Yes. You can overdose on any vitamin supplement. Just like prescribed medication, supplements are refined, concentrated substances that can cause serious damage to the body if taken in excess. Remember, there is no substitute for a healthy diet. Nutritional supplements are unnescssary for most people.
HUGE question. There is no way that this can be answered in 400 characters or less. Please ask about specific supplements so that we can respond. Recommend inquiring about each supplement in separate submissions.