The potential side effects of taking omega 3-6-9 fish oil include a fishy aftertaste, burping, bloating and nausea, according to WebMD. More serious side effects to this medication are easy bleeding and bruising of the skin.
Some people who take 3-6-9 fish oil experience a severe allergic reaction, notes WebMD. Symptoms of this allergic reaction include itching and swelling of the face, tongue and throat. More symptoms include rash, trouble breathing and extreme dizziness. If these symptoms occur, the patient must immediately seek medical attention for the effects of the drug. Other side effects occasionally occur and should be reported along with any unusual symptoms or changes in health to a doctor.