Fish Oil

What You Should Know About Fish Oil (Omega-3 Fatty Acids)

By: Joanne Jansen PharmD and Anjanette Dymerski PharmD

Many people consider herbal supplements safe since they are natural. However, even natural things can be bad for you; for example, a bite from a black widow spider is natural and not good. Always discuss any new supplements with your doctor or pharmacist before taking them to make sure they do not interact with your medications or cause worsening of a disease you have.

It is important to remember that natural supplements and vitamins are not regulated by the Food and Drug Administration (FDA). This means that there may be ingredients in the products that are not listed. There is also no guarantee that the ingredients listed on the bottle are accurate.

Fish oil is commonly used for:

  • High triglycerides
  • Heart disease


While fish oil may be beneficial in some people, there are some reasons you may not want to take it. Fish oil may increase your LDL (bad cholesterol) levels significantly. It is generally well tolerated in doses of 4 grams a day or less. Fish oil works similar to the following medications and they should not be taken together:

  • Gemfibrozil (Lopid®)
  • Omega-3-acid ethyl esters (Lovaza®)
  • Fenofibrate (Tricor®)
  • Fenofibric acid (TriLipix®)

Fish oil can cause problems in people with certain diseases.

If you have one of the following, discuss with your doctor or pharmacist whether you should take fish oil:

  • Diabetes
  • Lowered immune function (immunodeficiency)


Other things you should know about fish oil:

  • Tell your doctor you are taking this drug before you have surgery. You may need to stop it two weeks before surgery to prevent bleeding problems.
  • Tell your doctor or pharmacist you are taking this drug before you start any new medications.
  • Fish oil may decrease vitamin E levels.
  • If you have a seafood allergy you should avoid fish oil.
  • Side effects that may occur include fishy breath, nausea, diarrhea, and rash.