There are many fish oil dietary supplements on the market.[14] There appears to be little difference in effect between dietary supplement and prescription forms of omega-3 fatty acids as to ability to lower triglycerides, but the ethyl ester products work less well when taken on an empty stomach or with a low-fat meal.[2] The ingredients of dietary supplements are not as carefully controlled as prescription products and have not been tested in clinical trials as such drugs have.[15] Prescription omega-3 products are more concentrated, requiring fewer softgels for the same daily dose.[14]