2027 ICD-10-CM Diagnosis Code B27Infectious mononucleosis

ICD-10-CM Codes›A00–B99›B25-B34›B27

ICD-10-CM B27
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

B27 is a non-billable ICD-10-CM category code for infectious mononucleosis, so it cannot be submitted on claims. Use a more specific code from this category instead, such as B27.00, B27.01, B27.02, and B27.09.

Code Identity

ICD-10-CM Code
B27
Billable Status
No — Non-Billable Category
Code Describes
Infectious mononucleosis
Short Description
Infectious mononucleosis
Same as the full description in the CMS dataset.
Chapter
B25-B34
Other viral diseases

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionB25-B34Other viral diseases
CategoryB27Infectious mononucleosis
This CodeB27Infectious mononucleosis

Specific Coding for Infectious mononucleosisOverview

Non-specific codes like B27 require more characters. Use one of these billable codes instead:

  • B27.0 for Gammaherpesviral mononucleosis

  • Use B27.00 for Gammaherpesviral mononucleosis without complication

  • Use B27.01 for Gammaherpesviral mononucleosis with polyneuropathy

  • Use B27.02 for Gammaherpesviral mononucleosis with meningitis

  • Use B27.09 for Gammaherpesviral mononucleosis with other complications

  • B27.1 for Cytomegaloviral mononucleosis

  • Use B27.10 for Cytomegaloviral mononucleosis without complications

  • Use B27.11 for Cytomegaloviral mononucleosis with polyneuropathy

  • Use B27.12 for Cytomegaloviral mononucleosis with meningitis

  • Use B27.19 for Cytomegaloviral mononucleosis with other complication

  • B27.8 for Other infectious mononucleosis

  • Use B27.80 for Other infectious mononucleosis without complication

  • Use B27.81 for Other infectious mononucleosis with polyneuropathy

  • Use B27.82 for Other infectious mononucleosis with meningitis

  • Use B27.89 for Other infectious mononucleosis with other complication

  • B27.9 for Infectious mononucleosis, unspecified

  • Use B27.90 for Infectious mononucleosis, unspecified without complication

  • Use B27.91 for Infectious mononucleosis, unspecified with polyneuropathy

  • Use B27.92 for Infectious mononucleosis, unspecified with meningitis

  • Use B27.99 for Infectious mononucleosis, unspecified with other complication

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to B27: its own notes plus those printed at Chapter 1. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

On B27 itself
  • glandular fever
  • monocytic angina
  • Pfeiffer's disease
From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • diseases generally recognized as communicable or transmissible

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • 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)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • code to identify resistance to antimicrobial drugs (Z16.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name B27, its category, or a range that includes it.

Applicable To 1

These notes mention B27.

  • O98.5 Other viral diseases complicating pregnancy, childbirth and the puerperium
    Conditions in A80-B09, B25-B34, R87.81-, R87.82- names B25-B34, which includes this code

Excludes1 3

These codes carry an Excludes1 note naming B27: they are not reported together with it, unless the two conditions are unrelated.

  • D72.821 Monocytosis (symptomatic)
    infectious mononucleosis (B27.-)
  • G02 Meningitis in other infectious and parasitic diseases classified elsewhere
    infectious mononucleosis complicated by meningitis (B27.- with fifth character 2)
  • J02.8 Acute pharyngitis due to other specified organisms
    acute pharyngitis due to infectious mononucleosis (B27.-)

Clinical InformationClinical

  • Infectious Mononucleosis

    a common, acute infection usually caused by the epstein-barr virus (herpesvirus 4, human). there is an increase in mononuclear white blood cells and other atypical lymphocytes, generalized lymphadenopathy, splenomegaly, and occasionally hepatomegaly with hepatitis.

Patient EducationClinical

Infectious Mononucleosis

Infectious mononucleosis (mono) is a disease caused by viruses.The most common cause is the Epstein-Barr virus (EBV). Mono is contagious, which means it can spread from person to person. It is common among teenagers and young adults, especially college students.

The full article covers:

  • What is infectious mononucleosis (mono)?
  • What causes infectious mononucleosis (mono)?
  • What are the symptoms of infectious mononucleosis (mono)?
  • How is infectious mononucleosis (mono) diagnosed?
  • What are the treatments for infectious mononucleosis (mono)?
  • Can infectious mononucleosis (mono) be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About B27Overview

What is the ICD-10 code for infectious mononucleosis?

B27 is the ICD-10-CM category for infectious mononucleosis, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is B27 (Infectious mononucleosis) a billable code?

No. This is a category header that groups the codes for infectious mononucleosis, and headers cannot be submitted on claims. Claims for infectious mononucleosis need a more specific code from this category, such as B27.00, B27.01, and B27.02.