What is the normal serum calcium range (total)?

• A. 6.0-8.0 mg/dL
• B. Approximately 8.5-10.5 mg/dL
• C. 10.5-12.5 mg/dL
• D. 9.0-11.0 mg/dL

Answer: (B)

The main idea here is understanding the normal total serum calcium level. Total calcium reflects both the calcium bound to proteins (mostly albumin) and the portion that is free (ionized) and biologically active. The standard reference range for adults is about 8.5 to 10.5 mg/dL. This range is used because it typically supports essential functions like muscle contraction, nerve signaling, and cardiac activity, while staying within limits that prevent symptoms of deficiency or excess.

Albumin levels can affect the total calcium reading. If albumin is low, total calcium may fall even when the ionized calcium is normal, so clinicians sometimes adjust calcium values or measure ionized calcium for accuracy. Values within 8.5–10.5 mg/dL are considered normal; lower values suggest hypocalcemia and higher values suggest hypercalcemia.