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Overview: Cod liver oil is available over the counter as a supplement. It may be used to increase the levels of omega-3 fatty acids, vitamin A, and vitamin D in your body. Common side effects include having a bad taste in your mouth or bad breath, heartburn, nausea, upset stomach, and diarrhea. Taking too much vitamin A or vitamin D from cod liver oil and other supplements can be harmful. Before taking cod liver oil, tell your health care provider about all of your health conditions, including any food allergies, and any medicines or supplements you may be using.

Uses

What is cod liver oil used for?

Cod liver oil is commonly used to raise the levels of omega-3 fatty acids, vitamin D, and vitamin A in your body. It is also used for other reasons, but its benefits are not well defined.

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

How does cod liver oil work (mechanism of action)?

Cod liver oil is made from the liver of Atlantic cod, a large fish that lives in the very cold ocean waters near Norway and Iceland. Cod liver oil is rich in various nutrients, including omega-3 fatty acids, vitamin A, and vitamin D.

Cod liver oil can contain very large amounts of vitamin A and vitamin D. These vitamins are fat-soluble vitamins that have many important functions in your body. On average, one teaspoon of pure cod liver oil contains 10 mcg (400 IU) of vitamin D and 600 mcg of vitamin A. This is more than half of the entire daily recommended intake of these vitamins for most adults. But each cod liver oil product is different, and a specific product may contain much lower or higher levels of these vitamins. Much lower levels may not be helpful for increasing vitamin A and vitamin D levels in your body. Much higher levels may cause serious side effects.

Cod liver oil also contains docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the omega-3 fatty acids found in fish oil. While cod liver oil is made only from the liver of the fish, fish oil is made from the whole fish. As a result, fish oil contains much larger amounts of DHA and EPA than cod liver oil. In the U.S., most people get enough omega-3 fatty acids from their diet, such as 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.

Cod liver oil naturally contains many nutrients. But the amounts of each nutrient in a specific cod liver oil product may vary. Different amounts of these nutrients may change the effects of cod liver oil on the body. Some cod liver oil dietary supplements are made to contain a specific amount of only some of these nutrients.

How should I store cod liver oil?

You should store cod liver oil according to 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 cod liver oil?

The most common side effects of cod liver 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 cod liver 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 cod liver oil?

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

Severe Allergic Reactions. Cod liver oil may cause allergic reactions, which can be serious. Stop using cod liver 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 that 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 cod liver oil?

Allergies to Ingredients. People who are allergic to any of the following should not use cod liver oil.

  • Cod liver oil
  • Any of the ingredients in the specific product

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

Vitamin A Toxicity. You should not take cod liver oil if you have very high vitamin A (retinol) levels, a condition known as hypervitaminosis A. Your health care provider can order a blood test to check your vitamin A (retinol) levels.

Vitamin D Toxicity. You should not take cod liver oil if you have very high vitamin D levels, a condition known as hypervitaminosis D. Your health care provider can order a blood test to check your vitamin D levels.

What should I know about cod liver oil before using it?

Cod liver 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 using, or use it as recommended by your health care provider.

Keep cod liver oil out of the reach of children.

If you are taking a liquid cod liver oil product, use an accurate measuring device to measure your dose. A household spoon is not an accurate measuring device and may cause you to take the wrong dose. Ask your pharmacist what measuring device to use.

Cod liver oil may contain large amounts of vitamins A and D. You may get these vitamins from several other places, including foods and other vitamins or supplements. Many multivitamins and combination supplement products have these vitamins in them. It is important not to take too much of either vitamin A or vitamin D. Too much of these vitamins can be harmful and can cause toxicity. If you are not sure how much of these vitamins you need, talk to your health care provider.

Cod liver oil naturally contains many different chemicals and nutrients. The amount of each nutrient in a specific cod liver oil product can change for many reasons, including the area where the cod lived, the weather conditions at that time, and the way that the liver 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 cod liver 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 cod liver 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 cod liver oil is right for you.

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

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Kidney or liver problems
  • Smoke cigarettes, now or in the past

Fish Allergy. Cod liver oil supplements are made from cod, which is a type of fish. If you have a fish allergy, you may be at risk of an allergic reaction to cod liver oil. Before taking cod liver oil, tell your health care provider if you are allergic or think that you may be allergic to fish.

Other Medicines and Supplements. Cod liver oil may interact with other medicines and supplements. Before taking cod liver oil, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how cod liver 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 cod liver oil pass into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does cod liver oil interact with foods or drinks?

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

It is unknown if drinking alcohol will affect cod liver oil.

Does cod liver 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.

In particular, make sure that you discuss if you are using any of the following before taking cod liver oil.

  • Acitretin (Soriatane), which is a medicine used to treat psoriasis
  • Bexarotene (Targretin), which is a medicine for a certain form of cancer
  • Orlistat (Alli, Xenical), which is a medicine used for weight loss
  • A statin, such as atorvastatin (Lipitor and others) or rosuvastatin (Crestor), which is a medicine to lower cholesterol
  • A thiazide diuretic, such as chlorthalidone, hydrochlorothiazide, or indapamide, which is a medicine commonly used to lower blood pressure

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

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much cod liver oil?

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

Cod liver oil products may contain many nutrients, including omega-3 fatty acids and some vitamins. Depending on the product, the doses of each nutrient may vary widely. Read the product label closely, and speak with a health care provider about how to take cod liver oil safely. Do not take double or extra doses, even if you miss a dose.