Fish oil, krill oil, or algae oil?

All deliver EPA/DHA. Fish oil is the most studied and usually cheapest per gram. Krill oil is in phospholipid form (marketed as better absorbed) but lower-dose and pricier. Algae oil is the vegan option. Match the EPA/DHA total, not the marketing.

How much EPA versus DHA do I need?

For triglycerides and general health, the combined EPA+DHA total matters most. Higher-EPA formulas are often used for mood and inflammation, higher-DHA for pregnancy and the brain, but the distinction is modest for most people.

Does it thin the blood?

At higher doses omega-3 can mildly reduce clotting. It's usually fine, but tell your provider if you take anticoagulants or have surgery scheduled.

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Omega-3 (Fish Oil)

Omega & fatty acid · Also known as: EPA, DHA, fish oil, marine omega-3

Evidence reviewed by Troy Hounshell, PT, ScD · Last reviewed September 8, 2026

Marine fatty acids (EPA and DHA) that support heart, brain, joint, and eye health.

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What it is

Omega-3s are essential fats your body can't make efficiently on its own. The two most active forms, EPA and DHA, come mainly from fatty fish and fish oil; algae oil is a plant-based source. They are building blocks of cell membranes and help regulate inflammation.

How it works

EPA and DHA are long-chain omega-3 fats that get built into your cell membranes, keeping them fluid and shaping how cells signal. Your body also turns them into compounds (like resolvins) that help switch off inflammation once it has done its job. In the bloodstream they lower triglycerides by reducing how much fat the liver packages and releases. DHA in particular is a major structural fat in the brain and the retina.

What it's been studied for

Taken to support heart health and triglycerides, brain and cognition, joint comfort, dry-eye relief, and healthy pregnancy.

What the evidence shows

Omega-3s reliably lower triglycerides in a dose-dependent way, and improve markers of inflammation. In pregnancy, they reduce the risk of early preterm birth. The evidence is more mixed elsewhere: large trials have not shown clear reductions in heart attacks or strokes, cognitive benefits appear mainly at higher doses in early decline, and dry-eye results conflict. In short, strong for blood fats and inflammation, modest or mixed for hard outcomes.

Who should consider it

People who rarely eat oily fish are the clearest candidates, since EPA and DHA come mainly from seafood. Others who often consider it: people with high triglycerides, those focused on heart or joint comfort, pregnant people (for DHA and fetal development), and vegetarians or vegans (who can use algae oil). The body converts plant omega-3 (ALA, from flax and walnuts) into EPA/DHA very inefficiently, so a fish or algae source matters if you don't eat fish.

Amounts commonly studied

Studies often use 1-4 g of combined EPA+DHA per day; triglyceride effects are dose-dependent. Check the EPA/DHA numbers, not just the fish-oil weight.

How to take it

Doses are usually 1-3 g of combined EPA+DHA per day, taken with a meal containing fat for better absorption. Read the label for the actual EPA and DHA numbers — a '1,000 mg fish oil' softgel may contain only around 300 mg of EPA+DHA. Taking it with food, choosing an enteric-coated or triglyceride-form product, or freezing softgels can cut down on fishy burps. Store it cool and mind the freshness, since fish oil oxidizes.

Forms & absorption

Triglyceride and re-esterified triglyceride forms tend to absorb better than ethyl esters. Algae oil is a vegan option. Freshness matters, since fish oil can go rancid.

Food sources

Best sources are oily fish: salmon, sardines, mackerel, herring, and anchovies. Algae is the vegan source of EPA/DHA. Flaxseed, chia, and walnuts provide ALA, which converts to EPA/DHA inefficiently.

Safety & interactions

Generally safe; may cause fishy burps or mild stomach upset. At higher doses it can mildly thin the blood, so coordinate with your provider if you take anticoagulants or are heading into surgery.

Myths & what it won't do

Myth: fish oil prevents heart attacks. Reality: it reliably lowers triglycerides, but large trials found little or no effect on preventing heart attacks or strokes in most people — the clearest benefit is for blood fats and inflammation, not hard cardiac outcomes. Myth: plant omega-3 from flax or chia is an equal substitute. Reality: the body converts it to EPA/DHA poorly, so it isn't a reliable replacement for fish or algae oil.

Common questions

Fish oil, krill oil, or algae oil?: All deliver EPA/DHA. Fish oil is the most studied and usually cheapest per gram. Krill oil is in phospholipid form (marketed as better absorbed) but lower-dose and pricier. Algae oil is the vegan option. Match the EPA/DHA total, not the marketing.
How much EPA versus DHA do I need?: For triglycerides and general health, the combined EPA+DHA total matters most. Higher-EPA formulas are often used for mood and inflammation, higher-DHA for pregnancy and the brain, but the distinction is modest for most people.
Does it thin the blood?: At higher doses omega-3 can mildly reduce clotting. It's usually fine, but tell your provider if you take anticoagulants or have surgery scheduled.

The amounts listed here are what published research has used — not a prescription or a recommended dose for you. Confirm anything you plan to take with your own healthcare provider, especially if you take medications, are pregnant or nursing, or have a health condition.

Research on Omega-3 (Fish Oil)

Recommendations on this page are informed by published research. This is educational information, not medical advice.

Wang T, Zhang X, Zhou N, et al. Association Between Omega-3 Fatty Acid Intake and Dyslipidemia: A Continuous Dose-Response Meta-Analysis of Randomized Controlled Trials. J Am Heart Assoc. 2023;12(11):e029512. View study →
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;(3):CD003177. View study →Note: Omega-3s reliably lower triglycerides, but this large review found little or no effect on preventing heart attacks or strokes — the clearest benefit is for blood fats, not cardiovascular events.
Kavyani Z, Musazadeh V, Fathi S, et al. Efficacy of the omega-3 fatty acids supplementation on inflammatory biomarkers: An umbrella meta-analysis. Int Immunopharmacol. 2022;111:109104. View study →
Shahinfar H, Yazdian Z, Avini NA, et al. A systematic review and dose-response meta-analysis of omega-3 supplementation on cognitive function. Sci Rep. 2025;15(1):30610. View study →Note: The evidence is mixed — benefits appear mainly at higher doses and in early or mild cognitive decline, with little effect in advanced disease.
Giannaccare G, Pellegrini M, Sebastiani S, et al. Efficacy of Omega-3 Fatty Acid Supplementation for Treatment of Dry Eye Disease: A Meta-Analysis of Randomized Clinical Trials. Cornea. 2019;38(5):565-573. View study →Note: Evidence is mixed — this analysis found a benefit, but a large 2018 trial (DREAM) found omega-3 no better than placebo for dry eye.
Middleton P, Gomersall JC, Gould JF, et al. Omega-3 fatty acid addition during pregnancy. Cochrane Database Syst Rev. 2018;(11):CD003402. View study →

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