How long should a thermometer be placed under the tongue for an accurate oral temperature reading?

• A. 1-2 minutes
• B. 3-4 minutes
• C. 5-6 minutes
• D. 7-8 minutes

Answer: (B)

Accurate oral temperature reading relies on allowing the thermometer to equilibrate with the mouth’s temperature. The sensor needs several minutes in contact with the sublingual tissues to reach a stable value that reflects core oral temperature, not the initial mouth temperature. About 3–4 minutes is sufficient for most thermometers to stabilize, giving a reliable reading. If you wait only 1–2 minutes, the measurement is often affected by the temperature of the lips, breath, or recent intake and can be inaccurate. Waiting much longer (5–8 minutes) isn’t typically more accurate and can be uncomfortable or subject to drift from saliva flow or device behavior. For best results, keep the thermometer in the sublingual pocket with lips closed and avoid recent eating or drinking until after the reading is taken.