Usually 1 to 2 grams a day is fine along with equal amounts of fish/flax oils to get the proper omega 3 to omega 6 ratios. Most tell you to get omega-6 oils at a 2 to 1 ratio over omega-3 oils but forget that formula as most people are so over fed on omega-6's (all grain products and most baked oils) that Eicosanoids are way out of balanced so just take them both equal if you can....

Note : Evening Primrose is an Omega-6 Fatty Acid.