If yourr vitamin doesn’t dissolve, you can bet you will not be able to absorb it.  To test your current vitamins, create a solution of equal parts of vinegar and water and leave the pill in the solution over night.  If it doesn’t dissolve, demand your money back.  Since supplements are not regulated you cannot be sure that the package even contains what the label says.  There was a program started back in 2001 where manufacturers could submit their products to the United States Pharmacopeia for testing.  If you find a USP certification mark on the product you buy, this means that the product meets certain requirements for accuracy in labeling, purity and good manufacturing practices.