Your body only requires a specific amount of each vitamin per day. If you consume more than the amount you need, your body will dispose of the excess. However, this is only true of the water soluble vitamins. Fat soluble vitamins cannot be disposed of as easily by your body. If you consume too much of the fat soluble vitamins, your body can suffer adverse affects. Fat soluble vitamins include A, K, and E.
The adverse affects suffered by your body from too much of certain vitamins can be substantial. Elevated doses of vitamin A could cause liver damage. High does of vitamin C could result in diarrhea or stomach bleeding. An excess amount of iron can cause heart and brain damage and potentially lead to heart attack. And too much zinc could impair your immune system.
It is important to compare the recommended daily amounts of each vitamin and mineral to the amount you are receiving in your multivitamin. And it is exceptionally important to compare any additional supplements you take in addition to your multivitamin to make sure the two products are not posing a hazard to your health.