What krill oil is and why people take it
Krill oil is a supplement made from Antarctic krill, tiny shrimp-like creatures that form the base of the ocean food chain. Unlike fish oil, which comes from the tissue of larger fish, krill oil is extracted from the whole animal and contains omega-3 fatty acids bound to phospholipids—a structure that may affect how your body absorbs and uses them.
People take krill oil for the same reasons they take fish oil: the omega-3 fatty acids EPA and DHA, which appear in research to support heart health, brain function, and inflammation management. The practical difference is that krill oil also contains astaxanthin, a red pigment with antioxidant properties, and it comes in smaller capsules that some people find easier to swallow. Krill oil typically costs two to three times more per serving than standard fish oil.
Key Takeaways
- Krill oil contains the same omega-3 fatty acids as fish oil (EPA and DHA), but the body may absorb them differently because they are bound to phospholipids rather than triglycerides.
- Research shows modest benefits for heart health markers and joint inflammation, but the evidence is not stronger than what exists for fish oil at a lower price.
- Krill oil includes astaxanthin, an antioxidant that fish oil does not, though the amount per capsule is small and its practical benefit is unclear.
- Krill oil costs significantly more than fish oil and comes in smaller capsules, which matters if you are budget-conscious or have trouble swallowing pills.
- People with shellfish allergies should avoid krill oil, and it can interact with blood thinners—check with your doctor if you take those medications.
How krill oil's structure differs from fish oil
The omega-3s in krill oil are attached to phospholipids, the same molecules that make up cell membranes. Fish oil contains omega-3s in triglyceride form, which is how they naturally occur in fish tissue. This structural difference is the main reason krill oil proponents claim it is absorbed better, though the research on actual absorption is mixed.
Some studies show that phospholipid-bound omega-3s reach the bloodstream faster and in higher concentrations than triglyceride forms. Other studies find no meaningful difference in how much EPA and DHA your body actually uses. The practical takeaway: if you take krill oil and feel better, the phospholipid structure may play a role—but you cannot assume it will work better for you than fish oil just because the chemistry is different.
What the research shows about krill oil and heart health
The strongest evidence for krill oil involves cholesterol and triglyceride levels. Several small studies found that krill oil reduced triglycerides and LDL cholesterol (the kind associated with plaque buildup) while raising HDL cholesterol (the protective kind). The effect sizes were modest—typically a 5 to 15 percent improvement—and similar to what fish oil shows in comparable studies.
One frequently cited study published in the American Journal of Clinical Nutrition found that krill oil reduced triglycerides more effectively than fish oil at the same dose, but the study was small (90 participants) and funded by a krill oil manufacturer. Larger, independent studies comparing krill oil head-to-head with fish oil at equivalent omega-3 doses are rare. For heart health specifically, the evidence supports omega-3 supplementation in general, but does not clearly show that krill oil outperforms fish oil.
Joint pain and inflammation: what krill oil may help with
Several studies have looked at krill oil for joint pain and stiffness, particularly in people with osteoarthritis or rheumatoid arthritis. Participants taking krill oil reported less joint pain and swelling, and some showed improvements in inflammatory markers in their blood. Again, the effect sizes were small to moderate, and the studies involved fewer than 200 people each.
The anti-inflammatory benefit likely comes from the EPA and DHA, not from the astaxanthin or phospholipid structure specifically. If you are considering krill oil for joint pain, you should know that fish oil at a higher dose of EPA and DHA would probably produce similar results at a fraction of the cost. Krill oil may be worth trying if you have already tried fish oil and did not tolerate it well, or if the smaller capsule size matters to you.
Astaxanthin and other compounds in krill oil
Astaxanthin is a carotenoid pigment that gives krill their red color and has antioxidant and anti-inflammatory properties in laboratory studies. A typical krill oil capsule contains 0.5 to 2 mg of astaxanthin. For comparison, a serving of wild salmon contains 4 to 5 mg, and astaxanthin supplements sold separately typically provide 4 to 12 mg per capsule.
The amount of astaxanthin in krill oil is too small to produce the effects seen in astaxanthin-specific research. It is present, but it is not a reason to choose krill oil over fish oil unless you are also interested in astaxanthin for its own sake and want to avoid taking a separate supplement. Krill oil also contains choline and other phospholipids, but these are present in many foods and are not unique to krill.
Cost, dosing, and practical considerations
A month's supply of krill oil typically costs $20 to $40, while fish oil of similar omega-3 potency costs $5 to $15. The price difference reflects krill oil's lower yield per animal and higher harvesting costs. Standard krill oil capsules are smaller and softer than fish oil capsules, which some people prefer—they are easier to swallow and less likely to cause the "fish burp" aftertaste that fish oil can produce.
Most krill oil products provide 300 to 500 mg of omega-3s per capsule, so you may need to take two or three per day to match the dose used in research studies (1,000 to 2,000 mg of omega-3s daily). Check the label for the amount of EPA and DHA specifically, not just total omega-3 content. If you are on blood thinners like warfarin or clopidogrel, talk to your doctor before starting krill oil, as omega-3s can have mild blood-thinning effects.
Who should avoid krill oil
People with shellfish allergies should not take krill oil, since krill are crustaceans and cross-reactivity is possible. If you have a shellfish allergy but have tolerated fish oil without problems, krill oil is still a risk—the allergy proteins are different. Anyone with a bleeding disorder or taking anticoagulant medications should check with their doctor first.
Krill oil is not recommended during pregnancy or breastfeeding without medical guidance, though the same caution applies to fish oil. If you are vegetarian or vegan, krill oil is not an option; algae-based omega-3 supplements are the plant-based alternative. Store krill oil in a cool, dark place or in the refrigerator after opening, as the omega-3s can oxidize and become rancid if exposed to heat or light.
Krill oil versus fish oil: which makes sense for you
If your main goal is omega-3 intake for heart or joint health, fish oil is the more cost-effective choice and has more extensive research behind it. The evidence for krill oil's superiority is weak, and you can achieve similar results by taking a higher dose of fish oil for less money.
Krill oil makes more practical sense if you cannot tolerate fish oil (due to aftertaste, capsule size, or digestive upset), if you prefer smaller pills, or if you are willing to pay more for the phospholipid structure and astaxanthin content based on your own experience. Neither supplement is a substitute for a diet rich in fatty fish, regular exercise, or managing other heart disease risk factors. If you are considering either one, start with a dose of 1,000 to 2,000 mg of combined EPA and DHA daily and give it at least 8 to 12 weeks before deciding whether it is working for you.
Frequently Asked Questions
Does krill oil work faster than fish oil?
Some research suggests phospholipid-bound omega-3s reach the bloodstream faster, but this does not mean you will feel better sooner. Most benefits from omega-3 supplementation take 4 to 12 weeks to appear, whether you take krill oil or fish oil. Speed of absorption is not the same as speed of effect.
Can I take krill oil and fish oil together?
You can, but there is no reason to. Taking both would just increase your omega-3 intake and your cost without adding a benefit you would not get from taking more of one or the other. Stick with one source and adjust the dose based on the EPA and DHA content.
Is krill oil better for brain health than fish oil?
The research on omega-3s and brain health (memory, focus, mood) is stronger for fish oil than for krill oil, mainly because fish oil has been studied more extensively. Both contain EPA and DHA, the omega-3s linked to brain function. If brain health is your goal, fish oil at a proven dose is the safer, cheaper choice.
What should I look for on a krill oil label?
Check the amount of EPA and DHA listed separately, not just total omega-3 content. Look for third-party testing seals (NSF, USP, or ConsumerLab) to confirm the product contains what the label says. Verify the serving size and how many capsules you need to reach 1,000 to 2,000 mg of combined EPA and DHA daily.
Does krill oil expire or go bad?
Yes. Omega-3s oxidize over time, especially if exposed to heat, light, or air. Check the expiration date on the bottle and store krill oil in a cool, dark place or refrigerator. If it smells fishy or rancid when you open it, do not use it—oxidized omega-3s may cause digestive upset and lose their benefit.