Signs and symptoms
Mild hypokalemia is often without symptoms, although it may cause elevation of blood pressure, and can provoke the development of an abnormal heart rhythm. Severe hypokalemia, with serum potassium concentrations of 2.5–3 meq/L (Nl: 3.5–5.0 meq/L), may cause muscle weakness, myalgia, tremor, and muscle cramps (owing to disturbed function of skeletal muscle), and constipation (from disturbed function of smooth muscle). With more severe hypokalemia, flaccid paralysis and hyporeflexia may result. Reports exist of rhabdomyolysis occurring with profound hypokalemia with serum potassium levels less than 2 meq/L. Respiratory depression from severe impairment of skeletal muscle function is found in some people.It can also cause psychotic as well as other mental symptoms, including hypokalemic sensory overstimulation. Causes
Hypokalemia can result from one or more of these medical conditions:

Inadequate potassium intake
Not eating a diet with enough potassium-containing foods or fasting can cause the gradual onset of hypokalemia. This is a rare cause and may occur in those with anorexia nervosa or those on a ketogenic diet. Gastrointestinal or skin loss
A more common cause is excessive loss of potassium, often associated with heavy fluid losses that flush potassium out of the body. Typically, this is a consequence of diarrhea, excessive perspiration, or losses associated with muscle-crush injury, or surgical procedures. Vomiting can also cause hypokalemia, although not much potassium is lost from the vomitus. Rather, heavy urinary losses of K+ in the setting of post-emetic bicarbonaturia force urinary potassium excretion. (See discussion of alkalosis below.) Other gastrointestinal causes include pancreatic fistulae and the presence of adenoma.
See also
Bartter syndrome
Gitelman syndrome
Hypokalemic acidosis
Potassium deficiency (plant disorder)
Superior mesenteric artery syndrome

References
Further reading
Firth, J (2010). "Disorders of potassium homeostasis". In David A. Warrell; Timothy M. Cox; John D. Firth; Graham S. Ogg (eds.). Oxford Textbook of Medicine. Vol. 1 (5th ed.). Oxford: Oxford University Press. pp. 3831–3845. doi:10.1093/med/9780199204854.003.210202_update_001. ISBN 978-0199204854. Greenlee, M; Wingo, CS; McDonough, AA; Youn, JH; Kone, BC (May 5, 2009). "Narrative review: evolving concepts in potassium homeostasis and hypokalemia" (PDF). Annals of Internal Medicine. 150 (9): 619–25. doi:10.7326/0003-4819-150-9-200905050-00008. PMC 4944758. PMID 19414841. NIHMSID: NIHMS800438. External links
Content of Selected Foods per Common Measure, sorted by nutrient content (Potassium)
List of foods rich in potassium (U. Mass. Med.) National Organization for Rare Disorders: Hypokalemia