Hi V.,
Dodge anything sold at Walmart, Sam's, GNC or a CVS type store. These are considered "drug-store" grade and are actually dangerous. They "absorb," NOT, by a process called sulfonate or gluconate. These type of vitamin/mineral actually causes free radical activity, which is what causes diseases. There are some better vitamins sold at pharmaceutical grade health stores (usually absorb through a process called chelate) but there are some that are much much better out there.
Just so you'll know. If you are getting ANY type of nutrient you will feel some extra energy but that doesn't necessarily mean they are good for you. I take the only one on the market that is actually guaranteed to absorb. I buy it online. The company also offer a 90 day, money back guarantee if you don't feel better. They are also the cheapest cost of the pharmaceutical grade vitamins. Bobbi McCaughey, who is the only woman in medical history to deliver seven HEALTHY babies was on these and still takes them.
Let me know and I can send you some specific information outlining why they are better than the others. I'd like to help.
M.