What is the normal serum calcium level?

• A. 7.5-9.5 mg/dL
• B. 8.5-10.5 mg/dL
• C. 9.0-11.0 mg/dL
• D. 8.0-9.0 mg/dL

Answer: (B)

Calcium in the blood is kept within a tight range because it’s essential for nerve signaling, muscle contraction, and blood clotting. The normal total serum calcium level is about 8.5 to 10.5 mg/dL. This range accounts for calcium bound to proteins and the free ionized calcium that actually bioactively works in the body. If albumin is low, total calcium can appear low even with normal ionized calcium, so clinicians may correct for albumin or measure ionized calcium to assess true calcium status. Values below 8.5 mg/dL indicate hypocalcemia; values above 10.5 mg/dL indicate hypercalcemia. Therefore, 8.5-10.5 mg/dL is the normal range.