I33.9 — Acute and subacute endocarditis, unspecified
Is I33.9 billable?
Yes, but I33.9 is an unspecified code. I33.9 is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, I33.9 is an unspecified or catch-all code. Payers apply additional scrutiny to unspecified codes and many deny them when the medical record supports a more specific option, so check the documentation before selecting I33.9 — the more specific alternatives are listed below.
More specific alternatives
I33.9 at a glance
| Code | I33.9 |
|---|---|
| Description | Acute and subacute endocarditis, unspecified |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does I33.9 group to?
I33.9 sits in MDC 05 and helps define the logic of 3 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 288Acute and Subacute Endocarditis with MCCmedical
- 289Acute and Subacute Endocarditis with CCmedical
- 290Acute and Subacute Endocarditis without CC/MCCmedical
As a secondary diagnosis, I33.9 is a major complication or comorbidity (MCC), which can move a stay into a higher-paying DRG.
How is I33.9 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to I33.9. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Endocarditis › acute or subacute (chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
- Endocarditis › toxic (chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
- Endocarditis › aortic › acute or subacute (chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
- Endocarditis › pulmonary › acute or subacute (chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
- Endocarditis › mitral › nonrheumatic › acute or subacute (chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
- Endocarditis › tricuspid › nonrheumatic › acute or subacute (chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
Inclusion terms
Alternative wording in documentation that is classified to I33.9.
- Acute endocarditis NOS
- Acute myoendocarditis NOS
- Acute periendocarditis NOS
- Subacute endocarditis NOS
- Subacute myoendocarditis NOS
- Subacute periendocarditis NOS
Excludes1 — never code together — inherited from I33
The conditions below can never be reported together with I33.9 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
Excludes2 — not included here — inherited from Chapter 9
The conditions below are not part of I33.9, but a patient may have both at the same time. When documentation supports it, I33.9 and the excluded code may both be reported.
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
- systemic connective tissue disorders (M30-M36)
- transient cerebral ischemic attacks and related syndromes (G45.-)
How long has I33.9 existed?
I33.9 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.