Fever of Unknown Origin

Overview

Fever of unknown origin (FUO) is a specific term for a persistent fever (classically beyond three weeks) for which a thorough initial evaluation — history, examination and basic tests — has not revealed a cause. It is not the same as a prolonged fever that has not yet been investigated. FUO requires a deeper, staged work-up and often specialist collaboration. This page is distinct from Prolonged Fever, which applies before that initial evaluation is complete.

What FUO includes

• Infections — tuberculosis, deep abscesses, certain uncommon infections.
• Non-infectious inflammatory conditions — including autoimmune disease.
• Certain cancers — especially lymphoma.
• Drug-related fever.
• A small fraction remain unexplained even after full evaluation.

Evaluation

The work-up is staged and guided by clues: a careful repeated history and examination, extended blood tests, imaging (CT/MRI), targeted cultures, tuberculosis and autoimmune screening, and sometimes a biopsy. The aim is to reach a diagnosis while avoiding unnecessary or repeated broad treatments.

Management

Treatment targets the cause once identified. Symptomatic fever relief is provided during the work-up. Empirical (trial) treatment is used only in carefully selected situations, not as a substitute for diagnosis. Specialist referral is often part of the process.

Warning signs — seek urgent care

• Very high fever with confusion, drowsiness or low blood pressure.
• Rapid weight loss, drenching night sweats or enlarged lymph nodes.
• Fever with bleeding, breathlessness or new severe pain.

How we help

Dr. Nayak conducts a staged evaluation for fever of unknown origin, coordinates imaging and specialist referral, and treats the cause once found — avoiding repeated empirical treatments. Consultations are available in-clinic in Bhubaneswar and over teleconsultation.

Related conditions and patient concerns

• Prolonged Fever
• Recurrent Fever
• Fever
• Abnormal Test Results
• Fatigue, Weakness & General Symptoms