Arthritis Home > Cod Liver Oil Side Effects

A fishy aftertaste, heartburn, and nausea are some of the more bothersome side effects of cod liver oil. These side effects can also potentially be serious and may require medical attention. Some of the serious side effects to watch out for include unusual bruising or bleeding, blood in the stool, and signs of an allergic reaction.

Does Cod Liver Oil Cause Side Effects?

Even though it is a "natural" product, cod liver oil is not free of side effects. For most people, these side effects are merely bothersome. However, cod liver oil can sometimes cause serious side effects as well, especially when taken at higher dosages, which is often necessary in order to obtain the benefits of cod liver oil.

Bothersome Side Effects of Cod Liver Oil

Many people who are taking cod liver oil may experience gastrointestinal side effects, such as:
  • A fishy aftertaste
  • Bad breath
  • Heartburn or indigestion
  • Nausea
  • Loose stools.
Taking cod liver oil with meals and starting with a low cod liver oil dosage and slowing increasing it may help decrease these gastrointestinal side effects.

Serious Cod Liver Oil Side Effects

Some side effects with cod liver oil should be reported to your healthcare provider, as they may indicate that you should stop taking it. These include but are not limited to:
  • Any unusual bruising or bleeding (cod liver oil can increase the risk of bleeding)
  • Signs of gastrointestinal bleeding, such as:
    • Black, tarry stools
    • Bright red blood in the stool
    • Vomiting blood
  • Signs of a hemorrhagic stroke (bleeding in the brain), such as:
    • Vision or speech changes
    • Weakness or numbness in an arm or leg
    • Severe headache
  • Signs of an allergic reaction, such as:
    • An unexplained rash
    • Hives
    • Itching
    • Unexplained swelling
    • Wheezing
    • Difficulty breathing or swallowing.
Because cod liver oil contains quite a bit of vitamins D and A, it is also possible that side effects can occur due to toxicities from either of these vitamins. There is some concern that long-term use of cod liver oil could increase the risk of skin cancer. If cod liver oil is accidentally inhaled into the lungs, it can cause a form of pneumonia.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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