If left untreated, hypokalemia may present as nausea, vomiting that progresses to develop ileus, muscle cramps, rhabdomyolysis and polyuria leading to dehydration. Persistent hypokalemia may lead to ventricular ectopy. Complications of hypokalemia include paralysis, arrhythmias, rhabdomyolysis and ileus. Prognosis of hypokalemia depends upon the underlying condition.

If left untreated, hypokalemia may present as nausea, vomiting that progresses to develop ileus, muscle cramps, rhabdomyolysis and polyuria leading to dehydration. Persistently low serum potassium levels may lead to EKG changes for example, ventricular ectopy (Premature ventricular contractions, ventricular tachycardia, ventricular fibrillation, U waves, prolonged QT interval).

Possible complications include ^[1]:

• Paralysis: In severe cases
• Arrhythmia
• Heart block and cardiac arrest
• Rhabdomyolysis 
• Hepatic encephalopathy in cirrhotic patients
• Constipation

The prognosis depends on underlying condition that cause hypokalemia. Potassium supplements may correct the problem. In severe cases, without proper treatment a severe drop in potassium levels can lead to serious heart rhythm problems that can be fatal.