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v1.0.0
ICD-10 Guide
ICD-10 CodesR50

R50

Fever of other and unknown origin

BILLABLE STATUSYes
IMPLEMENTATION DATEOctober 1, 2015
LAST UPDATED09/11/2025

Code Description

ICD-10 R50 is a billable code used to indicate a diagnosis of fever of other and unknown origin.

Key Diagnostic Point:

Fever of other and unknown origin (FUO) is defined as a fever that persists for more than three weeks without an identified cause after thorough investigation. It is characterized by a body temperature exceeding 38.3°C (101°F) on several occasions. The clinical context of FUO is complex, as it can arise from a variety of underlying conditions, including infections, malignancies, autoimmune diseases, and other inflammatory disorders. Common causes include infections (e.g., tuberculosis, endocarditis), malignancies (e.g., lymphomas), and non-infectious inflammatory conditions (e.g., Still's disease). The diagnostic approach typically involves a detailed history, physical examination, laboratory tests (including blood cultures, imaging studies), and sometimes invasive procedures to identify the underlying cause. Accurate coding requires careful documentation of the fever's duration, associated symptoms, and any diagnostic efforts undertaken to rule out specific conditions.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Variety of potential underlying causes
  • Need for thorough diagnostic workup
  • Differentiation from other fever-related codes
  • Documentation of fever duration and characteristics

Audit Risk Factors

  • Inadequate documentation of fever duration
  • Failure to document diagnostic efforts
  • Misuse of related codes leading to upcoding or downcoding
  • Lack of specificity in clinical notes

Specialty Focus

Medical Specialties

Internal Medicine

Documentation Requirements

Detailed history of fever, associated symptoms, and results of diagnostic tests.

Common Clinical Scenarios

Patients presenting with prolonged fever without clear etiology, requiring extensive workup.

Billing Considerations

Consideration of chronic conditions that may present with FUO.

Emergency Medicine

Documentation Requirements

Acute assessment of fever, vital signs, and initial lab results.

Common Clinical Scenarios

Patients with acute fever presentation, requiring immediate evaluation for serious conditions.

Billing Considerations

Rapid identification of life-threatening causes of fever.

Coding Guidelines

Inclusion Criteria

Use R50 When
  • Follow official ICD
  • CM guidelines for coding symptoms and signs
  • Ensure that the documentation supports the diagnosis of FUO and that all relevant diagnostic efforts are recorded

Exclusion Criteria

Do NOT use R50 When
No specific exclusions found.

Related Codes

Child Codes

7 codes
R50.2
Drug induced fever
R50.8
Other specified fever
R50.81
Fever presenting with conditions classified elsewhere
R50.82
Postprocedural fever
R50.83
Postvaccination fever
R50.84
Febrile nonhemolytic transfusion reaction
R50.9
Fever, unspecified

Related CPT Codes

99223CPT Code

Initial hospital care, high complexity

Clinical Scenario

Used when a patient with FUO is admitted for extensive evaluation.

Documentation Requirements

Detailed history, examination, and medical decision-making.

Specialty Considerations

Internal medicine specialists often manage these cases.

ICD-10 Impact

Diagnostic & Documentation Impact

Enhanced Specificity

ICD-10 Improvements

The transition to ICD-10 has allowed for more specific coding of fever-related conditions, improving the ability to track and analyze FUO cases. This specificity aids in better understanding the epidemiology and management of these patients.

ICD-9 vs ICD-10

The transition to ICD-10 has allowed for more specific coding of fever-related conditions, improving the ability to track and analyze FUO cases. This specificity aids in better understanding the epidemiology and management of these patients.

Reimbursement & Billing Impact

The transition to ICD-10 has allowed for more specific coding of fever-related conditions, improving the ability to track and analyze FUO cases. This specificity aids in better understanding the epidemiology and management of these patients.

Resources

Clinical References

  • •
    ICD-10-CM Official Guidelines for Coding and Reporting

Coding & Billing References

  • •
    ICD-10-CM Official Guidelines for Coding and Reporting

Frequently Asked Questions

What is the duration required to classify a fever as FUO?

A fever must persist for more than three weeks without an identified cause to be classified as fever of unknown origin.