Omega-3 Supplements: EPA, DHA, and Labels

VitaEvidence Editorial Team
Last reviewed: August 22, 2026
For general education, not personal medical advice. Read our Editorial Policy.

Omega-3 fatty acids come from foods like fish and seafood, as well as plant foods such as flaxseed and walnuts. Supplements include fish oil, krill oil, cod liver oil, and algal (algae) oil. The most useful way to compare products is to look beyond the front label and identify which omega-3s they provide—and in what amounts.

Quick answer: EPA and DHA are the marine omega-3s most people look for in a supplement. Check the Nutrition/Supplement Facts panel for the exact milligrams (mg) of EPA and DHA per serving, not just the total oil amount. Consider how much fish you already eat, whether you prefer a vegetarian source (algal oil), and any safety issues, especially if you use anticoagulants.

This article is general educational information, not medical advice.

What are ALA, EPA, and DHA—and why it matters

The three main omega-3 fatty acids are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is found mostly in plant oils and foods such as flaxseed, chia seeds, walnuts, and some vegetable oils. EPA and DHA are found mostly in fish and other seafood. The body converts only small amounts of ALA into EPA and DHA, so the source you choose matters when comparing products or planning your diet.

For general dietary intake, the National Academies set Adequate Intakes (AIs) for ALA: for adults, 1.6 grams/day for men and 1.1 grams/day for women. These values describe typical total intake goals for ALA and are not specific supplement dosing instructions. Most people can meet ALA needs through foods.

Food first: fish and seafood vs. supplements

Fatty fish such as salmon, sardines, herring, mackerel, and trout provide EPA and DHA. Algal oil is a vegetarian source of DHA and sometimes EPA. Supplements can be useful in some situations, but they do not automatically provide the same overall benefits as a food pattern that includes seafood and other nutritious foods.

The U.S. FDA advises choosing fish and shellfish lower in mercury and, for most adults, eating 2 to 3 servings per week from the “Best Choices” list. People who are pregnant or breastfeeding and young children are also encouraged to eat fish, selecting options lower in mercury and following age-appropriate serving sizes. If you already eat fish regularly, you may be getting EPA and DHA from food; if you rarely or never eat fish, a supplement or algal oil may be worth discussing with a clinician.

How to read an omega-3 supplement label

Don’t assume that a capsule labeled “1,000 mg fish oil” provides 1,000 mg of omega-3s. The active omega-3s of interest are EPA and DHA.

Check serving size: how many softgels or teaspoons make one serving.
Find the exact mg of EPA and the mg of DHA per serving. Add them if you want the combined EPA+DHA amount. This number is often far lower than the total oil amount.
Identify the source: fish oil, krill oil, cod liver oil, or algal oil. Cod liver oil also naturally contains vitamins A and D; verify the amounts on the label.
Look at other ingredients and storage instructions, and note the expiration date.
Consider quality cues: The NIH Office of Dietary Supplements advises that dietary supplements are not reviewed by the FDA for safety and effectiveness before they are sold. Choosing products from companies that share contact information and, when available, carry independent quality seals (for example, USP or NSF) can help you compare options.

Choosing among fish oil, cod liver oil, krill oil, and algal oil

Fish oil: Typically provides both EPA and DHA. The exact amounts vary by product, so rely on the label.
Cod liver oil: A source of EPA and DHA that also contains vitamins A and D. If you use it, account for those vitamins from all sources to avoid excessive intake.
Krill oil: Another marine source of EPA and DHA. Compare the listed EPA and DHA amounts directly to other options.
Algal oil: A vegetarian source that reliably provides DHA and, in some products, EPA. Check the label to see which omega-3s and how many mg per serving.

There is no single “best” form for everyone. Your choice can reflect your dietary pattern (for example, vegetarian vs. seafood eater), how much EPA and DHA you want per serving, and your tolerance for cost and capsule size.

Common mistakes to avoid

Equating total oil with omega-3s: Total “fish oil” mg is not the same as EPA+DHA mg.
Skipping the serving size: Some labels list omega-3s per two or three capsules, not one.
Relying on ALA for marine omega-3s: Because conversion of ALA to EPA and DHA is limited, plant-only omega-3s are not interchangeable with fish- or algae-based EPA/DHA.
Overlooking added vitamins: Cod liver oil contributes vitamins A and D. Track your total intake from all supplements and fortified foods.
Ignoring diet: If you already eat fish regularly, you may not need a high-amount EPA/DHA supplement. If you never eat fish, algal oil can be a vegetarian alternative.

Reasoning through whether you need a supplement

Ask yourself:

How often do I eat fish and seafood? If it’s 2 to 3 times per week from lower-mercury choices, I may already be getting EPA and DHA from food.
What am I trying to achieve—generally increase omega-3 intake, or replace fish because I don’t eat it? That helps determine whether fish oil or algal oil makes sense.
Do I prefer capsules or liquid, and how many capsules per day am I willing to take based on the serving size?
Are there safety issues for me (for example, anticoagulants or pregnancy) that mean I should speak with a clinician first?

Safety and when to ask for help

Side effects from omega-3 supplements can include an unpleasant taste, bad breath, heartburn, nausea, stomach discomfort, diarrhea, and headache.

Interactions: The NIH Office of Dietary Supplements notes that high intakes of EPA and DHA may increase bleeding risk when taken with warfarin or other anticoagulant medications. If you take an anticoagulant or have a bleeding disorder, consult a healthcare professional before using an omega-3 supplement.

Upper amounts from supplements: According to the NIH Office of Dietary Supplements, the U.S. Food and Drug Administration has concluded that EPA and DHA from dietary supplements are generally safe if combined intakes do not exceed 5 grams per day. This limit applies to EPA+DHA from supplements, not from food.

Fish choices: If you are pregnant, breastfeeding, or feeding young children, follow the FDA’s fish advice to choose options lower in mercury and appropriate serving sizes. If you do not eat fish, algal oil can provide DHA (and sometimes EPA).

Get professional guidance if you are pregnant or breastfeeding, plan to give omega-3 supplements to a child, have a medical condition, take prescription medicines (especially anticoagulants), or are considering high-dose omega-3 supplements.

Practical checklist before you buy

Confirm your goal: increase EPA/DHA intake because you don’t eat fish, or prefer a vegetarian option.
Review your diet: how many fish or seafood meals do you eat weekly, and are they lower-mercury choices?
Pick a source: fish/krill oil for EPA+DHA; algal oil if vegetarian; cod liver oil only if you account for vitamins A and D.
Read the panel: note serving size and the exact mg of EPA and DHA per serving.
Scan for extras: vitamins A or D in cod liver oil, other ingredients, expiration date, and storage directions.
Think quality: consider products with independent quality seals and clear manufacturer contact information.
Safety first: if you use anticoagulants, are pregnant or breastfeeding, or plan high intakes, talk to a clinician or pharmacist.

Bottom line

Compare omega-3 supplements by their EPA and DHA amounts, not the total oil. Aim to get omega-3s from food—especially fish chosen according to FDA guidance—and use supplements to fill specific gaps. If you take anticoagulants, are pregnant or breastfeeding, or are considering high-dose use, get professional advice first.