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Fever in Adults

Published: November 24, 2020

Welcome to this symptom guide about fever. Sorry to hear you have a fever!

This guide is intended for adults who have an abnormally elevated temperature. Although we think of normal body temperature as 98.6 degrees F, body temperature varies -- and so does the definition of fever. Since body temperature rarely climbs above 99.9 degrees without a reason, this guide will consider a fever to be present when the body temperature is 100.0 F (38 degrees C) or higher. While temperatures between 98.6 and 99.9 degrees might be high for you, minor elevations in temperature are less likely to be a true indication of illness and are often within the range of normal variation.

There are many causes of fever. This guide will cover some of the most common, but it is not exhaustive; rarer causes will not be covered.

This guide is not intended to replace a face-to-face meeting with your doctor about your symptoms. Many causes of fever require an in-person examination and testing to diagnose. However, this guide may be particularly helpful while awaiting a visit to your doctor or after your initial evaluation.

Okay. To begin, here's a two-part question:

1. Is your temperature greater than 104 degrees F?

2. Along with fever, do you have any of the following?

- Severe headache

- Shortness of breath

- Lethargy or confusion

- A rapidly spreading rash

- An inability to drink fluids

Yes, one or more of those is true for me.

No, none of those is true for me.

Good. That makes a serious or dangerous cause of fever less likely.

Along with fever, do you have a significant cough?

Yes, I do have a bad cough.

Nope, no cough.

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