Vitamin B complex and vitamin C are water soluble, and your kidney should just flush them out. There is growing evidence that excessive doses can result in considerable harm. Too much vitamin A can cause liver failure. The risk is so high that pregnant women are often warned not to eat liver, a very rich source of it. Studies in the U.S. have reported that too much of the vitamin causes fetal abnormalities.
Vitamin E can reduce clotting, but in large doses can lead to internal bleeding.
Vitamin K can stop bleeding, but large doses can cause a potentially fatal thrombosis. There are even growing fears that vitamin C can cause problems. In large amounts it is thought not to be an antioxidant but a pro-oxidant, the opposite of its intended effect. Collins often has to deal with the effects of excessive dosages. There are also risks that it could conceal symptoms of something serious.