DHA-500 Fish Oil, Double Strength - 90 SoftgelsNOW DHA 500 has twice the DHA (500 mg per softgel) as in our regular strength product (250 mg per softgel). This fish oil concentrate is manufactured under strict quality control standards. It is tested for potentially harmful levels of contaminants such as PCBs, dioxins, mercury and other heavy metals. Those who experience nausea or reflux from other fish oils should find this enteric coated, odor controlled softgel easier to tolerate. From the FDA: