Comment by dimitrov

To add another data point: 4,000 IU (two Kirkland capsules) daily keeps my Vitamin D levels at the high end of the reference range. I also take six Kirkland fish oil capsules which happens to hit the 1,500 mg DHA+EPA target suggested in the article.

Honestly, Costco supplements are hard to beat since they're both USP certified and are usually the cheapest.