How to Read a Fish Oil Label: EPA and DHA Amounts, Forms, Oxidation and Purity
A plain guide to reading a fish oil label: EPA and DHA per serving, the form of the oil, freshness, purity and what independent lab studies have found, with links to detail pages.
Content last updated . This page has not been medically reviewed.
Quick answer
The big number on the front of a fish oil bottle is usually the weight of the oil, not the amount of omega-3. The figures that matter are the EPA and DHA lines on the Supplement Facts panel, the serving size, and any information on freshness and testing. This page is the starting point for reading a label. It gives no brand advice and no personal amounts. Each topic has its own page, linked below. For general label reading see Reading supplement labels and Comparing supplement labels and cost per serving.
How we label the evidence: mixed means studies disagree; insufficient evidence means too little to say; Proper evidence not found means we looked in the sources named and found nothing usable.
A label checklist
| What to check | Why it matters | Detail page |
|---|---|---|
| Serving size and capsules per serving | In the US, one serving is the maximum amount the label recommends per eating occasion, or one unit if there is no recommendation [1] | More about Serving size and capsules per serving → |
| EPA and DHA lines in milligrams | The US panel must list the names and quantities of dietary ingredients along with the serving size [1] | same page |
| Form of the oil (triglyceride, ethyl ester, phospholipid, free fatty acid) | Absorption studies differ by form, but clinical outcomes were not compared | More about Form of the oil (triglyceride, ethyl ester, phospholipid, free fatty acid) → |
| Freshness | Omega-3 oils oxidize, and independent studies found large differences between products | More about Freshness → |
| Purity and testing | Refining largely removes dioxins and PCBs [2], but products and markets differ | More about Purity and testing → |
| Storage directions | Authors of one stability study advise low temperature and protection from light [3] | More about Storage directions → |
| Burps and aftertaste | Common, usually mild side effects | More about Burps and aftertaste → |
Total oil is not EPA plus DHA
Trials report amounts of EPA and DHA, not amounts of oil. One four-week trial gave 1.3 g a day of EPA plus DHA (about 816 mg EPA and 522 mg DHA) as six capsules a day. [4] That is a study amount, not advice. On a product, look at the EPA and DHA lines, then at how many capsules make a serving, and do the multiplication yourself. A worked example is on the per-serving page.Do labels match what is inside?
Independent analyses differ by country and year, so no single answer fits every product. Some found most products matched their EPA and DHA claims. One US analysis of 46 products found EPA and DHA met the label declaration in more than 80%. [5] A study of 32 New Zealand products found only 3 contained as much EPA and DHA as labeled (an erratum was later published). [6] A later analysis of 47 products from the same market reported 91% complied, but several of its authors work for an omega-3 trade association. [7] A Chinese market study found EPA met the label claim in 64% of capsule products and DHA in 48%. [8] Evidence label: mixed. These studies are snapshots of particular markets, not a guide to any bottle you hold.Form of the oil
Oils are sold as ethyl esters, triglycerides, free fatty acids or phospholipids. A review found apparent absorption seemed lowest for the ethyl ester form and highest for the free fatty acid form, but called the studies too varied to draw firm conclusions. [9] In a matched-dose trial of 66 healthy adults, plasma EPA plus DHA after four weeks did not differ significantly between ethyl ester fish oil, triglyceride fish oil and krill oil. [4] Do not assume a "triglyceride form" label guarantees a better result for health. See the forms page.Freshness and purity
Omega-3 oils are highly prone to oxidation, and a 2013 review noted that human trials had not reported the oxidation state of the oil used. [10] In a Canadian analysis of 171 products, 50% exceeded voluntary recommended levels for oxidation markers. [11] Price and best-before date were poor markers of quality in a New Zealand study, and price was unrelated to quality in the Chinese study. [6][8] The FDA states that it does not approve dietary supplements for safety and effectiveness. [12] Third-party seals exist; what they check is explained on Quality testing and certifications.Other things on the label
- Vitamins A and D. Fish liver oils such as cod liver oil also contain vitamins A and D, in amounts that vary by product, and both can be harmful in excess. [13] See cod liver oil.
- Source. "Fish oil" implies fish. Algal oils are a vegetarian source of DHA. [13]
- Allergy. The US prescribing information for a prescription omega-3 product advises telling patients with fish or shellfish hypersensitivity about the potential for allergic reactions. [14] Check any allergen statement on supplements.
The "omega-3 index"
Some marketing offers an "omega-3 index" blood test. In the trial above, red blood cell EPA plus DHA was measured to compare products. [4] In the sources we read, we found nothing showing that a home test result should guide what a person takes: Proper evidence not found (searched: the sources listed on this page). Ask a clinician.Frequently asked questions
How do I find the real omega-3 in a fish oil capsule?
Read the EPA and DHA lines in milligrams on the Supplement Facts panel and the serving size. The weight of the oil is a different quantity. [1]
Is triglyceride-form fish oil better than ethyl ester?
Absorption studies point in different directions and the reviews call them hard to compare. No source we read compared the forms on heart or eye outcomes. [9][4]
Does a higher price mean better quality?
In the New Zealand and Chinese studies we read, price was not a reliable sign of quality. [6][8]
Are fish oil supplements approved by the FDA before sale?
The FDA states that it does not approve dietary supplements for safety and effectiveness. [12]
Who should check with a clinician first?
Anyone who takes medicines that affect bleeding, has a fish or shellfish allergy or a heart rhythm condition, is due for surgery, is pregnant, or is choosing a product for a child. The prescription labels cited above carry bleeding, allergy and heart-rhythm warnings. [14][15]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety reminder
US prescribing information for prescription omega-3 products warns about bleeding [14] and, for one product, a possible link with more frequent recurrences of atrial fibrillation in people who already have it. [15] Tell your surgical team and pharmacist about any supplement. See Omega-3 safety and interactions and Medication interactions.
References
- FDA, Dietary Supplement Labeling Guide: Chapter IV, Nutrition Labeling (US). Read 2026-10-22.
- Sun SX et al. Tracking pollutants in dietary fish oil: from ocean to table. Environ Pollut 2018. Read 2026-10-22.
- Yenipazar H, Sahin-Yesilcubuk N. Effect of packaging and encapsulation on the oxidative and sensory stability of omega-3 supplements. Food Sci Nutr 2023 (full text). Read 2026-10-22.
- Similar EPA and DHA plasma levels achieved with fish oil or krill oil in a randomized double-blind four-week bioavailability study. Lipids Health Dis 2015. Read 2026-10-22.
- Srigley CT, Rader JI. Content and composition of fatty acids in marine oil omega-3 supplements. J Agric Food Chem 2014. Read 2026-10-22.
- Albert BB et al. Fish oil supplements in New Zealand are highly oxidised and do not meet label content of n-3 PUFA. Sci Rep 2015 (an erratum was published in 2016). Read 2026-10-22.
- Bannenberg G et al. Omega-3 long-chain polyunsaturated fatty acid content and oxidation state of fish oil supplements in New Zealand. Sci Rep 2017 (authors include staff of an omega-3 trade association). Read 2026-10-22.
- Zhou Q et al. Systematically investigating the qualities of commercial encapsulated and industrial-grade bulk fish oils in the Chinese market. Foods 2025. Read 2026-10-22.
- Ghasemifard S, Turchini GM, Sinclair AJ. Omega-3 long chain fatty acid "bioavailability": a review of evidence and methodological considerations. Prog Lipid Res 2014. Read 2026-10-22.
- Albert BB et al. Oxidation of marine omega-3 supplements and human health. Biomed Res Int 2013. Read 2026-10-22.
- Jackowski SA et al. Oxidation levels of North American over-the-counter n-3 supplements and the influence of supplement formulation and delivery form on evaluating oxidative safety. J Nutr Sci 2015. Read 2026-10-22.
- FDA, Dietary Supplement Products and Ingredients. Read 2026-10-22.
- NCCIH, Omega-3 Supplements: What You Need To Know. Read 2026-10-22.
- FDA-approved prescribing information, icosapent ethyl prescription capsules, DailyMed, revised 3/2026. Read 2026-10-22.
- FDA-approved prescribing information, omega-3-acid ethyl esters prescription capsules, DailyMed, revised 11/2024. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.