Also known as Fish Oil, Krill Oil, EPA, DHA
Long-chain polyunsaturated fatty acids from fish or algal oil that are incorporated into cell membranes and reduce pro-inflammatory eicosanoid production; linked to cardiovascular, joint, and neurological benefits.
Reported side effects:Unpleasant tasteBad breathHeartburn
Be careful if: pregnant, breastfeeding, some medical situations
Ask first if you take: blood thinners (anticoagulants or antiplatelets)
Upper limit: 5 grams per day EPA plus DHA (supplemental) — EFSA assessed long-term intake up to about 5 g a day of EPA and DHA supplements without identified harmful effects, and FDA likewise concluded up to 5 g a day from dietary supplements is acceptable as recommended (both as cited by NIH ODS)
Suspect a side effect? Report it to the MHRA Yellow Card scheme ↗
We link to relevant studies and leave interpretation to you and your healthcare professional.
The large figures are what the studies reported for each thing they measured. Open a card for every result.
Colour keyReported a benefitNo clear benefitUnclearPossible harmAmber is for highlights, such as where the most research is. It never means a result was good.
No figure given: Impulsive actions (no clear benefit); Impulsive thinking (reported a benefit); Not planning ahead (reported a benefit); Overall impulsiveness (reported a benefit).
Every resultNo figure given: Depression symptoms (mixed results).
Also measured alongside: Quality of life (no clear benefit).
Every resultAlso measured alongside: Anti-inflammatory painkiller use (reported a benefit).
1 more measureWhat sources report about side effects, who should be careful, and medicines to ask about first.
| Reported effect | How often | Basis | Sources |
|---|---|---|---|
| Atrial fibrillation — two large trials found 4 grams a day of omega-3 for several years slightly increased the risk in people with cardiovascular disease or a high risk of it | unknown | Listed by NIH ODS fact sheets | Omega-3 Fatty Acids (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-09) |
| Applies to | What sources say | Sources |
|---|---|---|
| pregnant | No caution against use in pregnancy in the sources checked: ACOG and FDA advise pregnant women to consume 8 to 12 ounces a week of seafood lower in mercury, and EFSA advises an additional 100 to 200 mg a day of DHA in pregnancy (as cited by NIH ODS). | Omega-3 Fatty Acids (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-09) |
| breastfeeding | No breastfeeding-specific caution found in the sources checked (NIH ODS omega-3 fact sheet); pregnant and breastfeeding women are advised to keep to low-mercury seafood choices. | Omega-3 Fatty Acids (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-09) |
| some medical situations | People taking warfarin or similar anticoagulants should discuss omega-3 supplement use with their clinician (NIH ODS). | Omega-3 Fatty Acids (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-09) |
| Severity | Medicine | Sources |
|---|---|---|
| caution | blood thinners (anticoagulants or antiplatelets) — Fish oil can have antiplatelet effects at high doses and might prolong clotting times (raised INR) when taken with warfarin; most research at 3 to 6 grams a day shows no significant effect on anticoagulant status, and reviews have not found clinically significant bleeding (NIH ODS). | Omega-3 Fatty Acids (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-09) |
5 grams per day EPA plus DHA (supplemental) — EFSA assessed long-term intake up to about 5 g a day of EPA and DHA supplements without identified harmful effects, and FDA likewise concluded up to 5 g a day from dietary supplements is acceptable as recommended (both as cited by NIH ODS)
Audited published research for Omega-3 (EPA/DHA) by condition. Drill into a pair page for the full breakdown.
What this means: Bars count reported findings, not treatment effectiveness or certainty.
One study may report several findings or appear in more than one pairing. Counts do not show the size of an effect. Comparable numerical estimates are not established for this summary.
| Compound and condition | Findings (count) | Studies (count) | Reported results (finding counts) | How sure? |
|---|---|---|---|---|
| ADHD | 7 | 3 | Benefit: 5; no benefit: 2; harm: 0; unclear: 0; not recorded / unrecognised: 0 | Not formally graded |
| Depression | 13 | 2 | Benefit: 3; no benefit: 10; harm: 0; unclear: 0; not recorded / unrecognised: 0 | Not formally graded |
| Inflammation | 3 | 1 | Benefit: 3; no benefit: 0; harm: 0; unclear: 0; not recorded / unrecognised: 0 | Not formally graded |
| Joint Pain | 5 | 1 | Benefit: 1; no benefit: 4; harm: 0; unclear: 0; not recorded / unrecognised: 0 | Not formally graded |
Where people report using it and what trials suggest
Common claims the trials do not support
EPA/DHA from fish or algae. Strong for severe hypertriglyceridaemia (high-dose EPA), otherwise cardiovascular results in large trials are inconsistent.
Evidence grades reflect study quality and consistency, not marketing claims.
Ordered by strength of evidence, then result direction.
01Role of the EPA: DHA dosing ratio in omega-3 supplements on blood fatty acid profiles and inflammation: a systematic review and meta-analysisKhabir Z, et al. · Critical reviews in food science and nutrition · 2026PMID 41568426 ↗02Comparative Effectiveness of Nutritional Supplements in the Treatment of Knee Osteoarthritis: A Network Meta-AnalysisZhang Y, et al. · Nutrients · 2025PMID 40806131 ↗03A systematic review and dose response meta analysis of Omega 3 supplementation on cognitive functionShahinfar H, et al. · Scientific reports · 2025PMID 40836005 ↗04The effect of two anti-inflammatory dietary components, omega-3 and resveratrol, on endometriosisSienko A, et al. · Ginekologia polska · 2024PMID 37768015 ↗05A Systemic Review on Nutraceutical Supplements used in the Management of OsteoarthritisNooreen Z, et al. · Recent advances in food, nutrition & agriculture · 2024PMID 38258782 ↗06Nutraceuticals in Psychiatric Disorders: A Systematic ReviewBozzatello P, et al. · International journal of molecular sciences · 2024PMID 38732043 ↗Reported results grouped by condition. Values and units are preserved as recorded; missing information is not estimated.
How to read this table
Reported direction, numerical results and study design are separate. Certainty has not been formally graded in this table.
| What was measured | Reported findings | Result and units | Reported sample and duration | Study / source |
|---|---|---|---|---|
| ADHD core symptoms (overall) | Omega-3 polyunsaturated fatty acids did not significantly improve ADHD core symptoms (overall) (SMD: -0.16; 95% CI, -0.34 to 0.01; P = .07) compared with placebo in 1,789. (95% CI, -0.34 to 0.01; P = .07)No clear benefit | SMD: -0.16 Recorded unit: Not reported | Sample (as reported): 1,789 Follow-up: Not reported | Meta-analysis · 2023 Study detailsOmega-3 Polyunsaturated Fatty Acids for Core Symptoms of Attention-Deficit/Hyperactivity Disorder: A Meta-Analysis of Randomized Controlled Trials. Meta-Analysis |
| ADHD core symptoms (treatment duration ≥ 4 months) | Omega-3 polyunsaturated fatty acids improved ADHD core symptoms (treatment duration ≥ 4 months) (SMD: -0.35; 95% CI,-0.61 to -0.09; P = .007) compared with placebo (at least 4 months). (95% CI,-0.61 to -0.09; P = .007)Benefit seen | SMD: -0.35 Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: at least 4 months | Meta-analysis · 2023 Study detailsOmega-3 Polyunsaturated Fatty Acids for Core Symptoms of Attention-Deficit/Hyperactivity Disorder: A Meta-Analysis of Randomized Controlled Trials. Meta-Analysis |
| ADHD severity (standardized mean difference in rating scales) | Omega-3 fatty acid supplementation improved ADHD severity (standardized mean difference in rating scales) compared with placebo in 699.Benefit seen | Not reported Recorded unit: Not reported | Sample (as reported): 699 Follow-up: Not reported | Meta-analysis · 2011 Study detailsOmega-3 fatty acid supplementation for the treatment of children with attention-deficit/hyperactivity disorder symptomatology: systematic review and meta-analysis. Meta-Analysis |
| Total BIS-11c score | Mediterranean diet and/or omega-3 fatty acids improved Total BIS-11c score from baseline (before-after within one group) (P = .049) in 60 (8 weeks). (P = .049)Benefit seen | Not reported Recorded unit: Not reported | Sample (as reported): 60 Follow-up: 8 weeks | Randomised trial · 2022 Study detailsImpulsiveness in children with attention-deficit/hyperactivity disorder after an 8-week intervention with the Mediterranean diet and/or omega-3 fatty acids: a randomised clinical trial. Randomized Controlled Trial |
| Total cognitive score | Mediterranean diet and/or omega-3 fatty acids improved Total cognitive score from baseline (before-after within one group) in 60 (8 weeks).Benefit seen | Not reported Recorded unit: Not reported | Sample (as reported): 60 Follow-up: 8 weeks | Randomised trial · 2022 Study detailsImpulsiveness in children with attention-deficit/hyperactivity disorder after an 8-week intervention with the Mediterranean diet and/or omega-3 fatty acids: a randomised clinical trial. Randomized Controlled Trial |
| Total motor score | Mediterranean diet and/or omega-3 fatty acids did not significantly improve Total motor score from baseline (before-after within one group) in 60 (8 weeks).No clear benefit | Not reported Recorded unit: Not reported | Sample (as reported): 60 Follow-up: 8 weeks | Randomised trial · 2022 Study detailsImpulsiveness in children with attention-deficit/hyperactivity disorder after an 8-week intervention with the Mediterranean diet and/or omega-3 fatty acids: a randomised clinical trial. Randomized Controlled Trial |
| Total nonplanning scores | Mediterranean diet and/or omega-3 fatty acids improved Total nonplanning scores from baseline (before-after within one group) in 60 (8 weeks).Benefit seen | Not reported Recorded unit: Not reported | Sample (as reported): 60 Follow-up: 8 weeks | Randomised trial · 2022 Study detailsImpulsiveness in children with attention-deficit/hyperactivity disorder after an 8-week intervention with the Mediterranean diet and/or omega-3 fatty acids: a randomised clinical trial. Randomized Controlled Trial |
| What was measured | Reported findings | Result and units | Reported sample and duration | Study / source |
|---|---|---|---|---|
| depression symptoms | Depression symptoms improved with an SMD of -0.28 vs placebo in 2160 participants. (P=0.004)Benefit seen | -0.28 SMD Recorded unit: Not reported | Sample (as reported): 2160 Follow-up: Not reported | Meta-analysis · 2019 Study detailsEfficacy of omega-3 PUFAs in depression: A meta-analysis. Meta-Analysis |
| depression symptoms (DHA-pure and DHA-major) | No benefit was found for DHA-pure and DHA-major formulations compared to placebo.No clear benefit | Not reported Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: Not reported | Meta-analysis · 2019 Study detailsEfficacy of omega-3 PUFAs in depression: A meta-analysis. Meta-Analysis |
| depression symptoms (EPA-major) | Depression symptoms improved with an SMD of -1.03 vs placebo for EPA-major formulations. (P=0.03)Benefit seen | -1.03 SMD Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: Not reported | Meta-analysis · 2019 Study detailsEfficacy of omega-3 PUFAs in depression: A meta-analysis. Meta-Analysis |
| depression symptoms (EPA-pure) | Depression symptoms improved with an SMD of -0.50 vs placebo for EPA-pure formulations. (P=0.003)Benefit seen | -0.50 SMD Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: Not reported | Meta-analysis · 2019 Study detailsEfficacy of omega-3 PUFAs in depression: A meta-analysis. Meta-Analysis |
| adverse events | No difference in adverse events vs placebo (OR 1.27) in 1503 participants. (95% CI 0.99 to 1.64)No clear benefit | 1.27 OR Recorded unit: Not reported | Sample (as reported): 1503 Follow-up: Not reported | Systematic review · 2021 Study detailsOmega-3 fatty acids for depression in adults. Systematic Review |
| depressive symptomology (continuous) | Small benefit of 0.40 SMD vs placebo in 1848 people, but unlikely clinically meaningful. (95% CI -0.64 to -0.16)No clear benefit | -0.40 SMD Recorded unit: Not reported | Sample (as reported): 1848 Follow-up: Not reported | Systematic review · 2021 Study detailsOmega-3 fatty acids for depression in adults. Systematic Review |
| depressive symptomology (vs antidepressants) | No difference in depressive symptomology vs antidepressants (MD -0.70) in 40 participants. (95% CI -5.88 to 4.48)No clear benefit | -0.70 MD Recorded unit: Not reported | Sample (as reported): 40 Follow-up: Not reported | Systematic review · 2021 Study detailsOmega-3 fatty acids for depression in adults. Systematic Review |
| quality of life | No difference in quality of life vs placebo (SMD -0.38) in 476 participants. (95% CI -0.82 to 0.06)No clear benefit | -0.38 SMD Recorded unit: Not reported | Sample (as reported): 476 Follow-up: Not reported | Systematic review · 2021 Study detailsOmega-3 fatty acids for depression in adults. Systematic Review |
| remission rates | No difference in remission rates vs placebo (OR 1.13) in 609 participants. (95% CI 0.74 to 1.72)No clear benefit | 1.13 OR Recorded unit: Not reported | Sample (as reported): 609 Follow-up: Not reported | Systematic review · 2021 Study detailsOmega-3 fatty acids for depression in adults. Systematic Review |
| response rates | No difference in response rates vs placebo (OR 1.20) in 794 participants. (95% CI 0.80 to 1.79)No clear benefit | 1.20 OR Recorded unit: Not reported | Sample (as reported): 794 Follow-up: Not reported | Systematic review · 2021 Study detailsOmega-3 fatty acids for depression in adults. Systematic Review |
| response rates (vs antidepressants) | No difference in response rates vs antidepressants (OR 1.23) in 40 participants. (95% CI 0.35 to 4.31)No clear benefit | 1.23 OR Recorded unit: Not reported | Sample (as reported): 40 Follow-up: Not reported | Systematic review · 2021 Study detailsOmega-3 fatty acids for depression in adults. Systematic Review |
| trial non-completion | No difference in trial non-completion vs placebo (OR 0.92) in 1777 participants. (95% CI 0.70 to 1.22)No clear benefit | 0.92 OR Recorded unit: Not reported | Sample (as reported): 1777 Follow-up: Not reported | Systematic review · 2021 Study detailsOmega-3 fatty acids for depression in adults. Systematic Review |
| trial non-completion (vs antidepressants) | No difference in trial non-completion vs antidepressants (OR 1.00) in 40 participants. (95% CI 0.21 to 4.71)No clear benefit | 1.00 OR Recorded unit: Not reported | Sample (as reported): 40 Follow-up: Not reported | Systematic review · 2021 Study detailsOmega-3 fatty acids for depression in adults. Systematic Review |
| What was measured | Reported findings | Result and units | Reported sample and duration | Study / source |
|---|---|---|---|---|
| interleukin 6 (IL-6) | Omega-3 supplementation reduced IL-6 levels by an effect size of -0.22 compared to control in adults. (95% CI: -0.39, -0.05, p=0.010)Benefit seen | -0.22 Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: Not reported | Meta-analysis · 2022 Study detailsEfficacy of the omega-3 fatty acids supplementation on inflammatory biomarkers: An umbrella meta-analysis. Meta-Analysis |
| serum C-reactive protein (CRP) | Omega-3 supplementation reduced CRP levels by an effect size of -0.40 compared to control in adults. (95% CI: -0.56, -0.24, p<0.001)Benefit seen | -0.40 Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: Not reported | Meta-analysis · 2022 Study detailsEfficacy of the omega-3 fatty acids supplementation on inflammatory biomarkers: An umbrella meta-analysis. Meta-Analysis |
| Tumour necrosis factor α (TNFα) | Omega-3 supplementation reduced TNFα levels by an effect size of -0.23 compared to control in adults. (95% CI: -0.37, -0.08, p=0.002)Benefit seen | -0.23 Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: Not reported | Meta-analysis · 2022 Study detailsEfficacy of the omega-3 fatty acids supplementation on inflammatory biomarkers: An umbrella meta-analysis. Meta-Analysis |
| What was measured | Reported findings | Result and units | Reported sample and duration | Study / source |
|---|---|---|---|---|
| Morning stiffness | Omega-3 did not significantly improve morning stiffness compared to placebo. (95% CI-0.955-0.212, p = 0.221)No clear benefit | -0.224 standardized mean difference Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: 3 months | Meta-analysis · 2012 Study detailsOmega-3 polyunsaturated fatty acids and the treatment of rheumatoid arthritis: a meta-analysis. Meta-Analysis |
| NSAID consumption | Omega-3 reduced anti-inflammatory drug use compared to placebo, with a standardized mean difference of -0.518. (95% CI -0.915 to -0.121, p = 0.011)Benefit seen | -0.518 standardized mean difference Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: 3 months | Meta-analysis · 2012 Study detailsOmega-3 polyunsaturated fatty acids and the treatment of rheumatoid arthritis: a meta-analysis. Meta-Analysis |
| Physical function | Omega-3 did not significantly improve physical function compared to placebo. (95% CI-0.232-0.724, p = 0.314)No clear benefit | 0.264 standardized mean difference Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: 3 months | Meta-analysis · 2012 Study detailsOmega-3 polyunsaturated fatty acids and the treatment of rheumatoid arthritis: a meta-analysis. Meta-Analysis |
| Swollen joint count | Omega-3 did not significantly reduce swollen joint count compared to placebo. (95% CI-0.454-0.114, p = 0.241)No clear benefit | -0.170 standardized mean difference Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: 3 months | Meta-analysis · 2012 Study detailsOmega-3 polyunsaturated fatty acids and the treatment of rheumatoid arthritis: a meta-analysis. Meta-Analysis |
| Tender joint count | Omega-3 did not significantly reduce tender joint count compared to placebo. (95% CI-0.489-0.062, p = 0.128)No clear benefit | -0.214 standardized mean difference Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: 3 months | Meta-analysis · 2012 Study detailsOmega-3 polyunsaturated fatty acids and the treatment of rheumatoid arthritis: a meta-analysis. Meta-Analysis |
Associated conditions and community-reported outcomes, wrapped together on one page. Aggregates appear only once enough reports arrive.
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