Serum potassium level is diagnostic
Normal = 3.5-5meq/L
Severe<unk>  = <2.5meq/L
Always check magnesium
Na+/K+ ATPase pump requires Mg to function, therefore low Mg can lead to refractory hypoK
Suggestive ECG findings:
ST segment depression
U wave (V4-V6)
QT prolongation
Premature ventricular contraction
Normal = 3.5-5meq/L
Severe<unk>  = <2.5meq/L
Na+/K+ ATPase pump requires Mg to function, therefore low Mg can lead to refractory hypoK
ST segment depression
U wave (V4-V6)
QT prolongation
Premature ventricular contraction
Hypokalemia
Alkalosis 
Hyponatremia
Insulin
Hypernatremia
Beta agonists
Hyperkalemia
Hypokalemic periodic paralysis