R50.9 Fever, unspecified

The ICD-10-CM code for Fever, unspecified is R50.9 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

18: Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99)

Section

R50-R69: General symptoms and signs (R50-R69)

Category R50

8 codes (6 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to R50.9:

• Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor)
• Pyrexia (of unknown origin)
• Hyperpyrexia
• PUO (pyrexia of unknown origin)
• FUO (fever of unknown origin)
• Elevated, elevation › body temperature (of unknown origin)
• Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › ephemeral (of unknown origin)
• Chill (s) › with fever

Inclusion Terms

• Fever NOS
• Fever of unknown origin [FUO]
• Fever with chills
• Fever with rigors
• Hyperpyrexia NOS
• Persistent fever
• Pyrexia NOS

U.S. Hospital Utilization

• An estimated 148,005 U.S. inpatient stays in 2023 included R50.9 among the documented diagnoses.
• 16,905 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

Signs/symptoms w/o definitive COVID-19: symptom codes (+Z20.822)

(g) Signs and symptoms without definitive diagnosis of COVID- 19 For patients presenting with any signs/symptoms associated with COVID-19 (such as fever, etc.) but a definitive diagnosis has not been established, assign the appropriate code(s) for each of the presenting signs and symptoms such as: • R05.1, Acute cough, or R05.9, Cough, unspecified • R06.02 Shortness of breath • R50.9 Fever, unspecified If a patient with signs/symptoms associated with COVID-19 also has an actual or suspected contact with or exposure to COVID-19, assign Z20.822, Contact with and (suspected) exposure to COVID-19, as an additional code.

Repeated falls vs history of falling

d. Repeated falls Code R29.6, Repeated falls, is for use for encounters when a patient has recently fallen and the reason for the fall is being investigated. Code Z91.81, History of falling, is for use when a patient has fallen in the past and is at risk for future falls. When appropriate, both codes R29.6 and Z91.81 may be assigned together.

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)