Which tests are performed in the evaluation of suspected hypokalemia (low potassium level)?

Updated: Dec 06, 2018
  • Author: Eleanor Lederer, MD, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Depending on history, physical examination findings, clinical impressions, and urine potassium results, the following tests may be appropriate. They should not be first-line tests, however, unless the clinical index of suspicion for the disorder is high:

  • Drug screen in urine and/or serum for diuretics, amphetamines, and other sympathomimetic stimulants

  • Serum renin, aldosterone, and cortisol

  • 24-hour urine aldosterone, cortisol, sodium, and potassium

  • Pituitary imaging to evaluate for Cushing syndrome

  • Adrenal imaging to evaluate for adenoma

  • Evaluation for renal artery stenosis

  • Enzyme assays for 17-beta hydroxylase deficiency

  • Thyroid function studies in patients with tachycardia, especially Asians [2]

  • Serum anion gap (eg, to detect toluene toxicity)

Simultaneous serum insulin and C-peptide tests can detect covert insulin use, which may occur in Münchhausen or Münchhausen-by-proxy syndrome. An elevated serum insulin level without an appropriately elevated C-peptide level suggests exogenous insulin administration.

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