B27.9 — Infectious mononucleosis, unspecified
Is B27.9 billable?
No — B27.9 is a non-billable header code. B27.9 groups more specific codes and cannot be submitted on a claim. A valid ICD-10-CM code must be reported at the highest level of specificity available in its branch. Select one of the 4 billable codes beneath B27.9.
B27.9 at a glance
| Code | B27.9 |
|---|---|
| Description | Infectious mononucleosis, unspecified |
| Billable | No — header code |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Use additional code — inherited from Chapter 1
Report an additional code alongside B27.9 to fully describe the condition. B27.9 is sequenced first.
- code to identify resistance to antimicrobial drugs (Z16.-)
Excludes2 — not included here — inherited from Chapter 1
The conditions below are not part of B27.9, but a patient may have both at the same time. When documentation supports it, B27.9 and the excluded code may both be reported.
- carrier or suspected carrier of infectious disease (Z22.-)
- certain localized infections - see body system-related chapters
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
- infectious and parasitic diseases specific to the perinatal period (P35-P39)
- influenza and other acute respiratory infections (J00-J22)
What codes fall under B27.9? (4)
How long has B27.9 existed?
B27.9 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.
Which codes are confused with B27.9?
ICD-10-CM declares these codes mutually exclusive with B27.9 — exactly one of each pair can be correct for a given encounter.