If you are currently being treated with any of the following medications, you should not use omega-3 fatty acid supplements without first talking to your healthcare provider.

Blood-thinning Medications
Omega-3 fatty acids may increase the blood-thinning effects of aspirin or warfarin. While the combination of aspirin and omega-3 fatty acids may actually be helpful under certain circumstances (such as heart disease), they should only be taken together under the guidance and supervision of your healthcare provider.

Cyclosporine

Taking omega-3 fatty acids during cyclosporine therapy may reduce toxic side effects (such as high blood pressure and kidney damage) associated with this medication in transplant patients.

Etretinate and Topical Steroids
The addition of omega-3 fatty acids (specifically EPA) to a drug regimen of etretinate and topical corticosteroids may improve symptoms of psoriasis.

Cholesterol-lowering Medications
Following certain nutritional guidelines, including increasing the amount of omega-3 fatty acids in your diet and reducing the omega-6 to omega-3 ratio, may allow a group of cholesterol lowering medications known as "statins" (such as atorvastatin, lovastatin, and simvastatin) to work more effectively.

Nonsteroidal Anti-inflammatory Drugs (NSAIDs)
In an animal study, treatment with omega-3 fatty acids reduced the risk of ulcers from nonsteroidal anti-inflammatory drugs (NSAIDs). More research is needed to evaluate whether omega-3 fatty acids would have the same effects in people.