Illinois CNA State Practice Exam 2026 - Free CNA Practice Questions and Study Guide

When using a rectal glass thermometer, it is essential to follow the appropriate duration for accurate readings. Leaving the thermometer in the rectum for approximately 3 minutes ensures that it can adequately register a stable and accurate core body temperature.

The reason for this time frame is that rectal thermometers are designed to measure the internal body temperature, which can fluctuate based on various factors, including the environment and recent activity. The 3-minute duration allows for the thermometer to reach equilibrium with the body’s internal temperature, providing a reliable reading. This duration balances safety and accuracy, as too short of a time may result in an inaccurate measurement, while too long could be uncomfortable for the patient.