Ratio of EPA and DHA Fatty Acids

• Compare the amount of EPA (Eicosapentaenoic acid) and DHA (Docasahexaenoic acid) in your fish oil supplements. These are the two most important Omega 3 fatty acids. It is important to get the highest possible ratio of EPA to DHA. The standard ratio is 18/12, but there are some supplements that offer a ratio as high as 40/20, which is preferable, as recommended by the Physicians for Optimal Heart and Brain Health, according to Energy First.
  
  

Cleanness

• If possible, make sure that any toxins, especially mercury, have been cleaned out of your fish oil supplement by molecular distillation, or that the fish that were the source of the fish oil came from a clean, noncontaminated area of the ocean.
  
  

Freshness

• Your fish oil supplement should also be fresh. There's an easy test for this: If it makes you burp, it is not fresh, and you should switch to another brand, according to Women's Health Questions.