Calcium

Background

• Essential for cardiac conduction, muscle contraction, coagulation, and bone metabolism
• Total calcium is ~50% protein-bound; ionized calcium is the physiologically active form

Normal Values

• Total calcium: 8.5-10.5 mg/dL
• Corrected calcium = total Ca + 0.8 x (4.0 - albumin)
• See ionized calcium for direct measurement

Interpretation

• Always correct for albumin or check ionized calcium in hypoalbuminemic patients
• Hypercalcemia (>10.5 mg/dL): malignancy and hyperparathyroidism account for ~90% of cases
  • Symptoms: "stones, bones, groans, and psychiatric overtones"
  • Treat with IV NS (first-line), calcitonin, bisphosphonates
  • ECG: shortened QT interval
• Hypocalcemia (<8.5 mg/dL): most commonly from hypoalbuminemia (check ionized Ca), also renal failure, hypoparathyroidism, vitamin D deficiency
  • Symptoms: perioral/extremity paresthesias, tetany, Chvostek and Trousseau signs, seizures
  • ECG: prolonged QT interval

See Also

• Hypercalcemia
• Hypocalcemia
• Ionized calcium
• BMP