What is the threshold alert value for high plasma sodium?

• A. 160 mmol/L
• B. 150 mmol/L
• C. 170 mmol/L
• D. 180 mmol/L

Answer: (A)

Threshold alert value is the point at which a laboratory result is abnormal enough to demand immediate attention and clinical action. For high plasma sodium, many laboratories set this alert at about 160 mmol/L. This level is above the normal range (roughly 135–145 mmol/L) and above mild hypernatremia, signaling a need for rapid clinical assessment to prevent potential neurologic complications from rapid shifts in brain water balance. Values around 150 mmol/L indicate hypernatremia but are typically not treated as urgent alerts, while much higher values (170–180 mmol/L) represent more severe, critical states. Therefore, 160 mmol/L is the common threshold used to trigger an alert.