You can take Crestor and fish oil together. They are both good sources of the healthy fat and they won't cause any problems if taken together. No interactions have been found or reported between Crestor and fish oil. The supplement, Crestor is used to lower cholesterol to healthier levels. Fish oils, on the other hand have omega-3 fatty acids which is useful in lowering the level of Triglycerides in the blood. They have no effect on each other if taken together at the same time. They would work just the same together as they would if taken separately. It is safe for you to take Crestor and fish oil together.