Why does my body ache when I have a fever?

Your immune system releases inflammatory chemicals (cytokines like IL-6 and TNF-alpha) that sensitize pain receptors throughout the body. This is actually a beneficial response that encourages rest.

Fever and Body Aches: Flu, Infection, or Something Else?

Important Disclaimer

This guide is for informational purposes and does not replace professional medical advice. If you are experiencing a medical emergency, call 911 or your local emergency services immediately.

Overview

Fever with body aches is your immune system at work. When fighting infection, your body releases cytokines that raise core temperature (fever) and increase inflammation in muscles and joints (aches). This is most commonly caused by viral infections like influenza.

Possible Causes

Influenza

common

The hallmark presentation — sudden high fever with severe generalized body aches, fatigue, and respiratory symptoms.

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COVID-19

common

Systemic viral infection producing fever, muscle pain, and fatigue with variable respiratory involvement.

Bacterial Infection

less-common

UTIs, strep throat, cellulitis, and other bacterial infections can produce fever with localized or generalized aches.

Early Autoimmune Flare

rare

Conditions like lupus or rheumatoid arthritis can present with fever and widespread joint/muscle pain during flares.

When It Is Serious

Seek care for fever above 103°F in adults, fever lasting more than 3 days, fever with rash (especially non-blanching), severe localized pain, or confusion.

When It's Likely Benign

Mild fever (99-101°F) with body aches during known cold/flu season that responds to rest and OTC medication is typically self-limiting.

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Frequently Asked Questions

Related Resources

Fever Guide

Medically Reviewed for Accuracy

Medical Advisory Board

•Last reviewed: March 20, 2026

Content is aligned with established clinical guidelines from authoritative medical institutions, including MedlinePlus (U.S. National Library of Medicine), the CDC, the NIH, and the NHS. All content is reviewed by our medical advisory board for accuracy and safety.