Why can't i take pregnancy pills while taking tegretol?

You can: You can still take them, they just may not be as effective. The problem is that tegretol (carbamazepine) causes the hormones in birth control pills to be broken down by the body faster than normal, so you have lower levels of hormones in your blood to prevent pregnancy. If you do take bcps, you would probably need ones with higher amounts of hormones in them. Check with your ob/gyn.