Metabolic . Patient guide

Omega-3 Index Blood Test

What is Omega-3 Index

The Omega-3 Index is the combined percentage of EPA and DHA (the two long-chain omega-3 fatty acids) in red blood cell membranes. It is the most accurate single marker of long-term omega-3 status and an independent cardiovascular and cognitive health indicator.

This biomarker entry is being clinically reviewed by our team. The factual content draws on UK guidance (NICE, NHS, Royal Colleges and the relevant speciality society where cited).

Reference range

Reported in %. Final reports always carry the issuing laboratory's range, which is what your clinician will interpret against.

Group Range Note
High cardiovascular risk under 4 % of total fatty acids
Intermediate risk 4 to 8  
Optimal over 8  
Very high (review supplementation) over 12  

What it is

EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are obtained from oily fish, fish oil supplements, algae oil, and to a small extent from conversion of plant alpha-linolenic acid. They are incorporated into cell membranes throughout the body where they influence inflammation, brain function, and cardiovascular health. The Omega-3 Index measures their combined percentage of total red cell membrane fatty acids.

Why a clinician would order it

The index is checked as part of premium wellness screening, in patients with cardiovascular risk factors, in cognitive or mood symptom assessment, in inflammatory conditions, and to confirm supplementation is achieving the intended status. Particularly useful in patients with mainly plant-based diets where direct EPA and DHA intake is minimal.

If your level is outside the range

Symptoms of low Omega-3 Index

  • Dry skin
  • Dry eyes
  • Brittle nails
  • Mood symptoms
  • Difficulty concentrating
  • Symptoms are non-specific and often only diagnosed by testing

What low can indicate. Inadequate dietary intake of oily fish (UK recommendation is two portions weekly, one oily), reliance on plant-source omega-3 only (poor conversion of ALA to EPA and DHA), no supplementation in patients who do not eat fish.

Symptoms of high Omega-3 Index

  • Bruising tendency (high dose supplementation)
  • Mild blood thinning effect

What high can indicate. Regular oily fish intake plus high-dose supplementation. Not clinically harmful at typical supplemental doses but worth knowing if surgery is planned (some surgeons request reducing intake 7-14 days pre-operatively).

Testing tips

No fasting required. Reflects long-term intake (8 to 12 weeks of dietary pattern), not recent meals, so a single test is informative regardless of what you ate that morning. Repeat after 12 weeks of any dietary or supplement change to see the effect.

Where you can get this tested

Omega-3 Index is included in the following WMG Health panels. Same-day appointments at our Harley Street clinic, with results clinician-reviewed.

General Wellness
£279
View panel

Want a specific combination of markers we do not have a panel for? Build a custom panel and our clinicians will design one for you.

Symptoms often investigated with Omega-3 Index

Omega-3 Index is commonly tested when patients present with the following symptoms. If any of these resonate with you, the linked guides explain what to look for and which test pathway is appropriate.

Stress-Related Hair Loss: Testing the Real Drivers Severe stress can trigger heavy shedding 2 to 4 months later. Testing identifies the nutritional and thyroi... Read symptom guide → Hair Loss After COVID-19 or a Viral Illness Heavy shedding 2 to 4 months after COVID-19 is well documented (a viral telogen effluvium). A targeted pane... Read symptom guide → Erectile Changes: Blood Work That Matters Erectile changes can be vascular, hormonal or medication-related. A blood panel rules out the metabolic and... Read symptom guide → Perimenopause: Symptoms and When to Test Hot flushes, irregular cycles, sleep disruption and mood change can begin years before menopause. FSH, oest... Read symptom guide → Menopause: Symptoms and Bloodwork Context Menopause is diagnosed clinically (12 months without a period). Bloodwork has a role in younger women (unde... Read symptom guide → Thyroid Symptoms: When and What to Test Fatigue, weight change, hair loss, cold intolerance and mood change can all be thyroid driven. A full TSH, ... Read symptom guide →

Related markers

Glycated Haemoglobin (HbA1c) Metabolic

Sources

UK guidance our clinicians use when interpreting this marker.

This page is general patient information, not personal medical advice. A GMC-registered clinician will review your results and tailor any interpretation to you. See our Editorial Policy for how we write and review content.

Common questions about Omega-3 Index

What is a normal Omega-3 Index range?

High cardiovascular risk: under 4 (% of total fatty acids). Intermediate risk: 4 to 8. Optimal: over 8. Very high (review supplementation): over 12. Always interpret your own results against the laboratory range printed on your report, since assay-specific reference ranges vary.

What does a low Omega-3 Index result mean?

Inadequate dietary intake of oily fish (UK recommendation is two portions weekly, one oily), reliance on plant-source omega-3 only (poor conversion of ALA to EPA and DHA), no supplementation in patients who do not eat fish.

What does a high Omega-3 Index result mean?

Regular oily fish intake plus high-dose supplementation. Not clinically harmful at typical supplemental doses but worth knowing if surgery is planned (some surgeons request reducing intake 7-14 days pre-operatively).

Do I need to fast or prepare for the Omega-3 Index blood test?

No fasting required. Reflects long-term intake (8 to 12 weeks of dietary pattern), not recent meals, so a single test is informative regardless of what you ate that morning. Repeat after 12 weeks of any dietary or supplement change to see the effect.

Can I order a Omega-3 Index blood test privately in London?

Yes. WMG Health offers Omega-3 Index as part of bespoke panels and several pre-built panels at our 134 Harley Street clinic. Results are clinician-reviewed by a GMC-registered doctor within 4 hours for the most common assays. All panels are custom-built around your specific question; bookings via /contact/ or 020 3239 3378.