Body temperature serves as a vital indicator of health, helping detect potential illnesses. Since the COVID-19 pandemic, regular home monitoring has become commonplace. However, readings vary by measurement site. Health experts recommend these proven methods to accurately assess if you have a fever.
You can measure temperature rectally, axillarily (under the armpit), orally (under the tongue), in the ear, or on the forehead. Signs like a warm forehead, chills, or glassy eyes warrant a check. Rectal measurement remains the gold standard for reliability, using electronic thermometers for axillary, oral, and rectal sites, while ear readings employ infrared devices.
At rest, normal human body temperature ranges between 36.8°C and 37.3°C. Rectally, a reading of 37.8°C to 38°C indicates fever. Temperatures are typically lower in the morning than evening. Notably, high fevers (39.5°C to 40°C) don't always signal severe illness in adults or children—focus on accompanying symptoms and overall impact. This baseline is known as basal temperature.
For accurate basal or normal body temperature in good health, measure upon waking—after 12 hours without food or exercise. Values vary individually. Take morning readings before rising, consistently at the same time. In premenopausal women, it fluctuates with the menstrual cycle: below 37°C early on, rising post-ovulation through the luteal phase, then dropping around day 28.
Infrared forehead thermometers offer contactless, quick scans via temporal artery radiation, but they're less precise than invasive methods. Crystal strip thermometers are even less reliable and unsuitable for infants or young children.
Axillary readings are less accurate than rectal—add 0.5°C to the result. Ensure the armpit is dry, position the electronic thermometer perpendicular in the hollow, lower your arm firmly against your chest to seal out air, and await the reading.
Mercury thermometers were phased out in 1996 due to breakage risks. Use digital electronic models today. Lubricate the tip with petroleum jelly or cool water, insert up to 2 cm into the rectum. For infants, limit to 3 times daily to avoid irritation. It beeps in seconds for a precise result—the most trusted method.
Suitable from age 5, place the electronic thermometer under the tongue in contact. Close your mouth without biting, breathe through your nose, and wait for the beep. Add 0.5°C to the display. Avoid hot/cold drinks or smoking beforehand for accuracy.
Infrared ear thermometers work from age 2, ideally adults. Use a disposable cover, pull the ear upward, insert into the canal, and note the beep. Repeat 2-3 times, taking the highest reliable value.
Disinfect electronic thermometers after each use: wash the tip with soapy water, rinse, dry thoroughly, or use an alcohol swab. Store in its case—never submerge fully to prevent damage.
For adults, rectal or oral routes provide top accuracy. Opt for rectal in infants and young children.
