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Overview: Krill oil, which comes from small shrimp-like creatures called krill, is available over the counter as a supplement. It may be used to increase your levels of omega-3 fatty acids and other nutrients. Common side effects may include having a bad taste in your mouth or bad breath, heartburn, nausea, upset stomach, and diarrhea. Before taking krill oil, tell your health care provider about all of your health conditions, including any food allergies, and medicines or supplements you may be using.

Uses

What is krill oil used for?

Krill oil is commonly used to raise the levels of omega-3 fatty acids and certain vitamins in your body. However, its benefits are not well defined.

Note: The FDA has not reviewed krill oil for safety and effectiveness. Learn more about dietary supplements here.

How does krill oil work (mechanism of action)?

Krill oil is made from a type of crustacean called krill. These creatures, which are similar to shrimp, grow up to about 2 inches long and contain large amounts of omega-3 fatty acids. Krill are an important food source for fish, whales, penguins, and other sea creatures.

Krill oil contains docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the omega-3 fatty acids found in fish oil. But unlike fish oil, the fatty acids in krill oil are in the form of phospholipids. It is thought that phospholipids may be absorbed better by your body. But some research has found no difference between the way your body absorbs omega-3 fatty acids from krill oil and fish oil. Also, fish oil usually contains much larger amounts of DHA and EPA than krill oil. In the United States, most people get enough omega-3 fatty acids from their diet, including from fish and some fortified foods. For example, most people can get enough DHA and EPA by eating two to three servings of low-mercury fish each week.

Krill oil also contains small amounts of other nutrients, such as vitamin A, vitamin E, and astaxanthin. Vitamins A and E are fat-soluble vitamins that perform many important functions in your body. Astaxanthin is a type of nutrient called a carotenoid that does not have any known functions in your body. However, it may help ease swelling (inflammation) and also work as an antioxidant.

Since krill oil may only contain small amounts of these nutrients, it is not clear if taking krill oil can increase the levels of these nutrients in your body by a meaningful amount. Additionally, the amounts of each nutrient in a specific krill oil product may vary. Different amounts of these nutrients may change the effects of krill oil on your body. Some krill oil dietary supplements contain a specific amount of only some of these nutrients.

How should I store krill oil?

You should store krill oil as directed on the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of krill oil?

The most common side effects of krill oil are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

  • Bad taste in your mouth or bad breath
  • Heartburn
  • Nausea, upset stomach, or diarrhea
  • Sweat that smells bad

There may be other side effects of krill oil that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of krill oil?

While less common, the most serious side effects of krill oil are described below, along with what to do if they happen.

Severe Allergic Reactions. Krill oil may cause allergic reactions, which can be serious. Stop taking krill oil and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives, which can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use krill oil?

Allergies to Ingredients. People who are allergic to any of the following should not take krill oil.

  • Krill oil
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific krill oil products they stock.

What should I know about krill oil before using it?

Krill oil is a dietary supplement. It cannot be marketed to treat or cure a disease.

Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

Keep krill oil out of the reach of children.

Krill oil naturally contains many different chemicals and nutrients. The amount of each nutrient in a specific krill oil product can change for many reasons, including the area where the krill lived, the weather conditions at that time, and the way the oil was processed. If you switch to a new bottle or a different brand, you may not have the same effects or side effects because of this variability. Talk to your health care provider if you have questions or concerns.

The FDA has not tested krill oil products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using krill oil?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if krill oil is right for you.

In particular, make sure that you discuss any of the following.

Fish or Shellfish Allergy. Krill oil is made from krill, which is a type of shellfish (crustacean). If you are allergic to shellfish, such as shrimp, crab, lobster, oysters, or scallops, you may also be allergic to krill. Before taking krill oil, tell your health care provider if you are allergic or think that you may be allergic to shellfish.

Pregnancy. It is not known if or how krill oil could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. Many of the nutrients in krill oil pass into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does krill oil interact with foods or drinks?

There are no known interactions between krill oil and foods or drinks.

It is unknown if drinking alcohol will affect krill oil.

Does krill oil interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

The interactions between krill oil and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with krill oil is incomplete. Always check with your health care provider before taking krill oil with any medicines.

Overdose/Missed Dose

What should I do if I accidentally use too much krill oil?

If you or someone else has used too much krill oil, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Krill oil products may contain many different nutrients, including omega-3 fatty acids and some vitamins. Read the product label closely and speak with a health care provider about how to take krill oil safely. Do not take double or extra doses, even if you miss a dose.