Definition

By Mayo Clinic Staff

Fatigue is a common symptom. Almost everyone feels it during short-term illness. Fortunately, fatigue usually goes away when the illness is over.

But sometimes fatigue doesn't go away. It doesn't get better with rest. And the cause might be unclear.

Fatigue reduces energy, the ability to do things and the ability to focus. Ongoing fatigue affects quality of life and state of mind.

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Feb. 20, 2026

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