Hypocalcemia most often occurs either acutely or chronically in hospitalized patients and outpatients. Initial testing includes calcium, albumin, phosphate, magnesium, and creatinine.

  • Diagnosis
  • Algorithms
  • Monitoring
  • Background
  • Lab Tests
  • References
  • Related Topics
  • Videos

Indications for Testing

  • Neuromuscular irritability combined with neurologic signs and symptoms
  • Appropriate clinical setting for hypocalcemia (eg, thyroid or previous parathyroid removal)

Laboratory Testing

  • Initial testing
    • Serum calcium and albumin [corrected calcium = measured total calcium +0.8 (4.0-serum albumin)], or use ionized calcium
    • Phosphate
    • Magnesium
    • Creatinine
  • If calcium 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 parathyroid hormone (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)

Differential Diagnosis

  • See etiology section in Clinical Background
  • Serum calcium, phosphate, and creatinine – measure weekly during initial therapy, then monthly
  • Once stabilized on therapy, measure values 1-2 times/year


  • Prevalence – occurs in 12-80% of critically ill patients


  • Acute hypocalcemia – intensive care unit patients (acute pancreatitissepsis)
  • Hypoparathyroidism
    • Acquired
      • Surgical removal of parathyroids (eg, head and neck surgery)
      • Radiation-induced parathyroid destruction
      • Metastatic infiltration of glands (rare)
      • Other infiltrative disorders (eg, hemochromatosis)
    • Autoimmune
      • Associated with polyglandular syndrome 1
    • Pseudohypoparathyroidism
      • Resistance to parathyroid hormone (eg, chronic renal failure)
    • Genetic syndromes
  • Vitamin D deficiency
  • Magnesium deficiency
  • Medications
    • Chemotherapy drugs
    • Anticonvulsants
    • Foscarnet
    • Histamine – 2 receptor blockers
    • Proton pump inhibitors
    • Bisphosphonates


  • Serum calcium concentration kept within a narrow physiologic range
  • Control of calcium by parathyroid hormone, vitamin D (1,25), calcium, and phosphate
  • Calcium is bound to albumin
    • Low levels may reflect hypoalbuminemia, not level of ionized calcium

Clinical Presentation

  • Symptom severity related to rate of change and absolute calcium levels
    • Most patients with mild hypocalcemia are asymptomatic
  • Acute
    • Neuromuscular – tetany, paresthesias, muscle spasms (Chvostek and Trousseau signs), perioral numbness
    • Neuropsychiatric – anxiety, hallucinations, confusion, irritability
    • Cardiovascular – bradycardia, ventricular arrhythmias, congestive heart failure, cardiac collapse
    • Pulmonary – laryngeal stridor, bronchospasm
  • Chronic
    • Neuropsychiatric – cognitive deficits, extrapyramidal symptoms
    • Dermatologic – dermatitis, dry skin, brittle nails
    • Dental – enamel hypoplasia
    • Ophthalmologic – cataracts
Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory.

Calcium, Serum or Plasma 0020027
Method: Quantitative Spectrophotometry

Albumin, Serum or Plasma by Spectrophotometry 0020030
Method: Quantitative Spectrophotometry

Calcium, Ionized, Serum 0020135
Method: Ion-Selective Electrode/pH Electrode

Phosphorus, Inorganic, Plasma or Serum 0020028
Method: Quantitative Spectrophotometry

Parathyroid Hormone, Intact 0070346
Method: Quantitative Electrochemiluminescent Immunoassay

Magnesium, Plasma or Serum 0020039
Method: Quantitative Spectrophotometry

Vitamin D, 25-Hydroxy 0080379
Method: Quantitative Chemiluminescent Immunoassay

General References

Baird GS. Ionized calcium. Clin Chim Acta. 2011; 412(9-10): 696-701. PubMed

Bosworth M, Mouw D, Skolnik DC, Hoekzema G. Clinical inquiries: what is the best workup for hypocalcemia? J Fam Pract. 2008; 57(10): 677-9. PubMed

Chang WW, Radin B, McCurdy MT. Calcium, magnesium, and phosphate abnormalities in the emergency department. Emerg Med Clin North Am. 2014; 32(2): 349-66. PubMed

Cooper MS, Gittoes NJ. Diagnosis and management of hypocalcaemia. BMJ. 2008; 336(7656): 1298-302. PubMed

De Sanctis V, Soliman A, Fiscina B. Hypoparathyroidism: from diagnosis to treatment. Curr Opin Endocrinol Diabetes Obes. 2012; 19(6): 435-42. PubMed

Fong J, Khan A. Hypocalcemia: updates in diagnosis and management for primary care. Can Fam Physician. 2012; 58(2): 158-62. PubMed

Michels TC, Kelly KM. Parathyroid disorders. Am Fam Physician. 2013; 88(4): 249-57. PubMed

Medical Reviewers

Last Update: October 2017