Krill oil is an omega-3 supplement. It contains the same two key omega-3 fatty acids found in fish oil, EPA and DHA, but delivers them in a different chemical form that may affect how your body absorbs them. A typical krill oil product contains roughly 15% EPA and 8% DHA by weight, meaning a standard 1,000 mg capsule provides around 150 mg of EPA and 84 mg of DHA.
How Krill Oil Delivers Omega-3s Differently
The omega-3s in fish oil are mostly bound to triglycerides, a type of fat. Krill oil carries a significant portion of its omega-3s bound to phospholipids instead, about 40% of its fatty acid content. Phospholipids are the same type of molecule that makes up your cell membranes, which is why some researchers believe the omega-3s in krill oil mix more easily into cells and get absorbed more efficiently.
The remaining omega-3s in krill oil are split between triglycerides (around 29%) and ethyl esters (around 18%). This mix of delivery forms is one of the main reasons krill oil is marketed as a premium alternative to standard fish oil, even though the total amount of EPA and DHA per capsule is typically lower.
Krill Oil vs. Fish Oil: Omega-3 Amounts
Here’s the practical tradeoff: a single fish oil capsule (1,000 mg) often contains 300 to 500 mg of combined EPA and DHA. A krill oil capsule of the same size delivers roughly 230 mg. That means you generally need more krill oil capsules to match the same omega-3 dose you’d get from fish oil. Whether the phospholipid form compensates for the lower concentration by improving absorption is still debated, but most clinical trials on krill oil use doses of 1 to 4 grams per day to achieve measurable effects.
For heart health specifically, the American Heart Association recommends about 1 gram of combined EPA and DHA daily for cardiovascular protection. Getting that from krill oil alone would require roughly four to five standard capsules. For lowering triglycerides, where at least 2 grams of EPA and DHA per day is the typical target, krill oil becomes a more expensive and pill-heavy route compared to concentrated fish oil.
What Else Is in Krill Oil
Beyond omega-3s, krill oil contains astaxanthin, a naturally occurring pigment that gives the oil its deep red color. Astaxanthin is an antioxidant, and its presence in krill oil serves a dual purpose: it helps protect the omega-3 fatty acids in the capsule from oxidizing (going rancid), and it may offer its own health benefits related to reducing oxidative stress in the body. Krill oil also contains small amounts of vitamins, minerals, and flavonoids, though omega-3s and phospholipids are the primary active components.
Mercury and Contaminant Levels
One of the most common selling points for krill oil is purity. Antarctic krill are tiny crustaceans that sit near the bottom of the food chain in cold Southern Ocean waters, far from industrial pollution. Because they’re small and short-lived, they don’t accumulate mercury the way larger predatory fish do. Testing of commercial krill oil products has confirmed that mercury and cadmium levels consistently fall within safe limits set by international food standards.
That said, the picture isn’t entirely clean. A study analyzing multiple commercial krill oil brands found that nearly all products exceeded tolerable limits for lead, and most exceeded limits for arsenic as set by international food safety standards. These aren’t levels that pose an acute risk, but they do challenge the blanket claim that krill oil is free from contaminant concerns. If purity is your primary reason for choosing krill oil over fish oil, it’s worth looking for brands that publish independent third-party testing results.
Dosage for Different Goals
Clinical studies on krill oil have tested a fairly wide dosage range depending on the health outcome being measured:
- General omega-3 intake: 500 mg to 1 gram daily is a common maintenance dose, though the omega-3 content at this level is modest.
- Cholesterol and triglycerides: Studies have used 500 mg to 4 grams daily for 4 to 12 weeks. A meta-analysis found that at least 12 weeks of supplementation is likely needed to see improvements in triglycerides, total cholesterol, and LDL. For raising HDL, doses of at least 2 grams per day appear necessary.
- Joint discomfort: A controlled trial using 2 grams daily for 4 weeks in adults with mild knee pain showed only limited improvement in subjective symptoms compared to placebo.
Blood Thinners and Krill Oil
Because omega-3 fatty acids have mild blood-thinning properties, a common concern is whether krill oil interacts with anticoagulant medications like warfarin. A retrospective study of patients taking warfarin for atrial fibrillation and deep vein thrombosis found that fish and krill oil supplementation did not significantly affect how well warfarin controlled blood clotting, nor did it increase the incidence of bleeding events. That’s reassuring, though anyone on blood-thinning medication should still discuss supplementation with their prescriber, since individual responses can vary.
Sustainability of Krill Harvesting
Antarctic krill is one of the most abundant animal species on Earth by total biomass, but the fishery is under growing pressure. Catches in the southwest Atlantic reached approximately 500,000 metric tons in the 2023/24 fishing season, and the regulatory framework is showing cracks. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has long managed krill harvesting with strict rules about where and when fishing can occur, designed to protect penguins, whales, and seals that depend on krill. Part of that management framework expired in November 2024 after member nations failed to reach agreement, meaning the interim catch limit of 620,000 tons can now be taken from any location at any time, including areas critical to krill predators.
Voluntary industry measures help distribute catches to some extent, but they aren’t enforceable. If sustainability matters to you, look for krill oil brands certified by the Marine Stewardship Council (MSC), which requires independent verification of responsible harvesting practices.