Hypokalemia in Emergency Medicine Workup

Updated: Oct 11, 2018
  • Author: David Garth, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Laboratory Studies

Laboratory studies include the following:

  • Serum potassium level < 3.5 mEq/L (3.5 mmol/L) [11]

  • BUN and creatinine level

  • Glucose, calcium, and/or phosphorus level if coexistent electrolyte disturbances are suspected.

  • Magnesium levels are unreliable and typically do not change management, since patients with hypokalemia almost always have coincident hypomagnesemia and should be treated empirically.

  • Consider digoxin level if the patient is on a digitalis preparation; hypokalemia can potentiate digitalis-induced arrhythmias.

  • Consider arterial blood gas (ABG): Alkalosis can cause potassium to shift from extracellular to intracellular.


Imaging Studies

CT scan of the adrenal glands is indicated if mineralocorticoid excess is evident (rarely needed emergently).


Other Tests


  • T-wave flattening or inverted T waves

  • Prominent U wave that appears as QT prolongation (see the image below)

    Prominent U waves after T waves in hypokalemia. Prominent U waves after T waves in hypokalemia.
  • ST-segment depression

  • Ventricular arrhythmias (eg, premature ventricular contractions [PVCs], torsade de pointes, ventricular fibrillation) [10]

  • Atrial arrhythmias (eg, premature atrial contractions [PACs], atrial fibrillation)

Thyroid screening studies - Thyroid-stimulating hormone (TSH), free T3, and free T4 in patients with tachycardia, especially Asian patients [12]