Found this.......
Possible side effects
Fish oil capsules may cause belching, flatulence, bloating, nausea and diarrhoea. Very high doses may result in a slightly fishy body odour. There is some concern that high doses can lead to internal bleeding, but a study of people with heart disease who took 8000 mg of fish oil supplements in addition to aspirin (an anticoagulant) found no increase in the incidence of internal bleeding. Some studies have found that high doses of fish oils worsen blood sugar control in people with diabetes; others have shown no effect. To be safe, diabetics should not take more than 2000 mg of fish oil supplements a day except on medical advice. Individuals with high levels of triglycerides should be careful if they also have high LDL ('bad') cholesterol: therapeutic doses of fish oils can increase LDL. Garlic supplements may be the remedy. One study found that garlic reversed the fish oils' LDL-raising effect. For rheumatoid arthritis and other inflammatory conditions, eating fish is probably not sufficient, and fish-oil supplements are recommended.
Seems like to have these effects you must be prone to them anyway.