OK, I don't know how many of you may or may not be on birth control. I am, actually for health reasons. Even if you count on it for only health reasons, you need to keep in mind there are some natural herbs that can interfere with birth control. It can possibly nullify what you're taking it for, but most of all, you could end up pregnant. Guess where some of these herbs are? Diet pills! If you're on birth control, you'll want to read the label. A couple years back, I had a pregnancy scare when I was taking something with chasteberry while on birth control. Thankfully, I was not pregnant.
There are several sites that can confirm this if you dig, but that's the most comprehensive list I've seen.
Black and Blue Cohosh
Fennel (food quantity is too small to matter)
Hops (same disclaimer for beer as fennel)
St. John’s Wort