[b:75d61f01ff]Not all vitamin and minerals are tested or verified for their contents. [/b:75d61f01ff]The FDA does not test supplements until someone complains or someone becomes ill or has an adverse reaction. [b:75d61f01ff]It's Buyers Beware[/b:75d61f01ff], this is one of the reasons USP was established. They are a non-profit, 3rd party verifier of pharmacueticals as well as supplements.
If you vitamin or mineral hasn't been tested by USP, it's probably still OK. However, I really like the idea of someone volunteering their products for testing as well as their manufacturing facility.
Here's the link to their site. They have a product and manufacture list. Some vitamin manufacturers bottle for several stores brands.