Last updated: July 21, 2023

Summarytoggle arrow icon

Hypocalcemia is a state of low serum calcium levels (total Ca2+ < 8.5 mg/dL or ionized Ca2+ < 4.65 mg/dL). Total calcium comprises physiologically-active ionized calcium as well as anion-bound and protein-bound, physiologically-inactive calcium. Calcium plays an important role in various cellular processes in the body, such as stabilizing the resting membrane potential of cells, cell signaling, coagulation, and hormone release. In addition to hormonal control by parathyroid hormone (PTH) and calcitriol, calcium homeostasis is also influenced by serum protein levels and acid-base status, both of which impact the ratio of protein-bound Ca2+ to ionized Ca2+ in the serum. Severity and chronicity of calcium deficiency in addition to the patient's age and comorbidities contribute to the overall clinical presentation of hypocalcemia. Symptoms are variable; the most characteristic features include prolongation of the QT interval and signs of neuromuscular excitation (e.g., tetany, carpopedal spasm, paresthesias). Management consists of calcium supplementation and identifying and treating the underlying cause.

Definitiontoggle arrow icon

  • Hypocalcemia: total serum calcium concentration < 8.5 mg/dL (< 2.12 mmol/L), or ionized (free) calcium concentration < 4.65 mg/dL (< 1.16 mmol/L) [1]
  • Severe hypocalcemia: total serum calcium concentration ≤ 7.5 mg/dL (< 1.9 mmol/L), or ionized (free) calcium concentration < 3.6 mg/dL (< 0.9 mmol/L) [2]
  • Factitious hypocalcemia: an asymptomatic decrease in total calcium with a normal ionized Ca2+ level (typically occurs due to low serum protein levels)

Calcium homeostasis and calcium physiologytoggle arrow icon

Total and ionized calcium concentrations

To remember the effect pH has on PTH, think: pH = PTH and pH = PTH.

The physiological role of calcium [4]

Calcium homeostasis

Calcium homeostasis is a complex process, involving many organs (kidneys, gastrointestinal tract, bones, liver, and skin) and hormones (PTH, calcitonin, vitamin D).

Effect on serum [calcium] Effect on serum [phosphate] Mechanism of action Regulation
Parathyroid hormone

Calcitriol (vitamin D3)
  • Opposes the effects of PTH
  • Inhibits bone resorption, decreasing serum Ca2+

The acronym “PTH” describes the action of parathyroid hormone: P = Phosphate T = Trashing H = Hormone.

To remember that calcitonin keeps the calcium in the bones, think: Calci-bone-in!


Etiologytoggle arrow icon

Types of hypocalcemia Etiology Pathophysiology
Low PTH Hypoparathyroidism
High PTH (secondary hyperparathyroidism) Vitamin D deficiency
Chronic kidney disease
  • PTH resistance


Acute necrotizing pancreatitis (see acute pancreatitis)
  • Calcium soap precipitation in the abdomen

Other Medications
Multiple blood transfusions and hemolysis
Hypomagnesemia (see magnesium)
Osteoblastic metastases
Renal tubular disorders
  • See RTA type 1.
Neonatal hypocalcemia
Hungry bone syndrome

Hypocalcemia is most often due to hypoparathyroidism or vitamin D deficiency (e.g., malabsorption, chronic kidney disease).

Suspect hypocalcemia in the postoperative thyroidectomy patient with new-onset paresthesias and muscle spasms or cramping.


Clinical featurestoggle arrow icon

Manifestations of hypocalcemia are influenced by the severity and chronicity of the hypocalcemia as well as by the patient's age and comorbidities.

Neurological manifestations [1][13][14][15]

Signs of neuromuscular irritability (e.g., paresthesias, spasms and cramps) are the most characteristic features of hypocalcemia.

Cardiovascular manifestations [1][13][14][15]

Manifestations of chronic hypocalcemia [1][13][14][15]

Diagnosticstoggle arrow icon


Acute symptomatic hypocalcemia is a medical emergency that is potentially fatal, diagnostics should not delay treatment.

Laboratory studies [2][13]

Routine studies

Additional studies

Interpretation of laboratory findings in hypocalcemia [1]
PTH level Additional findings Conditions
High PTH

The typical laboratory findings of vitamin D deficiency are calcium, ↓ (or normal) phosphate, and PTH.



  • Recommended in severe/symptomatic cases
  • Possible findings: papilledema [15]

Treatmenttoggle arrow icon

The mainstay of therapy of hypocalcemia consists of calcium supplementation and the treatment of the underlying cause.

Calcium supplementation [2]

Calcium supplementation should be provided based on severity. See “Repletion regimens for hypocalcemia” for more details on calcium supplementation with specific dosages.

IV calcium can trigger life threatening arrhythmias in patients simultaneously receiving cardiac glycosides (digoxin or digitoxin). [1]

Treatment of the underlying condition

Loop diuretics Lose calcium. Discontinue them in hypocalcemia.

Special patient groupstoggle arrow icon

Neonatal hypocalcemia

Overview of neonatal hypocalcemia [17][18][19]
Types Early hypocalcemia Late hypocalcemia
  • < 2–3 days after birth
  • > 2–3 days after birth
  • Most commonly at the beginning of the second week [20]
Etiology Maternal
Clinical features
  • Usually asymptomatic
  • Usually symptomatic
Diagnosis [21]

Preterm infants < 1500 g

Preterm infants ≥ 1500 g and term infants

  • Calcium substitution
  • Treatment of the underlying condition

Referencestoggle arrow icon

  1. Pepe J et al. Diagnosis and management of hypocalcemia. Endocrine. 2020.doi: 10.1007/s12020-020-02324-2 . | Open in Read by QxMD
  2. Turner J, Gittoes N, Selby P, __. SOCIETY FOR ENDOCRINOLOGY ENDOCRINE EMERGENCY GUIDANCE: Emergency management of acute hypocalcaemia in adult patients. Endocrine Connections. 2016; 5 (5): p.G7-G8.doi: 10.1530/ec-16-0056 . | Open in Read by QxMD
  3. Le T, Bhushan V, Chen V, King M. First Aid for the USMLE Step 2 CK. McGraw-Hill Education ; 2015
  4. Goltzman D. Etiology of hypocalcemia in adults. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: January 26, 2016. Accessed: February 10, 2017.
  5. Hyperventilation Syndrome. Updated: July 1, 2016. Accessed: February 10, 2017.
  6. Hypocalcemia: Diagnosis and Treatment. Updated: January 3, 2016. Accessed: July 4, 2019.
  7. Cooper MS, Gittoes NJL. Diagnosis and management of hypocalcaemia. BMJ. 2008; 336 (7656): p.1298-1302.doi: 10.1136/ . | Open in Read by QxMD
  8. Melmed S, Koenig R, Rosen C, Auchus R, Goldfine A. Williams Textbook of Endocrinology. Elsevier ; 2019
  9. Yu ASL, Chertow GM, Skorecki K, Marsden PA, Luyckx V. Brenner and Rector's the Kidney, 2-Volume Set. Elsevier ; 2019
  10. Kennel KA, Drake MT, Hurley DL. Vitamin D Deficiency in Adults: When to Test and How to Treat. Mayo Clinic Proceedings. 2010; 85 (8): p.752-758.doi: 10.4065/mcp.2010.0138 . | Open in Read by QxMD
  11. Jafri L, Khan AH, Azeem S. Ionized calcium measurement in serum and plasma by ion selective electrodes: comparison of measured and calculated parameters.. Indian journal of clinical biochemistry : IJCB. 2014; 29 (3): p.327-32.doi: 10.1007/s12291-013-0360-x . | Open in Read by QxMD
  12. Hall JE. Guyton and Hall Textbook of Medical Physiology. Elsevier ; 2016
  13. Pazirandeh S, Burns DL. Overview of vitamin D. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: January 15, 2016. Accessed: December 14, 2016.
  14. Goldberg D. Calcium, Ionized . In: Staros EB, Calcium, Ionized . New York, NY: WebMD. Updated: December 5, 2014. Accessed: February 10, 2017.
  15. Fuleihan GE-H, Brown EM. Parathyroid hormone secretion and action. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: March 14, 2014. Accessed: February 10, 2017.
  16. Mosekilde L. Vitamin D and the elderly. Clin Endocrinol. 2005; 62 (3): p.265-281.doi: 10.1111/j.1365-2265.2005.02226.x . | Open in Read by QxMD
  17. Tsang RC, Light IJ, Sutherland JM, Kleinman LI. Possible pathogenetic factors in neonatal hypocalcemia of prematurity. J Pediatr. 1973; 82 (3): p.423-429.doi: 10.1016/s0022-3476(73)80115-5 . | Open in Read by QxMD
  18. Kramer MS, Olivier M, McLean FH, Willis DM, Usher RH. Impact of intrauterine growth retardation and body proportionality on fetal and neonatal outcome.. Pediatrics. 1990; 86 (5): p.707-13.
  19. Tsang RC, Chen I, Hayes W, Atkinson W, Atherton H, Edwards N. Neonatal hypocalcemia in infants with birth asphyxia.. J Pediatr. 1974; 84 (3): p.428-33.doi: 10.1016/s0022-3476(74)80733-x . | Open in Read by QxMD
  20. Thomas TC, Smith JM, White PC, Adhikari S. Transient Neonatal Hypocalcemia: Presentation and Outcomes. Pediatrics. 2012; 129 (6): p.e1461-e1467.doi: 10.1542/peds.2011-2659 . | Open in Read by QxMD
  21. Vuralli D. Clinical Approach to Hypocalcemia in Newborn Period and Infancy: Who Should Be Treated?. International Journal of Pediatrics. 2019; 2019: p.1-7.doi: 10.1155/2019/4318075 . | Open in Read by QxMD
  22. Goltzman D. Diagnostic approach to hypocalcemia. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: October 20, 2016. Accessed: February 10, 2017.
  23. Brown EM. Disorders of the calcium-sensing receptor: Familial hypocalciuric hypercalcemia and autosomal dominant hypocalcemia. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: April 12, 2016. Accessed: February 10, 2017.
  24. Goltzman D. Treatment of hypocalcemia. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: April 22, 2015. Accessed: February 10, 2017.
  25. Goltzman D. Clinical manifestations of hypocalcemia. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: April 22, 2015. Accessed: February 10, 2017.
  26. Tao Le, Vikas Bhushan, Deol M, Reyes G. First Aid for the USMLE Step 2 CK, Tenth Edition. McGraw-Hill Education ; 2018
  27. Cecchi. Severe hypocalcemia and life-threatening ventricular arrhytmias: case report and proposal of a diagnostic and therapeutic algorithm. Clinical Cases in Mineral and Bone Metabolism. 2015.doi: 10.11138/ccmbm/2015.12.3.265 . | Open in Read by QxMD
  28. Efremidou et al. Peptic Ulcer Perforation as the First Manifestation of Previously Unknown Primary Hyperparathyroidism. Case Reports in Gastroenterology. 2007; 1 (1): p.21-26.doi: 10.1159/000104224 . | Open in Read by QxMD
  29. Evenepoel P, Viaene L, Meijers B. Calcium balance in chronic kidney disease: walking the tightrope. Kidney Int. 2012; 81 (11): p.1057-1059.doi: 10.1038/ki.2012.33 . | Open in Read by QxMD

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