What Temperature Is Considered a Fever in Children? A Pediatrician Explains
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In general, a temperature of 100.4°F (38°C) or higher is considered a fever in children. But the number is only part of the story.
Your child's age, how the temperature was measured, how your child looks and acts, breathing, hydration and other symptoms are often more important than whether the thermometer reads 101°F, 102°F or 103°F.
One important exception: a rectal temperature of 100.4°F (38°C) or higher in a baby younger than 3 months warrants prompt medical guidance.
- 100.4°F (38°C) or higher is generally considered a fever.
- Normal body temperature is not always exactly 98.6°F.
- Body temperature naturally changes during the day.
- The method used to measure temperature matters.
- The height of a fever does not reliably tell you how serious an illness is.
- How your child looks, acts, drinks and breathes matters greatly.
- Babies younger than 3 months require special attention when fever is present.
Is 100°F a Fever in a Child?
Usually, no. A temperature around 100°F by itself does not necessarily meet the standard definition of fever.
Body temperature naturally varies from child to child and throughout the day. Physical activity, warm clothing, a warm environment and the method used to take the temperature can also affect the reading.
In general, pediatricians consider 100.4°F (38°C) or higher to be a fever.
Is 98.6°F Really the Normal Temperature?
Many parents grew up learning that 98.6°F is the normal human body temperature.
It is better to think of normal temperature as a range rather than one exact number.
A healthy child's temperature may be somewhat lower or higher than 98.6°F depending on the time of day, activity level and how the temperature is measured.
A number slightly above 98.6°F does not automatically mean that your child is sick.
Treat the child, not just the thermometer.
The temperature gives us useful information, but I am often much more interested in whether a child is drinking, interacting, breathing comfortably and becoming more like themselves when the fever comes down.
Does the Way I Take the Temperature Matter?
Yes.
Temperature readings can differ depending on where and how they are measured.
Common methods include:
- Rectal temperature
- Oral temperature
- Forehead or temporal artery temperature
- Ear or tympanic temperature
- Axillary temperature taken under the arm
No thermometer is useful if it is being used incorrectly, so follow the manufacturer's directions for your particular device.
Which Temperature Method Is Most Accurate?
The best method depends partly on the child's age.
Rectal temperature is generally the most accurate method for confirming fever in very young infants.
As children become older, other methods such as forehead, ear or oral temperatures can be useful when performed correctly with an appropriate thermometer.
Underarm temperatures are convenient but can be less precise.
If the reading does not fit with how your child looks or you are unsure whether a fever is truly present, repeat the measurement using an age-appropriate method.
Is 99°F a Fever?
Generally, no.
A temperature in the 99°F range can occur normally, particularly later in the day or after activity.
You do not need to treat a child simply because the thermometer reads 99°F.
Is 100.4°F a Fever?
Yes. A temperature of 100.4°F (38°C) reaches the generally accepted fever threshold.
What you do next depends on the child's age, symptoms and overall condition.
If your baby is younger than 3 months and has a rectal temperature of 100.4°F (38°C) or higher, contact your pediatrician or healthcare professional promptly.
Do not wait for the temperature to reach 102°F or 103°F. Young infants require a different approach to fever than older babies and children.
Is 101°F a High Fever?
A temperature of 101°F is certainly a fever, but in an older infant or child it is not generally considered unusually high.
The number alone does not determine whether your child has a serious illness.
A child with a temperature of 101°F who is difficult to wake, struggling to breathe or refusing fluids can concern me much more than a child with a temperature of 103°F who is drinking and interacting comfortably.
Is 102°F a High Fever?
A temperature of 102°F is a common fever during childhood infections.
Many viral illnesses can produce temperatures in this range.
Again, pay attention to your child's behavior and other symptoms rather than judging the illness entirely by the thermometer.
Is 103°F Dangerous?
Seeing 103°F on the thermometer understandably makes parents nervous.
But fever in this range is common with many childhood infections and is not automatically dangerous.
Look at the entire clinical picture: age, breathing, hydration, alertness, pain, rash, duration of illness and other symptoms.
What About a Fever of 104°F?
A temperature of 104°F deserves careful attention, but the number still does not tell us the diagnosis by itself.
Contact your pediatrician for guidance, particularly if the fever is persistent or your child has concerning symptoms.
Seek urgent medical attention if your child appears seriously ill, regardless of the exact temperature.
Does a Higher Fever Mean a More Serious Infection?
Not necessarily.
Some routine viral infections can cause high temperatures, while some serious illnesses may cause only a modest fever.
This is why pediatricians do not diagnose the seriousness of an illness simply by looking at the highest temperature.
The child's age, examination and associated symptoms provide much more information.
When your child has a fever, pay attention to:
- How well your child is drinking
- Urination and wet diapers
- Breathing
- Alertness and interaction
- Comfort level
- Vomiting or diarrhea
- Rash
- Pain
- How long the fever has lasted
- Whether your child improves when the fever decreases
Should I Treat Every Fever?
No.
Fever is part of the body's immune response to infection. The goal of fever medicine is generally to make an uncomfortable child feel better, not to force the temperature back to 98.6°F.
An older child who has a mild fever but is drinking, playing and comfortable may not need medication simply because the thermometer displays an elevated number.
Medication decisions should be based on your child's age, weight, comfort and your healthcare professional's recommendations.
When your child is uncomfortable from a fever, Dr. G's QuickDose™ provides simple, weight-based pediatric dosing guidance for Tylenol® (acetaminophen) and Motrin® (ibuprofen).
Visit the QuickDose page to learn how it works and choose the option that's right for you—including using QuickDose free on the Pediatric Parent Guide website.
QuickDose is an educational dosing guide and does not replace your child's pediatrician or other qualified healthcare professional. Always follow the safety guidance provided with the tool.
When Should I Call My Pediatrician?
Contact your pediatrician or healthcare professional when:
- Your baby is younger than 3 months and has a rectal temperature of 100.4°F (38°C) or higher.
- Your child's fever is persistent or repeatedly returning.
- Your child is drinking poorly or showing signs of dehydration.
- Your child has significant pain.
- Your child has a new or concerning rash.
- Your child is unusually sleepy, irritable or not acting normally.
- You are concerned about your child's breathing.
- You are uncertain about the temperature reading or how to manage the fever.
- Your instincts tell you that your child needs to be evaluated.
When Is Fever an Emergency?
Seek emergency medical care if your child:
- Is struggling to breathe or stops breathing
- Has blue, gray or markedly pale lips or skin
- Is extremely difficult to wake or is unresponsive
- Has a seizure
- Has a stiff neck with severe illness or other concerning symptoms
- Appears severely ill or is rapidly worsening
- Has any other symptoms that make you believe your child may be experiencing a medical emergency
There is no magic fever number that tells you everything you need to know about your child.
The thermometer tells us that a fever exists. Your child's age, behavior and other symptoms help tell us what that fever may mean.
Common Questions About Fever Temperatures
Is 99°F a fever in a child?
Usually not. Body temperature normally fluctuates, and readings in the 99°F range can occur in healthy children.
Is 100°F considered a fever?
A temperature of exactly 100°F generally remains below the standard fever threshold of 100.4°F (38°C).
Is 100.4°F considered a fever?
Yes. A temperature of 100.4°F (38°C) or higher is generally considered a fever.
Is 103°F dangerous for a child?
Not automatically. Many common infections can cause a temperature of 103°F. Your child's age, appearance, hydration, breathing and other symptoms are important in determining how concerning the illness is.
Does fever cause brain damage?
Fevers caused by ordinary infections are regulated by the body's temperature-control system and are different from dangerous overheating or hyperthermia. Parents should focus on the child's overall condition and seek medical care for concerning symptoms.
The Bottom Line
A temperature of 100.4°F (38°C) or higher is generally considered a fever in children.
But the number on the thermometer should never be interpreted in isolation.
Your child's age, how the temperature was measured, how your child looks and behaves, breathing, hydration and other symptoms all help determine what the fever means.
For most older babies and children, the height of the fever alone does not determine how serious an illness is.
The major exception is a young infant: a baby younger than 3 months with a rectal temperature of 100.4°F (38°C) or higher needs prompt medical guidance.
Related Fever Resources
Have another question about fever? Explore the complete Fever in Children Parent Guide for practical pediatric guidance about fever medicines, warning signs, temperature measurement and when to seek medical care.
References
- American Academy of Pediatrics, HealthyChildren.org. Fever: When to Call the Pediatrician.
- American Academy of Pediatrics, HealthyChildren.org. How to Take Your Child's Temperature.
- Sullivan JE, Farrar HC; American Academy of Pediatrics. Fever and Antipyretic Use in Children. Pediatrics. 2011;127(3):580–587.
- Pantell RH, Roberts KB, Adams WG, et al. Evaluation and Management of Well-Appearing Febrile Infants 8 to 60 Days Old. Pediatrics. 2021;148(2):e2021052228.
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