What Is Krill Oil?

A supplement for heart health and inflammation

Krill oil is an oil derived from shrimp-like crustaceans called krill. The omega-3-rich oil contains two of the same essential fatty acids as fish oil (eicosapentaenoic acid, or EPA, and docosahexaenoic acid, or DHA). The EPA and DHA in krill oil are said to have higher bioavailability (rate of absorption) compared to fish oil because much of the EPA and DHA in krill oil is bound to phospholipids.

For years, people have been taking fish oil supplements for the essential fatty acids contained inside, and more and more people have been turning to krill oil as an alternative. Its rise in popularity has raised some concerns about sustainability.

krill oil vs. fish oil
Verywell / JR Bee

What Is Krill Oil Used For?

Krill oil is often used for the same reasons as fish oil: to improve heart health and fight inflammation. Compared to fish oil, krill oil contains higher amounts of astaxanthin—a carotenoid pigment that gives krill and other crustaceans their characteristic red-pink color. Unlike many other antioxidant substances, preliminary studies have found that astaxanthin may cross the blood-brain barrier and protect the brain and central nervous system from free radical damage.

Hearth Health

More research is needed to tease out the effects of krill oil on heart health. A study published in Alternative Medicine Review examined 120 people with hyperlipidemia (too many fats in the blood) who were given one of the following: a daily dose of 2 to 3 grams (g) of krill oil; 1 to 1.5 g of krill oil; fish oil containing 180 milligrams (mg) EPA and 120 mg DHA; or a placebo. Krill oil dosages were dependent on body mass index (BMI).

Krill oil (1 to 3 g/day) was found to be effective for the reduction of total cholesterol, LDL cholesterol, and triglycerides and the increasing of HDL cholesterol levels compared to fish oil and the placebo.

A 2011 study published in Lipids compared the effects of krill oil (543 mg of combined EPA and DHA), fish oil (864 mg of combined EPA and DHA), or no supplementation on people with normal or slightly elevated cholesterol levels. After seven weeks of supplementation, there was an increase in blood levels of EPA and DHA in both the krill and fish oil groups, but there were no significant changes in any of the blood lipids or markers of oxidative stress and inflammation.


A study in the Journal of the American College of Nutrition examined krill oil (300 mg daily) compared to a placebo and found that 30 days of krill oil supplementation was effective at reducing symptoms of rheumatoid arthritis and C-reactive protein (a marker of inflammation). Specifically, there was a 20.3 percent to 28.9 percent symptom reduction and 31.6 percent less rescue medication usage.

According to a 2007 review, taking 1g of krill oil twice a day for 90 days resulted in a significant reduction of premenstrual syndrome (PMS) symptoms, one of the main causes of which is thought to be inflammation. This is promising, but more research is still needed.

Possible Side Effects

Side effects of krill oil may include:

  • Loose stools
  • Diarrhea
  • Indigestion
  • Bloating
  • Oily skin

Krill oil isn't known to cause a fishy aftertaste or belching, which often happens with fish oil.

Interactions and Contraindications

People with bleeding disorders and those taking medication or supplements that may increase the risk of bleeding such as aspirin, warfarin, heparin, clopidogrel, garlic, ginkgo biloba, or non-steroidal anti-inflammatory medications (NSAIDS) such as ibuprofen or naproxen should only use krill oil under a physician's supervision.

People with allergies to seafood shouldn't use krill oil. It also shouldn't be taken two weeks before or after surgery.

The safety of supplements in pregnant women, nursing mothers, and children has not been established. Likewise, it is not known whether there are other medical conditions or medications that may contraindicate the use of krill oil. It is best to talk with your primary care provider before taking this supplement.

Dosage and Preparation

Krill oil supplements tend to be available in the form of capsules from most supplement stores. Capsule dosages are designed so that 1 to 3g of oil can be taken daily. Sometimes the dosages are listed in terms of EPA and DHA content.

In order to start seeing a benefit from taking krill oil supplements, it may be necessary to consistently take the capsules twice daily for up to eight to 12 weeks. This is what is known as a tonic, rather than an acute supplement. That is, it is meant to be incorporated into your normal nutritional routine so that you may see benefits over time.

Due to the more efficient bioavailability of krill oil, 660 mg of EPA and DHA from krill oil may be sufficient to achieve the same effects as 1000 mg of EPA and DHA from fish oil.

What to Look For

The recent popularity of krill oil supplements has raised serious concerns that it could threaten populations of its predators, including penguins, seals, and whales.

Besides nutritional supplements, commercially fished krill are used for aquaculture and aquarium feeds, sport fishing bait, and for food consumption. In Japan, krill is considered a delicacy and is called okiami. In 2010, Whole Foods Market stopped selling krill oil supplements, citing environmental concerns.

It is important to purchase krill oil supplements that are certified as coming from sustainable sources. Look for a label certifying that the krill oil contained in the product comes from an MSC- and Friends of the Sea-certified sustainable fishery. This ensures that harvesting practices were subject to oversight by the Commission on the Conservation of Antarctic Marine Living Resources, which is working to protect 1.5 million square kilometers of krill habitat in collaboration with 24 countries and the European Union.

Was this page helpful?
13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Ramprasath VR, Eyal I, Zchut S, Shafat I, Jones PJ. Supplementation of krill oil with high phospholipid content increases sum of EPA and DHA in erythrocytes compared with low phospholipid krill oilLipids Health Dis. 2015;14:142. doi:10.1186/s12944-015-0142-y

  2. Ambati RR, Phang SM, Ravi S, Aswathanarayana RG. Astaxanthin: sources, extraction, stability, biological activities and its commercial applications--a reviewMar Drugs. 2014;12(1):128–152. doi:10.3390/md12010128

  3. Bunea R, El farrah K, Deutsch L. Evaluation of the effects of Neptune Krill Oil on the clinical course of hyperlipidemia. Altern Med Rev. 2004;9(4):420-8.

  4. Ulven SM, Kirkhus B, Lamglait A, et al. Metabolic effects of krill oil are essentially similar to those of fish oil but at lower dose of EPA and DHA, in healthy volunteersLipids. 2011;46(1):37–46. doi:10.1007/s11745-010-3490-4

  5. Deutsch L. Evaluation of the effect of Neptune Krill Oil on chronic inflammation and arthritic symptoms. J Am Coll Nutr. 2007;26(1):39-48. doi:10.1080/07315724.2007.10719584

  6. Goldberg RJ, Katz J. A meta-analysis of the analgesic effects of omega-3 polyunsaturated fatty acid supplementation for inflammatory joint pain. Pain. 2007;129(1-2):210-23. doi:10.1016/j.pain.2007.01.020

  7. Ulven SM, Holven KB. Comparison of bioavailability of krill oil versus fish oil and health effectVasc Health Risk Manag. 2015;11:511–524.doi:10.2147/VHRM.S851 65

  8. Delaney JA, Opatrny L, Brophy JM, Suissa S. Drug drug interactions between antithrombotic medications and the risk of gastrointestinal bleedingCMAJ. 2007;177(4):347–351. doi:10.1503/cmaj.070186

  9. Schweitzer A. Dietary supplements during pregnancyJ Perinat Educ. 2006;15(4):44–45. doi:10.1624/105812406X107834

  10. Rundblad A, Holven KB, Bruheim I, Myhrstad MC, Ulven SM. Effects of krill oil and lean and fatty fish on cardiovascular risk markers: a randomised controlled trialJ Nutr Sci. 2018;7:e3. doi:10.1017/jns.2017.64

  11. Bradberry JC, Hilleman DE. Overview of omega-3 Fatty Acid therapiesP T. 2013;38(11):681–691.

  12. Huang T, Sun L, Stark J, et al. Relative changes in krill abundance inferred from Antarctic fur sealPLoS One. 2011;6(11):e27331. doi:10.1371/journal.pone.0027331

  13. Nichols PD, Petrie J, Singh S. Long-chain omega-3 oils-an update on sustainable sourcesNutrients. 2010;2(6):572–585. doi:10.3390/nu2060572

Additional Reading