Fish oil, krill oil and algae oil are three ways to get the same nutrients: the long-chain omega-3 fats EPA and DHA. The main differences come down to the source, the chemical form of the fat, and a few practical factors like allergies, cost per dose, and whether the product fits a vegetarian or vegan diet.
None of the three is universally "better." Fish oil is the most studied and widely available option, krill oil comes in a form some research suggests may absorb slightly differently, and algae oil is the only plant-based source of preformed EPA and DHA.
What each oil actually is
Fish oil is extracted from oily fish such as anchovy, sardine, mackerel or salmon. The EPA and DHA in fish oil are mostly bound to triglycerides, the same form fat takes in food, though some products are processed into an ethyl ester or re-esterified triglyceride form for higher concentration.
Krill oil comes from small shrimp-like crustaceans harvested mainly from Antarctic waters. Its EPA and DHA are attached to phospholipids rather than triglycerides, and krill oil also naturally contains a reddish antioxidant called astaxanthin.
Algae oil is made from microalgae grown in controlled tanks, the same organisms that fish ultimately get their omega-3s from in the food chain. It is the only common supplement source of EPA and DHA that does not involve fish or shellfish at all.
Absorption and form: does it matter?
The chemical form of omega-3 fat, whether triglyceride, ethyl ester or phospholipid, affects how efficiently the body absorbs it, but the research comparing forms head-to-head has produced mixed results. Some studies suggest phospholipid-bound omega-3s, like those in krill oil, may be absorbed somewhat differently than triglyceride-bound fats, but the evidence is not consistent enough to call one form clearly superior for everyone.
In practical terms, taking any omega-3 supplement with a meal that contains some fat tends to improve absorption, regardless of the source. If absorption is a concern, look at the total milligrams of EPA and DHA per serving on the label rather than assuming one oil type automatically outperforms another.
Fish oil, krill oil and algae oil side by side
This table summarizes the main practical differences. We cover how to check EPA and DHA amounts on a label in a separate guide.
| Factor | Fish oil | Krill oil | Algae oil |
|---|---|---|---|
| Source | Small oily fish | Antarctic krill | Cultivated microalgae |
| Omega-3 form | Mostly triglyceride or ethyl ester | Mostly phospholipid | Triglyceride |
| Contains fish/shellfish protein | Yes (fish) | Yes (shellfish) | No |
| Typical EPA:DHA balance | Varies by fish, often EPA-dominant | Varies, often EPA-dominant | Often DHA-dominant, varies by product |
| Vegetarian or vegan friendly | No | No | Yes |
| Extra compounds | None notable | Astaxanthin (antioxidant) | None notable |
Who should consider krill oil or algae oil instead of fish oil
People with a shellfish allergy should avoid krill oil, since it comes from a crustacean and can trigger the same reaction as shrimp or crab. Fish oil is generally not a concern for shellfish allergy, but anyone with a true fish allergy should avoid both fish oil and, to be cautious, ask a pharmacist before trying krill oil as well.
Algae oil is the clear choice for people who follow a vegetarian or vegan diet, or who simply prefer not to consume marine animal products. It is also worth considering if you are concerned about the sustainability of wild-caught fish stocks, since algae is farmed rather than harvested from the ocean.
Fish oil remains a reasonable default for most people because it is well studied, widely available, and usually offers more EPA and DHA per dollar than krill or algae oil, which tend to cost more per milligram of omega-3.
Other things worth checking before you choose
Beyond the source, a few label details matter more for day-to-day use than the type of oil itself.
- Look for a Health Canada Natural Product Number (NPN) on the label, which means the product has been reviewed for quality and label accuracy.
- Check the actual EPA and DHA content per serving, not just the total fish, krill or algae oil weight; these numbers can differ a lot between brands.
- Store any fish, krill or algae oil supplement away from heat and light, and check for a fishy or rancid smell, which can signal the oil has oxidized.
- If you are pregnant, breastfeeding, or taking blood thinners, talk to a doctor or pharmacist before starting any omega-3 supplement.
The short version
- Fish oil, krill oil and algae oil all provide EPA and DHA, just from different sources and in different chemical forms.
- Krill oil's phospholipid form may absorb somewhat differently than fish oil, but evidence comparing the two head-to-head is mixed.
- Algae oil is the only vegetarian and vegan source of preformed EPA and DHA.
- Krill oil should be avoided with a shellfish allergy; fish oil should be avoided with a fish allergy.
- Whichever source you pick, check the actual EPA and DHA amount per serving and look for an NPN on the label.
Shop the products
Frequently asked questions
Is krill oil really better absorbed than fish oil?
Some research suggests the phospholipid form in krill oil may be absorbed somewhat differently than the triglyceride or ethyl ester forms in fish oil, but results across studies are mixed. There is not enough consistent evidence to say krill oil is clearly superior for everyone.
Can algae oil provide enough EPA and DHA on a vegan diet?
Algae oil is the main way vegans and vegetarians can get preformed EPA and DHA, since these fats are otherwise found mainly in fish and seafood. Check the label for the combined EPA and DHA amount per serving, since this varies between products.
Is krill oil safe if I have a shellfish allergy?
No. Krill are crustaceans, so krill oil can trigger a reaction in people with shellfish allergies. Choose fish oil or algae oil instead, and speak with a pharmacist if you are unsure.
Does the source of omega-3 change how much I need?
No, the target is the same total EPA and DHA regardless of source. We break down how much EPA and DHA most adults look for in a separate guide.
Why does krill oil sometimes cost more than fish oil?
Krill are harvested in smaller volumes from specific Antarctic fisheries, and processing phospholipid-bound omega-3s is more involved, which tends to raise the cost per milligram compared with standard fish oil.
Keep reading
- Omega-3 Explained: EPA, DHA and How Much You Need
- How to Read a Fish Oil Label: A Canadian Buyer's Guide
- CoQ10: Ubiquinone vs Ubiquinol Explained
- Heart Health Basics: Where Supplements Really Fit In
Sources
- NIH Office of Dietary Supplements: Omega-3 Fatty Acids
- Health Canada: Licensed Natural Health Products Database
- Health Canada: Dietary Reference Intakes tables
This article is for general information only and is not medical advice. Talk to your doctor or pharmacist before starting a supplement, especially if you are pregnant or breastfeeding, take medication, or have a health condition.