What Are the Signs You Need Omega-3? What Low Intake Looks Like

There is no reliable sign that you need omega-3. Low intake of EPA and DHA produces no symptom you can feel, the NHS has no test for it, and the online checklists (dry skin, brittle nails, poor concentration, aching joints, low mood, dry eyes) list things that have commoner causes. The everyday guide is oily fish: most UK adults eat less than the one portion a week the NHS advises, and people who eat no fish, vegans in particular, sit lowest.^{1, 2, 3} Look at your plate, not your fingernails.

• Symptoms: none is specific; each has a commoner cause and a proper test
• Likely to be low: no oily fish, vegan or vegetarian, pregnant or breastfeeding
• The fix: two portions of fish a week, one oily, or an algal DHA source, read in milligrams

Sources checked on 29 October 2026.

What are the signs you need omega-3?

What are the symptoms of omega-3 deficiency?

True essential fatty acid deficiency is rare and looks nothing like the lists: a scaly rash, poor wound healing and slow growth in infants, seen almost only in people fed intravenously without fat.⁴ Nobody on a mixed diet, vegan included, develops it: ALA is plentiful in plant foods. A fish-free diet produces low status instead: EPA and DHA were "low but stable" in 659 British men, lower in vegetarians and vegans than in meat-eaters and no lower after twenty years on the diet than after one.³

How do you know if you are lacking omega-3?

SACN's population figure is about 450 mg of EPA and DHA a day, which two portions of fish a week, one oily, supply; without oily fish the rest of the diet gives a few tens of milligrams.⁵ If you cannot remember your last portion of oily fish, your intake is below the UK guideline, like most of the country's: the National Diet and Nutrition Survey finds oily fish intake below one 140 g portion a week in every age group.²

Can I test my omega-3 levels at home? (the omega-3 index)

Yes, privately, by finger-prick. The omega-3 index is the share of red blood cell fatty acids that is EPA plus DHA. Its proposers tied 8% or more to the lowest risk of coronary death and 4% or below to the highest, and a 2016 survey of 298 studies placed the UK, with most of Europe and North America, in that lowest band.⁶ These are associations. The NHS does not offer the test, so you interpret it yourself: it reflects three to four months of intake, and a low result in a non-fish-eater is expected.

Who is most likely to be low?

• Anyone who eats no oily fish. A few tens of milligrams against the 250 mg of EPA and DHA behind the register's heart wording is the whole story.^{5, 7}
• Vegans and vegetarians. In 165 long-term vegans the mean index was 3.7%; 254 mg a day of algal EPA and DHA for four months raised it from 3.1% to 4.8% in those below 4%.⁸ ALA alone does not make up the shortfall: about 5% becomes EPA and under 1% DHA.⁹ Does flaxseed oil contain omega-3, 6 and 9 has the detail.
• Pregnancy and breastfeeding. The baby draws DHA from the mother, so the register adds 200 mg a day of DHA to the adult 250 mg.⁷ In a large trial, omega-3 reduced early preterm birth only in women who started with low omega-3 status, from 3.2% to 0.7%.¹⁰

Do the symptoms people search for respond to omega-3?

Mostly not, so none was a sign of low omega-3.

• Dry eyes. 3 g of EPA and DHA a day for a year was no better than olive oil on symptoms or signs in 535 people.¹¹
• Low mood. In diagnosed depression, omega-3 added to usual care gave a small-to-moderate benefit in the Cochrane review, about 2.5 points where 3 is the smallest change patients notice, at very low certainty; in 18,353 adults without depression, 1 g of fish oil a day for five years did not lower the number of new cases, which were slightly more frequent on omega-3.^{12, 13}
• Joints. In rheumatoid arthritis, 2.7 g or more a day for three months reduced painkiller use: a prescription-level amount, not a label dose; for osteoarthritis, what is the best joint supplement sets out the evidence.¹⁴
• Skin. Dry skin rests on two small 12-week flaxseed-oil trials (omega 3-6-9 for hair and skin has them); the Cochrane review of eczema found no convincing evidence for any supplement.¹⁵
• Concentration. Across 38 trials and 49,757 adults, omega-3 made no or very little difference to cognitive scores.¹⁶ Is omega-3 good for your brain has the detail.

What depletes omega-3 in the body?

Status follows intake: the index is a rolling four-month average of what you ate, falling when fish or supplements stop and rising when they restart. Linoleic acid (omega-6) competes with ALA for the same enzymes; in the British vegetarian and vegan men, plasma DHA was lower the higher their plasma linoleic acid.³ Alcohol, stress, caffeine and "toxins" do not appear in the evidence.

How long does it take to correct a low omega-3 level?

Plasma responds within two weeks, red cells over months: 600 mg of DHA a day from algal-oil capsules or cooked salmon raised plasma DHA by about 80% in a fortnight, and the vegan trial took four months.^{17, 8} Should omega-3 be taken daily explains why the trials dosed daily for years.

How to raise your omega-3 intake

Fish first: at least two portions a week, one oily.¹ If fish is off the menu, algal oil is the direct route to DHA, read against the register's yardsticks above.^{7, 17} Algae omega-3 vs fish oil compares them. A vegan omega-3 gummy supplies tens of milligrams of algal DHA per serving, read against that 250 mg. For ALA, two tablespoons of ground flaxseed or 25 g of chia or walnuts reach the 2 g a day behind the register's cholesterol wording;^{7, 18} a flaxseed-oil omega 3-6-9 capsule supplies ALA, with linoleic and oleic acid, and no EPA or DHA. How much omega 3-6-9 do I need daily has the label-reading table; the Wellgard omega-3 guide the full picture. How to get enough omega-3 on a vegan diet covers the plant route, and why fish oil is no longer recommended the dose question.

What we don't know

The large trials dosed by the milligram, not to an index target, so none shows that lifting a 4% index to 8% changes outcomes.⁶ Whether supplementing women with already high omega-3 status raises early preterm birth is unresolved.¹⁰

Frequently asked questions

Does the NHS recommend omega-3 supplements?

Not for the general population: the advice is food, two portions of fish a week including one oily, and to avoid fish liver oil supplements in pregnancy because of their vitamin A.¹

What vitamin are you lacking if you have dry eyes?

Usually none. Dry eye is mostly tear evaporation; the NHS approach is lid care and drops, and omega-3 at 3 g a day was no better than placebo in the largest trial.¹¹

How can you tell if you're low on omega-3 without a test?

By intake: no oily fish most weeks, or a vegan or vegetarian diet without an algal source, meant low EPA and DHA status in the studies that measured it.^{3, 8} Is there any danger when taking omega-3 covers the opposite question.

Sources

1. NHS. Fish and shellfish. Page last reviewed 26 June 2026. nhs.uk.
2. NDNS: results from years 9 to 11 (2016 to 2019). Published 11 December 2020. gov.uk.
3. Rosell MS, et al. Long-chain n-3 fatty acids in plasma in British men. American Journal of Clinical Nutrition, 2005. Cross-sectional study, 659 men; funding not stated on PubMed. PubMed 16087975.
4. Gramlich L, et al. Essential fatty acid deficiency in 2015. JPEN Journal of Parenteral and Enteral Nutrition, 2015. Review and case series; funding not stated on PubMed. PubMed 26187936.
5. SACN. Advice on fish consumption: benefits and risks. Published 1 December 2004. gov.uk.
6. Harris WS, von Schacky C. The Omega-3 Index. Preventive Medicine, 2004. Proposal paper; funding not stated on PubMed. PubMed 15208005; Stark KD, et al. Global survey of blood DHA and EPA. Progress in Lipid Research, 2016. 298 studies; funding not stated on PubMed. PubMed 27216485.
7. Great Britain nutrition and health claims (NHC) register. Page last updated 19 May 2026. gov.uk.
8. Sarter B, et al. Blood DHA and EPA in vegans. Clinical Nutrition, 2015. 165 vegans, 46 supplemented for 4 months; funding not stated on PubMed. PubMed 24679552.
9. Plourde M, Cunnane SC. Extremely limited synthesis of long chain polyunsaturates in adults. Applied Physiology, Nutrition, and Metabolism, 2007. Review; funding not stated on PubMed. PubMed 17622276.
10. Simmonds LA, et al. Baseline omega-3 status and early preterm birth. BJOG, 2020. Exploratory randomised-trial analysis; funding not stated on PubMed. PubMed 32034969.
11. Asbell PA, et al. n-3 fatty acid supplementation for dry eye disease (DREAM). New England Journal of Medicine, 2018. Placebo-controlled trial, 535 patients, 12 months; publicly funded (NIH). PubMed 29652551.
12. Appleton KM, et al. Omega-3 fatty acids for depression in adults. Cochrane Database of Systematic Reviews, 2021. 33 placebo-controlled trials, 1,848 adults; non-commercial funding. PubMed 34817851.
13. Okereke OI, et al. Marine omega-3 fatty acids and risk of depression (VITAL-DEP). JAMA, 2021. Placebo-controlled trial, 18,353 adults aged 50 and over, median 5.3 years; publicly funded (NIH). PubMed 34932079.
14. Lee YH, et al. Omega-3 fatty acids and the treatment of rheumatoid arthritis. Archives of Medical Research, 2012. Meta-analysis, 10 trials, 370 patients; funding not stated on PubMed. PubMed 22835600.
15. Bath-Hextall FJ, et al. Dietary supplements for established atopic eczema. Cochrane Database of Systematic Reviews, 2012. 11 trials, 596 people; no conflicts declared. PubMed 22336810.
16. Brainard JS, et al. Omega-3, omega-6 and polyunsaturated fat for cognition. Journal of the American Medical Directors Association, 2020. Meta-analysis, 38 trials, 49,757 adults, 24 weeks or longer; funding not stated on PubMed. PubMed 32305302.
17. Arterburn LM, et al. Algal-oil capsules and cooked salmon. Journal of the American Dietetic Association, 2008. Open-label randomised trial, 32 adults, 2 weeks; lead author employed by the manufacturer. PubMed 18589030.
18. Public Health England. Composition of foods integrated dataset (CoFID). Page last updated 19 March 2021. gov.uk.

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This article is general information, not medical advice. If you have symptoms that worry you, are pregnant or breastfeeding, or take an anticoagulant or other regular medicine, speak to your GP or pharmacist before adding an omega-3 supplement.