Calcium within the periodic table
Classification and external resources
Specialty Endocrinology
ICD-10 E83.5
eMedicine article/241893
Patient UK Hypocalcemia

Hypocalcaemia, also spelled hypocalcemia, is low calcium levels in the blood serum.[1] The normal range is 2.1–2.6 mmol/L (8.8–10.7 mg/dL, 4.3–5.2 mEq/L) with levels less than 2.1 mmol/L defined as hypocalcemia.[2][3][4] Mildly low levels that develop slowly often have no symptoms.[5][6] Otherwise symptoms may include numbness, muscle spasms, seizures, confusion, or cardiac arrest.[2][5]

Common causes include hypoparathyroidism and vitamin D deficiency.[5] Others causes include kidney failure, pancreatitis, calcium channel blocker overdose, rhabdomyolysis, tumor lysis syndrome, and medications such as bisphosphonates.[2] Diagnosis should generally be confirmed with a corrected calcium or ionized calcium level.[5] Specific changes may be seen on an electrocardiogram (ECG).[2]

Initial treatment for severe disease is with intravenous calcium chloride and possibly magnesium sulfate.[2] Other treatments may include vitamin D, magnesium, and calcium supplements. If due to hypoparathyroidism, hydrochlorothiazide, phosphate binders, and a low salt diet may also be recommended.[5] About 18% of people who are in hospital have hypocalcemia.[6]

Signs and symptoms

The neuromuscular symptoms of hypocalcemia are caused by a positive bathmotropic effect due to the decreased interaction of calcium with sodium channels. Since calcium blocks sodium channels and inhibits depolarization of nerve and muscle fibers, diminished calcium lowers the threshold for depolarization.[7] The symptoms can be recalled by the mnemonic "CATS go numb"- Convulsions, Arrhythmias, Tetany and numbness/parasthesias in hands, feet, around mouth and lips.


Hypoparathyroidism is a common cause of hypocalcemia. Calcium is tightly regulated by the parathyroid hormone (PTH). In response to low calcium levels, PTH induces the kidneys to reabsorb calcium, the kidneys to increase production of calcitriol (the active form of vitamin D) thereby increasing intestinal absorption of calcium, and the bones to release calcium. These actions lead to a re-balance in the blood calcium levels. However, in the setting of absent, decreased, or ineffective PTH hormone, the body loses this regulatory function, and hypocalcemia ensues. Hypoparathyroidism is commonly due to surgical destruction of the parathyroid glands via parathyroidectomy or neck dissection for head and neck cancers. Hypoparathyroidism may also be due to autoimmune destruction of the glands.


Physiologically, blood calcium is tightly regulated within a narrow range for proper cellular processes. Calcium in the blood exists in three primary states: bound to proteins (mainly albumin), bound to anions such as phosphate and citrate, and as free (unbound) ionized calcium. Only the ionized calcium is physiologically active. Normal blood calcium level is between 8.5 to 10.5 mg/dL (2.12 to 2.62 mmol/L) and that of ionized calcium is 4.65 to 5.25 mg/dL (1.16 to 1.31 mmol/L).


Because a significant portion of calcium is bound to albumin, any alteration in the level of albumin will affect the level of calcium is measured. A corrected calcium level based on the albumin level is: Corrected calcium (mg/dL) = measured total Ca (mg/dL) + 0.8 * (4.0 - serum albumin [g/dL]). Another way to determine the calcium level is to measure directly the ionized calcium level.


See also


  1. LeMone, Priscilla; Burke, Karen; Dwyer, Trudy; Levett-Jones, Tracy; Moxham, Lorna; Reid-Searl, Kerry (2015). Medical-Surgical Nursing. Pearson Higher Education AU. p. 237. ISBN 9781486014408.
  2. 1 2 3 4 5 Soar, J; Perkins, GD; Abbas, G; Alfonzo, A; Barelli, A; Bierens, JJ; Brugger, H; Deakin, CD; Dunning, J; Georgiou, M; Handley, AJ; Lockey, DJ; Paal, P; Sandroni, C; Thies, KC; Zideman, DA; Nolan, JP (October 2010). "European Resuscitation Council Guidelines for Resuscitation 2010 Section 8. Cardiac arrest in special circumstances: Electrolyte abnormalities, poisoning, drowning, accidental hypothermia, hyperthermia, asthma, anaphylaxis, cardiac surgery, trauma, pregnancy, electrocution.". Resuscitation. 81 (10): 1400–33. PMID 20956045.
  3. Pathy, M.S. John (2006). Principles and practice of geriatric medicine (4. ed. ed.). Chichester [u.a.]: Wiley. p. Appendix. ISBN 9780470090558.
  4. Minisola, S; Pepe, J; Piemonte, S; Cipriani, C (2 June 2015). "The diagnosis and management of hypercalcaemia.". BMJ (Clinical research ed.). 350: h2723. PMID 26037642.
  5. 1 2 3 4 5 Fong, J; Khan, A (February 2012). "Hypocalcemia: updates in diagnosis and management for primary care.". Canadian family physician Medecin de famille canadien. 58 (2): 158–62. PMID 22439169.
  6. 1 2 Cooper, MS; Gittoes, NJ (7 June 2008). "Diagnosis and management of hypocalcaemia.". BMJ (Clinical research ed.). 336 (7656): 1298–302. PMID 18535072.
  7. Armstrong, C.M., Cota, Gabriel. (1999). "Calcium block of Na+ channels and its effect on closing rate". Proceedings of the National Academy of Sciences of the United States of America. 96 (7): 4154–4157. Bibcode:1999PNAS...96.4154A. doi:10.1073/pnas.96.7.4154. PMC 22436Freely accessible. PMID 10097179.
  8. Durlach, J; Bac, P; Durlach, V; Bara, M; Guiet-Bara, A (June 1997). "Neurotic, neuromuscular and autonomic nervous form of magnesium imbalance". Magnesium research. International Society for the Development of Research on Magnesium. 10 (2): 169–95. PMID 9368238.
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