Hypophosphatemia in Emergency Medicine Workup

Updated: Dec 10, 2021
  • Author: Alex Koyfman, MD; Chief Editor: Erik D Schraga, MD  more...
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Laboratory Studies

Serum phosphate level:

  • Serum phosphate or phosphorus normally ranges from 2.5-4.5 mg/dL in adults. Hypophosphatemia is defined as mild (2-2.5 mg/dL), moderate (1-2 mg/dL), or severe (< 1 mg/dL).

  • Since the serum phosphate level may not accurately reflect the level of intracellular phosphate, always correlate serum phosphate levels with clinical findings, especially before embarking upon aggressive replacement therapy.

Abnormalities in serum magnesium, calcium, and potassium levels may occur.

  • Hypomagnesemia often is associated with the shift of phosphate into cells.

  • Hypercalcemia is common in primary hyperparathyroidism.

  • Derangements in serum potassium may occur with certain hypophosphatemia causes, such as DKA and alcoholism.


Other Tests

Urine measurements of phosphate excretion, such as 24-hour excretion or fractional excretion of filtered phosphate, are usually not measured in the emergency department, but these tests may be helpful for admitted patients. These tests provide further evidence of renal versus extrarenal source. [31]

An electrocardiogram should be obtained to assess for arrhythmia.