Most vitamins are water-soluble. When the body doesn't need them, it will lead to a decline in absorption rate, which is self-regulating and not easy to be poisoned.
A few of them are fat-soluble vitamins such as A, E and K. Excessive intake will lead to poisoning.
Both of them are micro-supplements, which can be eaten for four weeks and stopped for two weeks.
This will basically not be poisoned.
So, it is basically the same. Food supplement.