Last Literature Review: May 2018 Last Update:

Hypocalcemia can occur either acutely or chronically in hospitalized patients and outpatients. Testing includes calcium, albumin, phosphate, magnesium, creatinine, 25-hydroxy vitamin D, and parathyroid hormone (PTH).


Indications for Testing

  • Neurologic signs
    • Perioral numbness or other paresthesias
    • Muscle spasms/cramps
    • Neuromuscular irritability
  • Thyroid or parathyroid resection or other neck surgery, irradiation to neck
  • Chronic kidney disease
  • Prolongation of QT interval on electrocardiogram (ECG)
  • Malnutrition or malabsorption

Laboratory Testing

  • Initial testing
    • Serum calcium and albumin 
      • Corrected calcium = measured total calcium + 0.8 (4.0 - serum albumin)
    • Phosphate
    • Magnesium
    • Creatinine
  • If calcium is low, consider repeat testing with ionized calcium
    • Ionized calcium needs no correction for hypoalbuminemia but should be corrected for pH
  • If hypocalcemia is confirmed, order intact PTH
    • Elevated PTH, normal or high phosphate, normal magnesium, high creatinine: consider renal failure/pseudohypoparathyroidism
    • Elevated PTH, normal or low phosphate, normal magnesium, normal creatinine: consider vitamin D testing
    • Low PTH, normal or high phosphate, normal creatinine, low or normal magnesium: consider hypoparathyroidism or hypomagnesemia
    • Normal PTH, normal or low phosphate, normal creatinine, normal magnesium, low albumin: consider hypoalbuminemia (pseudohypocalcemia)


  • Serum calcium, phosphate, and creatinine: measure weekly during initial therapy, then monthly
  • Once stabilized on therapy, measure values one to two times/year

ARUP Laboratory Tests

Related Tests


Additional Resources

Medical Experts



Lauren N. Pearson, DO, MPH
Associate Professor of Pathology (Clinical), University of Utah
Laboratory Director for ARUP at University of Utah Health and Huntsman Cancer Institute
Laboratory Director, South Jordan and Sugarhouse Health Center Clinical Laboratories