Your hormones can get bacteria excited. Also, arthritis can flare up more when you mensturate. If you use birth control: I've found the depo-provera shot to work well, and my cf doc says it's the one patients respond best to. I don't mensturate with it, and this is totally normal, and since it doesn't go through your digestive system, you don't have to worry about it directly interacting w/ other meds or malabsorbtion.Debbie22 yr old w/ cf