Which of the following is NOT a vital sign?

Vital signs are physical measurements that provide essential information about a person's basic body functions and are vital indicators of health status. The core vital signs typically include temperature, respiration rate, heart rate, and blood pressure. These measurements reflect the physiological status of a patient and help in assessing their overall health.

Blood glucose levels, while critical to monitoring and diagnosing conditions such as diabetes, are not classified as a vital sign. They are important indicators of metabolic status and can be vital in specific clinical situations, but they do not fall within the primary category of vital signs used in general assessments. Thus, identifying blood glucose level as the option that is not a vital sign is correct based on the fundamental definitions and classifications of vital signs in healthcare.