What kind are you taking? I am taking DuetDHA. I take them both at night and they don't make me sick or anything. They did boost my energy for sure and I am not nearly as tired as I was before.
FYI Kristin, if the vitamins get too expensive for you, I was told that any over-the-counter "PreNatal" vitamin would work just as well as the prescribed. And makes sure you eat your green leafy stuff.