what causes low potassium in a 38 yr old female?

Answer 1

Vomiting and diarrhea are common causes of low potassium. Certain medications can also cause it (especially diuretics). There are other medical conditions that can cause it, and this article lists quite a few:

http://en.wikipedia.org/wiki/Hypokalemia

Answer 2

EXCESSIVE OR EXTRA FLUID LOSS IS ONE REASON

AND NOT TAKING IN POTASSIUM LIKE ORANGE JUICE--BANANA'S AND SUCH.

MULTI VIT'S/MINERALS TABS DON'T ALWAYS GET ABSORBED.