The ICD-10-CM code for mononucleosis is B27.90 — Infectious mononucleosis, unspecified without complication. This is the code the Alphabetic Index gives for mononucleosis with no further qualifier, valid for FY2027 (October 1, 2026 – September 30, 2027).
BillableUnspecified
B27.90 is billable but unspecified. If the documentation names a type, site or cause, one of the more specific codes below is likely expected.
Which mononucleosis code should you use?
The Alphabetic Index lists 16 codes under Mononucleosis, infectious. Which one applies depends on the qualifier documented in the record — the type, site, cause, or associated condition. Find the qualifier below, then verify the code in the Tabular List before using it.
Other infectious mononucleosis with polyneuropathy
Index terms and codes are reproduced from the official ICD-10-CM FY2027 release. The Alphabetic Index is a finding aid — a code must always be verified in the Tabular List before it is reported. Data sources