What is the critical range for calcium?

• A. 4-9 mg/dL
• B. 6-13 mg/dL
• C. 8-14 mg/dL
• D. 5-11 mg/dL

Answer: (B)

Calcium is a tightly controlled number in the blood, and labs separate values into ordinary versus critical that require urgent action. The thresholds commonly used to define the critical window for total calcium are about 6 mg/dL at the lower end and 13 mg/dL at the upper end. Values outside this band signal a potential life-threatening imbalance, so they trigger immediate notification and clinical intervention. That’s why 6–13 mg/dL is used as the critical range—the band that guides when urgent steps are needed to address dangerous hypo- or hypercalcemia.