I take xanax (alprazolam) for anxiety.did fine until yesterday when blood pessure dropped to 80/50, went to er. is it due to xanax (alprazolam) or sth else (have periods, flu)?

All of the above: Antianxiety agents such as Xanax (alprazolam) can potentially lower blood pressure. It can also depend on total amount taken. But your significantly low blood pressure might have also been due to dehydration resulting from symptoms of the flu. Heavy blood loss from menses can potentially also drop pressure, but probably not in and of itself. Hopefully your visit to the ER was of benefit. All the best.