Fever Thermometer F.A.Q.

Tips – Fever Thermometers

1. What is a Fever?

A fever is a temporary increase in the body’s temperature in response to a disease or virus. Fevers are an important part of the body’s defense against infections. Most bacteria and viruses that cause infections in people thrive best at 37.0 C (98.6 F). Many infants and children develop high fevers with mild viral illnesses. Although a fever signals that a battle might be going on in the body, the fever is fighting FOR, not against that person.

2. What is Normal body temperature by measure site?

1. - Ear: 35.4 – 37.4°C / 95.7 – 99.3°F

2. - Axillary / Underarm: 34.7 – 37.3°C / 94.5 – 99.1°F

3. - Oral: 35.5 – 37.5°C / 95.9 – 99.5°F

4. - Rectal: 36.6 – 38.0°C / 97.9 – 100.4°F

*Readings from different measuring sites should not be compared as the normal body temperature varies by measuring site and time of day, being highest in the evening and lowest about one hour before waking up

3. What are the recommended thermometers to use, by age?

*Axillary/Underarm measurements are ideal for general screening, but not accurate enough for tracking a fever in young children.

4. How do I properly take a temperature using a Regular Stick Thermometer by measuring site?

1. 1. Orally: If you're taking your child's temperature orally, place the tip of the thermometer under the tongue, towards the back of the mouth, and leave it there as directed by the manufacturer. The child needs to breathe through their nose.  Don't let your child bite on the thermometer or talk. The child must be old enough to cooperate, therefore this method is often used in children aged 4 to 5 years or older. Digital thermometers may beep when they are ready to be read. Wait 30 minutes before taking the temperature if a child has consumed hot or cold foods or drinks. 

   2. Rectally: If you're taking your child's temperature rectally, place him or her belly-down across your lap. Coat the tip of the thermometer with petroleum jelly and insert it half an inch into the rectum. Stop if you feel any resistance. Never let go of the thermometer. This method often works best with infants. 

   3. Axillary: An axillary (Underarm) temperature is a safe way to take the temperature of toddlers and children under 4 years of age. Place the thermometer in the child's underarm and hold the arm against the child's body so that the tip of the thermometer is covered.  Axillary measurements, however, are not as accurate as rectal measurements and should not be used for tracking a fever.

5. What is an Ear Temperature?

An ear temperature, also known as a tympanic membrane temperature, is the medical term for “Eardrum” temperature. This is a gentle and easy way of measuring your body temperature inside of your ear. It only takes a few seconds to check an ear temperature, making it an easier way for children (over the age of 2) because it’s so quick.

6. Are Ear Temperatures Accurate?

BIOS Ear Thermometers take a reading in 1 second and have excellent instrument accuracy +/- 0.2C. However, they require proper measurement techniques for reliable body temperatures.  

There is a common misunderstanding that ear thermometers are inaccurate as the readings often vary because users frequently aren’t aiming at the proper target.  It is very important when using an ear thermometer to point the probe directly at the eardrum.

An ear thermometer measures infrared energy radiated from the eardrum and the surrounding tissue. This energy is collected through the lens and converted to a temperature value. Measurements should be directly from the eardrum or tympanic membrane.

*Readings from the ear canal are not a good representation of core body temperature.

7. How do I properly take a temperature using an Ear Thermometer?

• Before measurements, remain in a stable environment and avoid exercise and bathing for at least 30 minutes.
• Hold your child’s head so it does not move, or tell the person not to move their head.
• Straighten the ear canal by gently pulling the middle of the ear back and up and placing the probe firmly into the ear canal. Doing this helps to straighten out the ear canal and makes it easier to insert the probe tip.
• Always insert the thermometer in the same ear with the same direction and depth.  It is recommended that you measure the temperature 3 times in the same ear. If the 3 measurements are different, select the highest one. (Allow 30 seconds between each measurement). 
• Earwax in the ear canal may cause a lower temperature reading; therefore it is important to ensure the patient’s ear canal is clean.

*It is not recommended to use infrared ear thermometers on infants due to the ear canal not yet being fully developed.  If you are taking an ear measurement, be careful that the opening of the ear is large enough to accept the thermometer’s probe.  If the probe is too large, it will measure the temperatures of the ear canal and not the eardrum.

8. Is a forehead thermometer accurate?

Forehead thermometers, particularly electronic ones, are accurate for detecting fevers. It is essential to follow the manufacturer's instructions carefully and ensure proper usage to obtain the most accurate readings. To obtain an accurate reading with a forehead thermometer, aim the probe at the center of the forehead with a distance of no more than 5 cm. If the forehead area is covered with hair, sweat, or dirt, please remove this obstruction before using the thermometer.

9. Why is my temperature different on each side of my forehead?

Temperature readings may vary on different sides of the forehead. Taking multiple temperature readings over the same area in rapid succession can cool the skin, leading to inconsistent results. Additionally, head coverings like hair or hats can prevent heat from dissipating evenly, causing inaccurately high readings on the covered side of the forehead. To get the most accurate temperature measurement, allow a short time between readings and take measurements from different sides of the forehead.

10. When should I contact my physician?

Follow the guidelines below to help decide when to call your doctor, but it's important to call your doctor whenever you feel that your child needs help or if you have any questions:

1. Under one month old: Call your doctor right away if your baby's temperature goes over 38.5°C (101.3°F) rectally, even if he or she doesn't seem sick. Your doctor may want to see your baby and may want to admit them to the hospital to find out what's causing the fever. Babies this young can get very sick, very quickly. Call your doctor if your baby has any of the warning signs or symptoms listed below, even if they aren’t running a fever.

2. One to three months old: Call your doctor if your baby has a temperature of 38.5°C (101.4°F) even if your baby doesn't seem sick, or a temperature of 38.0°C (100.4°F) that has lasted more than 24 hours. Call your doctor if your baby has any of the warning signs or symptoms listed below.

3. Three months to two years: If your child has a fever of 38.6°C (101.4°F), watch how they act. Call the doctor if the fever rises or lasts for more than three days, or if your child has any of the warning signs or symptoms listed below. If the temperature is 39.0°C (103°F), call your doctor even if your child seems to feel fine.

4. Over two years old: If your child has a fever of 38.6°C (101.4°F), watch how he or she acts. Call the doctor if the fever rises or lasts more than three days or if your child has any of the warning signs or symptoms listed below:

Warning Signs & Symptoms:

Changes in behavior 
Severe headache 
Constant vomiting or diarrhea 
Skin rashes 
Dry mouth 
Sore throat that doesn't improve 
Earache that doesn't improve or pulling at ears 
Stiff neck 
Fever persisting over several days 
Stomach pain 
High-pitched crying 
Swelling on the soft spot on the head 
Irritable 
Unresponsive or limp 
Not hungry 
Wheezing or problems breathing 
Pale 
Whimpering 
Seizures 
Sore or swollen joints