> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sonohealth.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Fever in Adults and Children: What's Normal and When to Worry

> What temperature counts as a fever, normal body temperature ranges, and the warning signs in babies, children, and adults that need a doctor or the ER.

A fever is the body's natural response to fighting infection — usually a sign the immune system is doing its job. Knowing what counts as a fever, and which fevers need medical attention, helps you respond calmly and safely.

<Warning>
  Any fever of 100.4°F (38°C) or higher in an infant **under 3 months** is a medical emergency — seek care immediately. For anyone, a fever with confusion, a stiff neck, trouble breathing, a non-fading rash, or a seizure needs emergency care; call 911.
</Warning>

## What temperature is a fever?

In adults and children, a fever is generally a body temperature of **100.4°F (38°C) or higher**. Normal body temperature averages around **98.6°F (37°C)** but varies from person to person and across the day, running a bit lower in the early morning and higher in the late afternoon. A healthy range is roughly 97–99°F (36.1–37.2°C).

## Fever in babies and young children

Children run fevers often, and the number alone isn't the whole story — how the child looks and acts matters more. Contact a doctor if:

* An infant **under 3 months** has any fever of 100.4°F (38°C) — this is urgent.
* A child is **very sleepy or hard to wake**, unusually irritable, or limp.
* There are signs of **dehydration**, trouble breathing, a **stiff neck**, or a rash that doesn't fade under pressure.
* A fever is **high or persistent**, or you're simply worried — trust your instincts.

## Fever in adults

Most adult fevers from common viral illnesses resolve on their own with rest and fluids. Seek care for a fever that is very high, lasts more than a few days, keeps returning, or comes with severe symptoms like difficulty breathing, chest pain, confusion, or a stiff neck.

## When it's an emergency

Go to the ER or call 911 for a very high fever that won't come down (around 104°F/40°C or above), or any fever with confusion, a stiff neck, difficulty breathing, a seizure, a non-fading rash, or signs of severe dehydration.

## Measuring accurately matters

A fever reading is only as good as your technique and method — see [how to take an accurate temperature](/thermometer/how-to-take-accurate-temperature). SonoHealth offers the **ThermoPRO** and **ThermoMax** thermometers for quick home readings; browse them at [SonoHealth.com](https://sonohealth.com/shop/).

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**Related:** [How to Take an Accurate Temperature](/thermometer/how-to-take-accurate-temperature)