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Serum Calcium

Aka: Serum Calcium, Corrected Serum Calcium, Ionized Calcium, Free Calcium

Physiology
1. Parathyroid Hormone (PTH) modulates Serum Calcium
  1. PTH rises in response to low calcium
  2. PTH falls in response to high calcium
2. Vitamin D modulates calcium gastrointestinal absorption
3. Total body calcium distribution
  1. Skeleton: 98%
  2. Circulating: 2%
    1. Free or ionized Serum Calcium (active): 50%
    2. Albumin-bound Serum Calcium (inactive): 50%
Normal (normal range varies by individual labs)
1. Serum Calcium: 8 to 10 mg/dl
2. Ionized (free) Calcium: 4 to 5.6 mg/dl
Correcting Serum Calcium for Albumin
1. No correction needed for Ionized Calcium
2. Calculation 1
  1. Serum Calcium / (0.6 + (Total Protein/8.5))
3. Calculation 2
  1. Calcium + ((Normal Albumin - Serum Albumin) x 0.8)
  2. Where normal albumin is often 4.0
Abnormal
1. Hypercalcemia
  1. Mild: Serum Calcium 10.5 to 12 mg/dl
  2. Moderate: Serum Calcium 12 to 14 mg/dl
  3. Critical: Serum Calcium 14 mg/dl or higher
2. Hypocalcemia
  1. Serum Calcium under 8.0 mg/dl

Family Practice Notebook

Patients should address specific medical concerns with their physicians.

Although access to this page is not restricted, the information found here is intended for use by medical providers.

This page was written by Scott Moses, MD, last revised on 10/21/2007 and last published on 5/14/2013.

This is one of 5887 pages in the Family Practice Notebook