ICD-10-CM 2027
ICD-10 code for pyrexia
From the official ICD-10-CM alphabetic index entry “Pyrexia (of unknown origin)”. Page updated September 29, 2026.
About coding pyrexia
The ICD-10-CM code for pyrexia is R50.9 (Fever, unspecified). The official index lists 7 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on R50.9.
Within R50, choose R50.9 (Fever, unspecified) only when documentation doesn't support a more specific option: drug induced fever (R50.2) and other specified fever (R50.8).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 864 (Fever and Inflammatory Conditions, relative weight 0.8551), in MDC 18 (Infectious and Parasitic Diseases, Systemic or Unspecified Sites), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific pyrexia codes (official index)
- atmospheric T67.01 — Heatstroke and sunstroke
- during labor NEC O75.2 — Pyrexia during labor, not elsewhere classified
- heat T67.01 — Heatstroke and sunstroke
- newborn P81.9 — Disturbance of temperature regulation of newborn, unspecified
- environmentally-induced P81.0 — Environmental hyperthermia of newborn
- persistent R50.9 — Fever, unspecified
- puerperal O86.4 — Pyrexia of unknown origin following delivery
Common questions about pyrexia ICD-10 codes
What is the ICD-10 code for pyrexia?
- R50.9 — Fever, unspecified. More specific codes apply when the documentation supports them: T67.01, O75.2, T67.01, P81.9 and others below.
What is the ICD-10 code for atmospheric pyrexia?
- T67.01 — Heatstroke and sunstroke (header code; choose a more specific subcode).
What is the ICD-10 code for heat pyrexia?
- T67.01 — Heatstroke and sunstroke (header code; choose a more specific subcode).
What is the ICD-10 code for newborn pyrexia?
- P81.9 — Disturbance of temperature regulation of newborn, unspecified.
What is the ICD-10 code for persistent pyrexia?
- R50.9 — Fever, unspecified.
What is the ICD-10 code for puerperal pyrexia?
- O86.4 — Pyrexia of unknown origin following delivery.
Is R50.9 billable?
- Yes. R50.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can R50.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict R50.9 as a principal diagnosis.
Is R50.9 a CC or MCC?
- No. R50.9 is neither a CC nor an MCC under MS-DRG v44.0.