I dont know how about Lithium but I know that Lamictal decreases the effects of my birth control (it's the case in general)... Im purely assuming its the same for your medicine. Since it is a "standard" medicine for the treatment of bipolar, I highly doubt it cant be mixed with birth control. Just be extra safe if you're active and I'd make your doctor aware that you are taking birth control as well so if nothing else they have it on your records for future reference