Fish Oil vs. Algae Oil

How to compare EPA and DHA, choose a supplement that fits your needs, and tell whether you’re paying for more omega-3 or simply more oil.

Pick up a bottle of fish oil and you might see 1,000 mg in large type. Next to it is an algae oil supplement that says 500 mg. The fish oil looks twice as strong, but turn the bottles around. If the fish oil provides 300 mg of EPA and DHA combined and the algae oil provides 400 mg, the algae oil delivers more of those two omega-3s per serving. The front labels were measuring something different. Health Professional Fact Sheet

Fish oil and algae oil can both supply EPA and DHA. Fish oil commonly contains both, while some algae oils are primarily DHA and others provide a meaningful amount of EPA as well. The better choice depends on why you’re taking it, how much of each fatty acid the product contains, and whether it fits your diet and budget. If a clinician recommended an omega-3 product for a medical condition, start with their instructions before comparing bottles. Health Professional Fact Sheet

Where do fish oil and algae oil come from?

Fish oil is extracted from fish and can be processed to concentrate its omega-3 fatty acids. A standard fish oil capsule may contain a modest amount of EPA and DHA, while a concentrate can deliver more in a similar amount of oil. That’s why two fish oil products with the same capsule size can have different amounts of omega-3. Health Professional Fact Sheet

Algae oil, often called algal oil, is made from microalgae. Microalgae are where the EPA and DHA found in marine food chains originate. Fish accumulate these fatty acids through the food they eat. An algae oil supplement gets them from microalgae directly, making it an option for people who avoid fish. Check the capsule and other ingredients if you want the entire product to be vegan. A fish-free oil can still come in an animal-derived gelatin capsule. Health Professional Fact Sheet

The source helps you narrow the field. The Supplement Facts panel tells you how the products you’re considering actually compare. Health Professional Fact Sheet

EPA, DHA, and ALA explained

EPA, short for eicosapentaenoic acid, and DHA, short for docosahexaenoic acid, are long-chain omega-3 fatty acids. DHA is a component of cell membranes in the brain and retina. Both EPA and DHA are used throughout the body. Supplements can deliver one or both, so a label that says only “omega-3” leaves out a detail that may matter to your decision. Health Professional Fact Sheet

ALA, or alpha-linolenic acid, is an essential omega-3 found in foods such as flaxseed, chia seeds, walnuts, and some plant oils. The body can convert some ALA into EPA and then DHA, but conversion is limited. Flaxseed oil and algae oil can both fit a plant-based diet, while providing different fatty acids. If you want a direct source of DHA or EPA, look for those names on the label. Health Professional Fact Sheet

There’s a practical difference between shopping for DHA specifically and shopping for EPA and DHA combined. A DHA-focused algae oil might make sense if that’s what you were advised to take. If you were advised to get both, check each line. Two products can have the same combined total but different amounts of EPA and DHA. Health Professional Fact Sheet

Is algae oil absorbed as well as fish oil?

Both sources can raise EPA and DHA levels in the body. In one randomized study, researchers compared specific microalgal and fish oil formulations in adults and measured EPA and DHA in blood phospholipids over 14 weeks. The findings supported comparable bioavailability for the formulations studied after accounting for intake. For someone choosing a fish-free source, that provides evidence that the body can absorb and incorporate these fatty acids from microalgal oil. PubMed

The study measured fatty acid levels in blood. It didn’t compare whether people had fewer heart attacks, better memory, or other long-term health outcomes. It also didn’t test every formulation on the market. If one bottle gives you 100 mg of DHA and another gives you 400 mg, a study showing comparable absorption doesn’t make those servings equivalent. Check the amount first, then consider the formulation, evidence, and how well you tolerate it. Health Professional Fact Sheet

How to compare fish oil and algae oil labels

1. Check how many capsules make a serving

A serving might be one softgel, two capsules, or a measured amount of liquid. Start there before comparing milligrams. If a label lists 600 mg of EPA and DHA per two-capsule serving, one capsule supplies about 300 mg combined. That distinction matters if you expect to take one capsule or are calculating how long the bottle will last. ods.od.nih.gov

2. Find EPA and DHA separately

A label can list total oil, total omega-3, and EPA and DHA. These are three different measurements. Total oil includes all the fats in the oil. Total omega-3 can include fatty acids beyond EPA and DHA. If EPA and DHA are what you’re comparing, use the lines that name them. When only DHA is listed, you know how much DHA you’re getting, but you can’t assume there’s a meaningful amount of EPA. Health Professional Fact Sheet

Here’s a worked example. The amounts and prices are hypothetical.

In this example, the fish oil gives you more combined EPA and DHA per serving. The algae oil gives you more DHA per serving and more combined EPA and DHA per softgel, because its serving is one softgel. It also costs less per labeled serving despite having a higher bottle price. Which comparison matters depends on what you’re looking for.

If two products offer a similar EPA-to-DHA profile, you can also compare cost per gram of combined EPA and DHA. In the example, the fish oil costs $1.00 per gram and the algae oil costs $1.25 per gram. That calculation can help when you’re comparing similar products, but it can hide differences that matter. If you’re looking for DHA specifically, compare the amount and cost of DHA rather than treating every milligram of EPA and DHA as interchangeable.

3. Look for quality information you can verify

Check whether the manufacturer identifies who made the product, provides contact information, and includes a lot number. If it advertises third-party testing, ask what was tested. Potency, contaminants, and oxidation are different checks. If there’s a certification seal, look up the exact product in the certifier’s directory. If you’re given a test report, see whether its lot number matches the bottle you’re buying. A quality check can help you assess what’s in a product. Evidence that it helps with your goal comes from a different kind of testing. ods.od.nih.gov

Follow the storage instructions, particularly for liquid oils that may have different directions after opening. Check the date on the bottle, and think about whether you’ll finish it in a reasonable time. A bigger bottle may have a better price per serving and still be a poor buy if you dislike the taste or rarely use it.

What are you taking omega-3 for?

To get EPA or DHA when you don’t eat fish

If you avoid fish for dietary, ethical, or taste reasons, algae oil gives you a direct source of DHA and, depending on the formula, EPA. Start by deciding which fatty acid you want and why. Then compare products that disclose the amounts clearly. If you already eat fish regularly, ask what a supplement would add before buying one. Fish provides other nutrients, including protein, that an oil capsule doesn’t supply. Health Professional Fact Sheet

To support heart health

Omega-3s have been studied for several cardiovascular outcomes. Results depend on the product, the dose, and the people taking it. In the large VITAL trial, a marine omega-3 supplement did not significantly reduce the primary combined outcome of major cardiovascular events in the general population studied. Other trials have looked at specific prescription products in people at higher risk. A result for one product and patient group doesn’t tell you what to expect from any bottle labeled “heart support.” Health Professional Fact Sheet

If your clinician is treating high triglycerides, ask whether they’re recommending a prescription omega-3 medication or a dietary supplement. Prescription products have specified formulations and doses, and some are used for particular cardiovascular indications. An over-the-counter fish oil or algae oil supplement shouldn’t be substituted on the basis of the total oil amount on the front label. Health Professional Fact Sheet

To support memory or brain health

DHA is part of brain cell membranes, which helps explain why it’s studied in relation to cognition. A trial still has to show that taking a supplement changes the outcome you care about. In AREDS2, omega-3 supplementation did not significantly improve cognitive outcomes over approximately five years in the older adults studied. If memory problems are new, worsening, or affecting everyday life, discuss those changes with a clinician. Comparing fish oil and algae oil won’t tell you what’s causing them. Health Professional Fact Sheet

During pregnancy or breastfeeding

The FDA and EPA advise people who are pregnant or breastfeeding to eat 8–12 ounces per week of a variety of lower-mercury fish from their Best Choices category. If you don’t eat fish, ask your prenatal care team whether a DHA supplement makes sense and whether your prenatal vitamin already contains it. DHA from algae is a fish-free option to discuss. Health Professional Fact Sheet

Check whether a product is ordinary fish oil or cod liver oil. Cod liver oil can contain vitamins A and D in addition to omega-3s. During pregnancy, the amount of preformed vitamin A matters, especially if you’re already taking a prenatal supplement. Bring the labels for both products to your prenatal care team before combining them. Health Professional Fact Sheet

Side effects and safety considerations

Omega-3 supplements can cause aftertaste, burping, heartburn, nausea, or other digestive symptoms. If you dislike the taste of fish oil, algae oil may be worth comparing. You can also check the number and size of the capsules. A product you can comfortably take as directed may fit your routine better than one that looks more concentrated on paper. Health Professional Fact Sheet

Talk with a healthcare professional before using high-dose omega-3 supplements, particularly if you take an anticoagulant or have a history of atrial fibrillation. Some large trials using high-dose omega-3 products found a small increase in atrial fibrillation among people with cardiovascular disease or at high cardiovascular risk. Tell your care team about your supplements if you’re planning a procedure, and ask what to do with each one. Health Professional Fact Sheet

If you have a fish allergy, ask your allergy clinician before using fish oil. Algae oil avoids fish as the oil source, but you’ll still want to check the complete ingredient list and ask about possible cross-contact if that matters for your allergy. If a product causes trouble breathing or swelling of the lips, tongue, or throat, seek emergency help. www.fda.gov

Common questions about fish oil and algae oil

Is algae oil automatically better for the environment?

Algae oil can be produced without harvesting fish for the oil itself. If environmental impact matters to you, compare what the manufacturers disclose about sourcing, production, and independent verification. For fish oil, look for information about the fishery and whether the oil comes from fish-processing byproducts. For algae oil, look for information about how the algae are grown and processed. The source tells you where the oil came from. A broader environmental comparison needs more information about how each product was made. Health Professional Fact Sheet

Do I need both fish oil and algae oil?

For most shoppers comparing the two as sources of EPA and DHA, one suitable product can cover the intended role. Taking both can make it harder to keep track of the total. Also check whether a prenatal vitamin, multivitamin, or another product already contains omega-3s. If you’ve been given a specific plan, ask whether it calls for EPA, DHA, or both and how much you should get from each product. Health Professional Fact Sheet

Should I look for a particular EPA-to-DHA ratio?

The ratio is only one piece of information. A product can advertise a 2:1 EPA-to-DHA ratio while giving you 100 mg of EPA and 50 mg of DHA, or 600 mg of EPA and 300 mg of DHA. Those are the same ratio and very different amounts. Start with the milligrams of each. If your clinician recommended a particular dose or formulation, compare the product with that recommendation. Health Professional Fact Sheet

Which one should you choose?

Choose algae oil if you want a fish-free source and the product provides the EPA, DHA, or combination you’re looking for. Check the capsule if you want a vegan product. Choose fish oil if fish-derived ingredients suit you and you find a product that supplies the amounts you want at a cost you’re comfortable with. If you’re buying omega-3 for a medical reason, confirm the exact product and dose with your clinician. Health Professional Fact Sheet

When you have two bottles in front of you, write down EPA per serving, DHA per serving, capsules per serving, and servings per bottle. Then check the price and any quality claims you can verify. Those details will tell you which bottle fits your needs far more clearly than the largest number printed on the front.