Is Omega-3 Worth Taking? The Evidence

Quick answer

Omega-3 fats from fish are a popular supplement, but big trials have disappointed for general heart health. Is omega 3 worth taking? A major review found that omega-3 supplements make little or no difference to deaths or cardiovascular events in most people [3]. The clearest effect is on triglycerides, a type of blood fat [3]. Higher doses have also been linked to a higher chance of an irregular heartbeat called atrial fibrillation [7]. We rate the evidence C: mixed, with benefits limited to particular outcomes. Oily fish is a simpler place to start.

What is omega-3?

Omega-3s are fats your body can’t make well itself. The two main “long-chain” types, EPA and DHA, come mostly from oily fish such as salmon, mackerel and sardines, and from fish oil and algae oil supplements [1]. The NHS advises at least 2 portions of fish a week, including 1 of oily fish [1]. In the US, the American Heart Association recommends 1 to 2 servings of seafood a week [11].

Is omega 3 worth taking? What it might help with

Possible benefit	Rating	In plain words
Lowering triglycerides (a blood fat)	Strong	About 15% lower on average, with bigger doses having more effect [3]
Heart attacks, strokes and deaths in the general population	No clear benefit	Little or no difference in a review of 86 trials [3] and in large trials [2][4]
Heart events in very high-risk people on a prescription omega-3 medicine	Mixed	One trial of a purified prescription drug was positive [6]; another using a different product was not [5]. These are medicines, not shop supplements
Mood and depression	No clear benefit	A large trial found no benefit [8]
Memory and thinking in middle age and older	Early	A review hints at a small benefit for “executive function” (planning and focus) [9]

Ratings describe how good the research is, not a promise that it will work for you.

What the research says

• Big review of 86 trials (162,796 people). Omega-3 supplements made little or no difference to death from any cause or to cardiovascular events (both high-certainty). Heart-disease events were slightly lower, with low certainty. Triglycerides fell by about 15% [3]. PubMed · DOI
• VITAL trial (US, 1 g a day). In adults with no earlier heart disease there was no clear drop in major cardiovascular events, and no extra bleeding [2]. PubMed · DOI
• ASCEND (15,480 people with diabetes, 1 g a day). No reduction in serious vascular events [4]. PubMed · DOI
• Heart rhythm. A 2021 review of 7 trials (81,210 people) linked omega-3 supplements to a higher risk of atrial fibrillation, especially above 1 g a day [7]. PubMed · DOI

Amounts and how people take it

These are amounts used in studies, not recommendations.

• Food first (US): the NIH Office of Dietary Supplements, summarizing American Heart Association advice, notes 1 to 2 servings of seafood a week. For pregnancy, US agencies advise 8 to 12 ounces a week of lower-mercury seafood [11].
• Food first (UK): the NHS suggests at least 2 portions of fish a week, one oily. Girls, women who may become pregnant, and pregnant or breastfeeding women should have no more than 2 portions of oily fish a week [1].
• Official intake figures: the US has no set amount for EPA and DHA (its Adequate Intake of 1.6 g for men and 1.1 g for women a day is for ALA, a plant omega-3) [11]. There is no formal US upper limit either, but the FDA says labels shouldn’t recommend more than 2 g a day of EPA plus DHA, and has concluded up to 5 g a day from supplements is safe [11].
• Typical capsule: see the label-reading section below [11].
• Supplement doses in big trials: about 1 g of omega-3 a day in VITAL and ASCEND [2][4]. Prescription products used 4 g a day [5][6].
• Forms: fish oil, or algae oil for people who avoid fish.

How to read an omega-3 label (EPA + DHA)

Look for the EPA and DHA amounts per serving, not just the “fish oil” total, because they are smaller. The NIH says a typical 1,000 mg fish oil capsule contains about 180 mg EPA and 120 mg DHA, though this varies widely [11]. Algae oil is an option if you avoid fish.

Prescription omega-3 vs fish oil supplements

• The prescription-drug exceptions. REDUCE-IT (8,179 high-risk people with high triglycerides) found fewer heart events with a purified prescription form of EPA, taken at 2 g twice a day. It also saw more hospital admissions for irregular heartbeat (3.1% vs 2.1%) [6]. PubMed · DOI STRENGTH (13,078 people, 4 g a day of a different product) found no benefit [5]. PubMed · DOI These drug results shouldn’t be assumed to apply to supplements.
• Supplement-dose trials. At about 1 g a day (VITAL and ASCEND), there was no clear drop in major cardiovascular events [2][4].

In short: the heart benefit seen with a purified prescription form of EPA at a high dose shouldn’t be assumed to apply to over-the-counter fish oil.

Omega-3 for mood and memory

• Depression. In 18,353 adults, omega-3 did not lower the risk of depression [8]. PubMed · DOI
• Memory. A 2024 review of 24 studies (9,660 people) suggested a possible benefit for executive function [9]. PubMed · DOI

Side effects, interactions and who should check first

Stomach upset is common and nosebleeds are uncommon, according to the prescribing information for a licensed omega-3 medicine [10]. Higher doses are linked to a higher chance of atrial fibrillation [7].

Who should check with a doctor or pharmacist first

Check with a doctor or pharmacist first if you:

• take blood thinners such as warfarin. High doses can slightly lengthen bleeding time, so the licensed product’s guidance says anticoagulant users should be monitored, and warfarin users need their INR (a clotting test) checked when starting or stopping [10]
• take other medicines that affect bleeding (such as aspirin or clopidogrel), or have a bleeding disorder or surgery planned. VITAL saw no excess bleeding at 1 g a day [2], but ask first
• have an irregular heartbeat or heart disease
• have a fish or shellfish allergy (check the label)
• are pregnant or breastfeeding. The licensed product says it shouldn’t be used in pregnancy unless clearly necessary [10]. Follow your national fish-intake advice, such as the NHS oily-fish limit [1] or the US lower-mercury advice [11].

Where to buy

Look for a label that states the EPA and DHA amounts per serving (not just “fish oil”), and third-party testing for purity. Algae oil is an option if you avoid fish. Our omega-3 buying guide explains how we choose products.

FAQ

Is omega 3 worth taking?

A major review of 86 trials found little or no difference to deaths or cardiovascular events in most people [3]. The clearest effect is on triglycerides, a type of blood fat, which fell by about 15% [3]. We rate the evidence C, and oily fish is a simpler place to start [1].

What is omega 3 good for?

The clearest effect is on triglycerides, which fell by about 15% in a major review [3]. For depression, an 18,353-adult trial found no lower risk [8], and for memory a 2024 review suggested a possible benefit for executive function [9]. Heart-health results for supplements have mostly been disappointing [2][3][4].

How much omega 3 per day?

The US has no set amount for EPA and DHA, and the FDA says labels shouldn’t recommend more than 2 g a day of EPA plus DHA [11]. The big trials used about 1 g of omega-3 a day [2][4]. These are amounts used in studies, not recommendations.

Who should not take omega 3?

Check with a doctor or pharmacist first if you take blood thinners such as warfarin, have a bleeding disorder or surgery planned, have an irregular heartbeat or heart disease, have a fish or shellfish allergy, or are pregnant or breastfeeding [7][10].

Can you take omega 3 with magnesium?

We found no verified data on omega-3 and magnesium taken together, so we can’t say whether the combination is safe or unsafe. Check with a doctor or pharmacist if you also take other medicines, especially blood thinners, which can interact with high-dose omega-3 [10].

Related pages

• Omega-3 vs fish oil
• Vitamin D: tested alongside omega-3 in the VITAL trial
• CoQ10: another supplement people take for heart health
• Our omega-3 buying guide
• Longevity supplements for beginners: where this fits in a beginner’s routine
• All supplements A-Z

Talk to your doctor

This page is for general information and is not medical advice. Speak to a doctor or pharmacist before starting any supplement, especially if you are pregnant or breastfeeding, take any medicine, or have a health condition.

References

We cite only studies and official pages we checked against PubMed, the publisher or the agency’s own site. The A to E evidence grades are explained in our editorial policy. See also our medical disclaimer and affiliate disclosure.

1. NHS. Fish and shellfish nutrition. nhs.uk (accessed 1 November 2026)
2. Manson JE, Cook NR, Lee IM, et al. Marine n-3 fatty acids and prevention of cardiovascular disease and cancer. N Engl J Med. 2019. PubMed · DOI
3. Abdelhamid AS, Brown TJ, Brainard JS, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2020. PubMed · DOI
4. ASCEND Study Collaborative Group, Bowman L, Mafham M, et al. Effects of n-3 fatty acid supplements in diabetes mellitus. N Engl J Med. 2018. PubMed · DOI
5. Nicholls SJ, Lincoff AM, Garcia M, et al. Effect of high-dose omega-3 fatty acids vs corn oil on major adverse cardiovascular events in patients at high cardiovascular risk: the STRENGTH randomized clinical trial. JAMA. 2020. PubMed · DOI
6. Bhatt DL, Steg PG, Miller M, et al. Cardiovascular risk reduction with icosapent ethyl for hypertriglyceridemia. N Engl J Med. 2019. PubMed · DOI
7. Gencer B, Djousse L, Al-Ramady OT, et al. Effect of long-term marine omega-3 fatty acids supplementation on the risk of atrial fibrillation in randomized controlled trials of cardiovascular outcomes: a systematic review and meta-analysis. Circulation. 2021. PubMed · DOI
8. Okereke OI, Vyas CM, Mischoulon D, et al. Effect of long-term supplementation with marine omega-3 fatty acids vs placebo on risk of depression or clinically relevant depressive symptoms and on change in mood scores: a randomized clinical trial. JAMA. 2021. PubMed · DOI
9. Suh SW, Lim E, Burm SY, et al. The influence of n-3 polyunsaturated fatty acids on cognitive function in individuals without dementia: a systematic review and dose-response meta-analysis. BMC Med. 2024. PubMed · DOI
10. Omacor 1000 mg soft capsules: summary of product characteristics (sections 4.4-4.6, 4.8). electronic Medicines Compendium. emc (accessed 1 November 2026)
11. National Institutes of Health, Office of Dietary Supplements. Omega-3 fatty acids: health professional fact sheet. ods.od.nih.gov (accessed 1 November 2026)