Hypocalcemia

Medical Experts

Contributor

Pearson

Lauren N. Pearson, DO, MPH

Associate Professor of Pathology (Clinical), University of Utah

Chief Medical Officer, ARUP at University of Utah Health

Contributor

Straseski

Joely A. Straseski, PhD, MS, MT(ASCP), DABCC, FAACC

Professor of Pathology (Clinical), University of Utah

Head of Clinical Operations for Clinical Chemistry, Toxicology, and Biochemical Genetics; Medical Director, Endocrinology; Co-Director, Automated Core Laboratory, ARUP Laboratories

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).

Diagnosis

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 vitamin D 25(OH): vitamin D deficiency confirmed
- 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)

Monitoring

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