 Always buy directly from the brand, an authorized reseller, or Amazon itself. Get your supplements delivered? Take a minute to see if they're part of the Amazon Shopping or Transparency App program. If the product's brand participates, you can just scan the product's transparency code with your phone. This quick check tells you if what you've got is the real deal or a fake. Better yet, you can buy most supplements directly from the real brand's website. That's what I do.