Blood Pressure Medication -- DHA may lower blood pressure, so it could make the effects of prescription blood pressure medication stronger.

Anticoagulants (blood thinners) --EPA in fish oil supplements may increase bleeding time, so fish oil could make the effects of these drugs stronger. The same does not appear to be true of DHA alone.

Diabetes medications --Theoretically, fish oil supplements may lower levels of glucose in the blood and could make effects of diabetes drugs stronger. If you have diabetes, talk to your doctor before taking fish oil.

Aspirin --In combination with aspirin, fish oil could be helpful in the treatment of some forms of coronary artery disease. However, this combination may also increase the risk of bleeding. Talk to your doctor to see if this combination is right for you.

Cyclosporine --Omega-3 fatty acids may reduce some of the side effects associated with cyclosporine therapy, which is often used to reduce rejection in transplant recipients. Talk to your doctor before adding any new herbs or supplements to your existing medication regimen.