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Hypocalcemia is a topic covered in the 5-Minute Emergency Consult.

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  • Hypocalcemia is defined as a total plasma calcium level <8.7 mg/dL:
    • Ionized calcium may be normal and, therefore, have no clinical manifestations.
  • Normal total serum calcium concentrations are 8.7–10.5 mg/dL.


  • Incidence in the general population is 0.6%.
  • Mechanism:
    • From either increased loss of calcium from the circulation or decreased entry into the circulation
    • Intravascular calcium circulates in 3 forms:
      • Bound to proteins (mainly albumin): 45–50%
      • Bound to complexing ions (citrate, phosphate, carbonate): 5–10%
      • Ionized (free) calcium (physiologically active form): 45–50%
    • Serum levels of calcium are primarily controlled by 3 hormones:
      • Parathyroid hormone (PTH)
      • Decrease in calcium levels leads to an increase in PTH secretion (increasing bone resorption, renal absorption, intestinal absorption, urinary phosphate excretion).
    • Vitamin D (1,25-dihydroxyvitamin D):
      • Decrease in calcium level activates vitamin D (increasing bone resorption and intestinal absorption).
    • Calcitonin:
      • Causes a direct inhibition of bone resorption with increased calcium levels
  • Hypoalbuminemia—the most common cause:
    • Each 1 g/dL decrease in serum albumin decreases protein-bound serum calcium by 0.8 mg/dL.
    • Ionized (free) calcium levels do not change.

Pediatric Considerations
  • Children have higher values of normal calcium (9.2–11 mg/dL).
  • Neonatal hypocalcemia: Total serum calcium concentrations <7.5 mg/dL or serum-ionized calcium levels <4 mg/dL
  • Symptoms of hypocalcemia in infancy:
    • Hyperactivity, jitteriness
    • Tachypnea
    • Apneic spells with cyanosis
    • Vomiting

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Rosen, Peter, et al., editors. "Hypocalcemia." 5-Minute Emergency Consult, 5th ed., Lippincott Williams & Wilkins, 2016. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307399/all/Hypocalcemia.
Hypocalcemia. In: Rosen P, Shayne P, Barkin AZ, et al, eds. 5-Minute Emergency Consult. 5th ed. Lippincott Williams & Wilkins; 2016. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307399/all/Hypocalcemia. Accessed April 25, 2019.
Hypocalcemia. (2016). In Rosen, P., Shayne, P., Barkin, A. Z., Wolfe, R. E., Hayden, S. R., Barkin, R. M., & Schaider, J. J. (Eds.), 5-Minute Emergency Consult. Available from https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307399/all/Hypocalcemia
Hypocalcemia [Internet]. In: Rosen P, Shayne P, Barkin AZ, Wolfe RE, Hayden SR, Barkin RM, Schaider JJ, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2016. [cited 2019 April 25]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307399/all/Hypocalcemia.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Hypocalcemia ID - 307399 ED - Rosen,Peter, ED - Shayne,Philip, ED - Barkin,Adam Z, ED - Wolfe,Richard E, ED - Hayden,Stephen R, ED - Barkin,Roger M, ED - Schaider,Jeffrey J, BT - 5-Minute Emergency Consult UR - https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307399/all/Hypocalcemia PB - Lippincott Williams & Wilkins ET - 5 DB - Emergency Central DP - Unbound Medicine ER -