> ## 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.

# When to Worry About a Fever in Adults

> What counts as a fever in adults, when a fever is a medical emergency, the warning signs that matter more than the number, and how to track a fever at home.

A fever is the body's normal response to infection, and in healthy adults it's usually not dangerous on its own. Still, some fevers — and some accompanying symptoms — do warrant prompt care. Here's how to tell the difference.

<Warning>
  Seek emergency care for a fever with a stiff neck, severe headache, confusion, trouble breathing, chest pain, a spreading rash, persistent vomiting, or seizures. When in doubt about severe symptoms, call 911.
</Warning>

## What counts as a fever in adults?

A temperature of about **100.4°F (38°C) or higher** is generally considered a fever. Normal body temperature varies by person, time of day, and measurement site, so a number slightly above your own baseline isn't necessarily a fever — see [what's a normal body temperature](/thermometer/fever-guide).

## When is an adult fever an emergency?

The number matters less than the **company it keeps**. Get urgent care for a fever paired with a stiff neck, confusion, severe headache, difficulty breathing, chest pain, a new rash that doesn't fade under pressure, or persistent vomiting. A very high fever (around 103°F/39.4°C or above) that won't come down, or any fever lasting more than a few days, also deserves a call.

## Does a higher fever mean a worse illness?

Not reliably. The height of a fever doesn't track neatly with how serious an illness is — a mild virus can spike a high number, and a serious infection sometimes causes only a modest rise. How you feel and your other symptoms are better guides than the thermometer alone.

## Who should be more cautious?

Older adults, people who are pregnant, and those who are immunocompromised or managing a chronic illness should have a **lower threshold** for seeking care, since fevers can signal more in these groups — and older adults sometimes run a blunted fever response. When unsure, check with a clinician.

## How do I track a fever at home?

Use a consistent method and time, and log the readings along with symptoms. A fast, reliable thermometer such as SonoHealth's **ThermoPRO** makes repeat checks easy, and a clear record helps your doctor judge the trend. Rest, fluids, and over-the-counter fever reducers (used as directed) help comfort while you monitor.

***

**Related:** [Fever Guide](/thermometer/fever-guide) · [How to Take an Accurate Temperature](/thermometer/how-to-take-accurate-temperature) · [Low Body Temperature](/thermometer/low-body-temperature) · [Fever in Children Guide](/thermometer/fever-in-children-guide)