Antarctic krill oil comes from tiny shrimp-like creatures and contains omega-3 fatty acids in a different form than fish oil
Antarctic krill oil is made from small crustaceans called krill that live in the Southern Ocean around Antarctica. The oil is extracted from these creatures and sold as a supplement. Unlike fish oil, which contains omega-3 fatty acids in the form of triglycerides, krill oil contains them as phospholipids—a different chemical structure that some research suggests the body may absorb more easily.
Krill oil also contains a compound called astaxanthin, a red pigment with antioxidant properties that fish oil does not naturally contain. This is one reason krill oil looks reddish and costs more per dose than standard fish oil supplements.
The supplement market for krill oil has grown significantly over the past 15 years, though it remains smaller than the fish oil market. People take it for similar reasons they take fish oil—to support heart health, joint function, and inflammation—but the phospholipid form and astaxanthin content are what manufacturers emphasize as the distinguishing factors.
Key Takeaways
- Krill oil contains omega-3 fatty acids in phospholipid form, which differs from the triglyceride form found in fish oil.
- Krill oil naturally includes astaxanthin, an antioxidant that gives it a red color and is not present in most fish oils.
- Research on krill oil is more limited than research on fish oil, and study results on its health effects are mixed.
- Krill oil costs significantly more per serving than fish oil, and sustainability concerns exist around krill harvesting in Antarctic waters.
How krill oil differs from fish oil at the chemical level
The main chemical difference lies in how the omega-3 fatty acids are packaged. Fish oil delivers omega-3s as triglycerides, which is the form your body naturally stores fat. Krill oil delivers them as phospholipids, which are the form found in cell membranes. Some research suggests phospholipids may cross the blood-brain barrier more easily and be incorporated into cell membranes more efficiently, though this remains an area of ongoing study.
In practical terms, this means your body may process krill oil slightly differently than fish oil. However, both forms deliver the same omega-3 fatty acids—EPA and DHA—which are the compounds most people are seeking when they take either supplement. The phospholipid structure does not change what those fatty acids do; it may only change how readily your body uses them.
Astaxanthin is the second major difference. This carotenoid pigment is produced by the algae that krill eat, which is why krill naturally contain it. Fish do not accumulate astaxanthin in the same way, so fish oil supplements do not include it unless it is added separately. Astaxanthin is marketed as a powerful antioxidant, though human research on its specific health effects remains limited.
What research shows about krill oil and health outcomes
Studies on krill oil are fewer and smaller than studies on fish oil. The research that does exist focuses mainly on cholesterol, triglycerides, and inflammation markers. Some studies have found that krill oil may help lower triglycerides and improve cholesterol ratios in people with high cholesterol, but the effect sizes are often modest and comparable to what fish oil produces.
A 2018 review in the journal Nutrients examined available krill oil studies and concluded that evidence for its benefits is "promising but limited." The review noted that most studies were short-term, involved small numbers of participants, and were partly funded by krill oil manufacturers—a detail that matters when interpreting results.
Research specifically on the phospholipid form of omega-3s is still developing. While some laboratory studies suggest phospholipids may be absorbed differently, this has not consistently translated into larger health benefits in human trials. The astaxanthin content of krill oil has been studied mostly in isolation, not as part of the whole supplement, making it difficult to know how much it contributes to any overall effect.
Cost and sustainability considerations
Krill oil supplements typically cost two to four times more per serving than fish oil supplements, depending on the brand and dose. A month's supply of krill oil can range from $20 to $60, while fish oil of similar omega-3 content usually costs $10 to $25 for the same period. The higher price reflects both the cost of harvesting krill in remote Antarctic waters and the smaller market size compared to fish oil.
Sustainability is a concern some people weigh when choosing between krill and fish oil. Krill fishing is regulated by an international body called the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), which sets catch limits. However, krill are a foundational food source for whales, penguins, and other Antarctic wildlife, so any harvest removes food from that ecosystem. The long-term effects of large-scale krill fishing are not yet fully understood.
Fish oil comes from species like anchovies and sardines, which are also wild-caught and have their own sustainability questions. Some fish oil manufacturers now use fish from farmed sources or from fisheries certified by organizations like the Marine Stewardship Council. Krill oil does not yet have equivalent certification options, though some manufacturers market their practices as responsible.
Who might consider krill oil and potential side effects
People who take fish oil and want to try an alternative, or those interested in the phospholipid form of omega-3s specifically, may consider krill oil. It is also an option for people who experience fish-flavored burps or digestive upset from fish oil, since krill oil has a milder taste and some people report fewer gastrointestinal side effects, though this varies by individual.
Krill oil is generally considered safe for most adults at standard doses (typically 500 to 2,000 mg per day). Common side effects are mild and similar to fish oil: upset stomach, nausea, or loose stools. People taking blood thinners like warfarin should discuss omega-3 supplements with their doctor before starting, as high doses may increase bleeding risk. Pregnant or nursing people should also check with their healthcare provider before adding any new supplement.
Krill oil is not recommended for people with shellfish allergies, since krill are crustaceans. Even though the oil is processed, trace proteins may remain, and reactions are possible.
How to read krill oil labels and choose a product
Krill oil labels should list the amount of EPA and DHA per serving, just as fish oil labels do. This is the most important number to compare across products, since the omega-3 content varies. A typical krill oil supplement contains 100 to 300 mg of combined EPA and DHA per capsule, though some products contain more.
Labels should also state whether the product has been third-party tested for purity and contaminants. Organizations like NSF International, USP, or ConsumerLab conduct these tests and verify that the product contains what the label says and is free of heavy metals and other pollutants. This testing is voluntary, but it is a sign that a manufacturer stands behind the product.
The astaxanthin content may be listed separately on the label, usually in milligrams. If you are interested in krill oil specifically for the astaxanthin, check this number; it varies widely between brands. Some products contain 0.5 mg per serving, while others contain 2 mg or more.
Krill oil versus fish oil: which might be right for you
The choice between krill oil and fish oil often comes down to personal factors rather than a clear scientific winner. If cost is a primary concern, fish oil is the more economical choice and has decades of research behind it. If you want to explore the phospholipid form of omega-3s or prefer a supplement with natural astaxanthin, krill oil is worth trying—though the evidence that these differences produce noticeably better results is still developing.
Some people take both, rotating between them or combining them. Others find that one sits better in their stomach than the other. Since both deliver omega-3 fatty acids and both are generally safe, the "best" choice is often the one you will take consistently and that fits your budget.
If you are new to omega-3 supplements and unsure whether krill oil or fish oil is right for you, starting with fish oil is a reasonable approach—it is less expensive, more widely studied, and easier to find. You can always switch to krill oil later if you want to experiment with the different form or if you experience side effects with fish oil.
Frequently Asked Questions
Is krill oil better absorbed than fish oil?
Some research suggests the phospholipid form in krill oil may be absorbed differently, but studies have not consistently shown that this translates to better health outcomes in humans. Both forms deliver omega-3 fatty acids effectively; the difference in absorption is still being studied.
Does krill oil really contain more antioxidants?
Krill oil naturally contains astaxanthin, which fish oil does not. However, astaxanthin's specific health benefits in humans are not yet well established. You can also buy fish oil with added astaxanthin if you want both supplements in one product.
Can I take krill oil if I am allergic to shellfish?
Krill are crustaceans, so krill oil is not recommended for people with shellfish allergies. Even though the oil is processed, trace proteins may remain and trigger a reaction. Talk to your doctor before trying it.
How long does it take to notice effects from krill oil?
Most omega-3 supplements, including krill oil, take several weeks to several months to show measurable effects on cholesterol or inflammation markers. You will not feel an when ready difference; any benefits develop gradually.
Why is krill oil so much more expensive than fish oil?
Krill oil costs more because krill are harvested from remote Antarctic waters, which is expensive, and because the market is smaller. Fish oil production is larger and more established, which keeps costs lower.