The short answer
Most adults don't need a supplement if they eat oily fish regularly:
- Australian guidelines suggest aiming for about 610 mg (men) or 430 mg (women) of long-chain omega-3s (EPA and DHA) a day;
- two fish meals a week, preferably oily fish, provides roughly that amount;
- if you use a supplement, go by the EPA and DHA on the label, not the total fish oil;
- don't go above 3,000 mg a day, and check with your practitioner first if you take blood thinners, are pregnant or have a heart rhythm problem.
Fish oil is one of the most popular supplements in Australia, but there's a lot of confusion about how much to take and what it actually does. As a dietitian, here's what I tell clients, based on Australian guidelines and the best research.
What are omega-3s and why do you need them?
Fish oil contains the long-chain omega-3 fats EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Your body can't make enough of them on its own, so they need to come from food.6 DHA is an important building block of the brain, nerves and the retina in your eyes, and both play a role in heart health and inflammation.6
Plant foods such as linseed (flaxseed), chia seeds, walnuts and canola oil contain a different omega-3 called ALA. Your body can convert some ALA to EPA and DHA, but only in small amounts.6
How much fish oil should you take a day?
Australian guidelines give two levels for long-chain omega-3s (EPA, DHA and DPA combined):6,7
- Adequate intake (enough to avoid deficiency): 160 mg a day for men and 90 mg a day for women.
- Suggested dietary target (to help reduce chronic disease risk): 610 mg a day for men and 430 mg a day for women.
- Pregnancy and breastfeeding: an adequate intake of 115 mg a day in pregnancy and 145 mg a day while breastfeeding.
- Upper level: no more than 3,000 mg a day for children, teenagers and adults.
Two fish meals a week, preferably oily fish such as salmon, sardines, mackerel or tuna, provides about 430–570 mg a day on average.7 If you don't eat fish, a supplement can help you reach the target. Check the label for the amount of EPA and DHA, as a capsule's total fish oil content is much higher than its omega-3 content.
Get advice on supplements
Find nutritionists and naturopaths on HealthBank who can advise on fish oil and other supplements. Many offer a free discovery call, online, by phone or in person.
Find a nutritionist or naturopath →Is fish oil good for you? What the evidence shows
- Triglycerides: long-chain omega-3s lower blood triglycerides by about 15%, with bigger doses having a bigger effect.1
- Heart disease: a Cochrane review of 86 trials found that more long-chain omega-3 may slightly reduce coronary heart disease events and deaths, but makes little or no difference to overall deaths, strokes or cardiovascular events.1
- Pregnancy: omega-3 supplements in pregnancy reduce the risk of preterm birth.4 Talk to your practitioner before starting any supplement in pregnancy.
- Depression: there isn't enough high-quality evidence to know whether omega-3s help treat depression.5
Omega-3s have been studied in many other conditions, but the evidence varies a lot. Fish oil isn't a treatment for any medical condition, so don't use it instead of your usual care.
Who should be careful with fish oil?
- People with a heart rhythm problem, or at risk of one. In large heart trials, omega-3 supplements were linked with a higher risk of atrial fibrillation (an irregular heartbeat), especially at doses above 1 g a day.3
- People taking blood-thinning medicines, or with surgery coming up. A meta-analysis found omega-3s didn't increase bleeding overall, though high-dose purified EPA caused a small increase.2 Always tell your doctor you take fish oil.
- Anyone considering high doses. The upper level is 3,000 mg a day, partly because very high intakes may affect immune response and bleeding time.6
- People with a seafood allergy. Some people allergic to fish may react to fish oil supplements, so check with your doctor first.
- People with a mental health condition or taking regular medicines. Check with your practitioner before starting.
Does fish oil quality matter?
Yes. Quality varies between products. In Australia, choose a supplement that's listed with the Therapeutic Goods Administration (look for an AUST L number on the label), check how much EPA and DHA it provides per capsule, and store it as directed. If you're unsure which product or dose suits you, ask your practitioner or pharmacist.
Food first
Two fish meals a week gets most people close to the omega-3 target, plus protein, iodine and other nutrients a capsule doesn't provide.
Not sure if you need a supplement?
A HealthBank nutritionist or naturopath can look at what you eat, work out whether you need fish oil and help you choose a safe dose.
Find a nutritionist or naturopath →Frequently asked questions
How much fish oil should I take a day?
Australian guidelines suggest about 610 mg (men) or 430 mg (women) of EPA and DHA a day from food or supplements. Go by the EPA and DHA on the label, not the total fish oil.
Is it better to eat fish or take fish oil?
Food first. Two fish meals a week, preferably oily fish, provides roughly the recommended amount along with other nutrients.
Is fish oil good for your heart?
Omega-3s lower triglycerides and may slightly reduce coronary heart disease events, but they make little difference to overall heart attacks, strokes or deaths.
Can you take too much fish oil?
Yes. The Australian upper level is 3,000 mg of long-chain omega-3 a day, and doses above 1 g a day are linked with a higher risk of atrial fibrillation.
Is fish oil safe with blood thinners?
Studies haven't found an overall increase in bleeding, but always tell your doctor you take fish oil, especially before surgery.
Can I get omega-3s from plant foods?
Linseed, chia, walnuts and canola oil contain ALA, but your body converts only a small amount into EPA and DHA.
References
Research (PubMed)
- 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. PubMed 32114706
- Javaid M, Kadhim K, Bawamia B, Cartlidge T, Farag M, Alkhalil M. Bleeding risk in patients receiving omega-3 polyunsaturated fatty acids: a systematic review and meta-analysis of randomized clinical trials. J Am Heart Assoc. 2024;13(10):e032390. PubMed 38742535
- Gencer B, Djousse L, Al-Ramady OT, Cook NR, Manson JE, Albert CM. 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;144(25):1981–1990. PubMed 34612056
- Middleton P, Gomersall JC, Gould JF, Shepherd E, Olsen SF, Makrides M. Omega-3 fatty acid addition during pregnancy. Cochrane Database Syst Rev. 2018;11:CD003402. PubMed 30480773
- Appleton KM, Voyias PD, Sallis HM, et al. Omega-3 fatty acids for depression in adults. Cochrane Database Syst Rev. 2021;11:CD004692. PubMed 34817851
Australian guidelines
- National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand: Fats – total fat and fatty acids. View source
- National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand: Macronutrient balance (chronic disease). View source
This article is general information and isn't a substitute for personalised advice. Speak to your practitioner about your situation.
Robbie is a Sydney-based Accredited Practising Dietitian (APD) and Exercise Scientist with over 17 years of experience. He holds a Bachelor of Exercise Science (Nutrition) and a Master of Nutrition and Dietetics, and is the Director and Co-founder of HealthBank.