e000513. View source ↗
Harris WS, Tintle NL, Imamura F, et al. Blood n-3 fatty acid levels and total and cause-specific mortality from 17 prospective studies. Nature Communications 2021;12:2329. View source ↗
Abdelhamid AS, Brown TJ, Brainard JS, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews 2020;3:CD003177. View source ↗
Stark KD, Van Elswyk ME, Higgins MR, Weatherford CA, Salem N. Global survey of the omega-3 fatty acids, docosahexaenoic acid and eicosapentaenoic acid in the blood stream of healthy adults. Progress in Lipid Research 2016;63:132-152. View source ↗