Which value range is commonly cited as the normal total serum calcium range?

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

Answer: (C)

Calcium homeostasis and what total serum calcium measures are the key ideas. Total calcium reflects both the free, ionized portion and the calcium bound to proteins (primarily albumin), and its level is tightly regulated by hormones and vitamin D. The normal total calcium range most commonly cited is about 8.5 to 10.5 mg/dL. This window aligns with standard reference intervals used in many labs and exams, capturing values that indicate normal calcium status. Values below 8.5 mg/dL point toward hypocalcemia, which can cause symptoms like tingling, muscle cramping, or cardiac irritability. Values above 10.5 mg/dL point toward hypercalcemia, which can lead to fatigue, constipation, kidney stones, or altered mental status. Therefore, the range 8.5-10.5 mg/dL is the best fit for a normal total serum calcium value, while ranges that fall below or exceed this interval indicate abnormal calcium status.