2027 ICD-10-CM Diagnosis Code I33Acute and subacute endocarditis

ICD-10-CM Codes›I00–I99›I30-I5A›I33

ICD-10-CM I33
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

I33 is a non-billable ICD-10-CM category code for acute and subacute endocarditis, so it cannot be submitted on claims. Use a more specific code from this category instead, such as I33.0 and I33.9.

Code Identity

ICD-10-CM Code
I33
Billable Status
No — Non-Billable Category
Code Describes
Acute and subacute endocarditis
Short Description
Acute and subacute endocarditis
Same as the full description in the CMS dataset.
Chapter
I30-I5A
Other forms of heart disease

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI30-I5AOther forms of heart disease
CategoryI33Acute and subacute endocarditis
This CodeI33Acute and subacute endocarditis

Specific Coding for Acute and subacute endocarditisOverview

Non-specific codes like I33 require more characters. Use one of these billable codes instead:

  • Use I33.0 for Acute and subacute infective endocarditis

  • Use I33.9 for Acute and subacute endocarditis, unspecified

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to I33: its own notes plus those printed at Chapter 9. A note printed at a category, block or chapter applies to every code under it.

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

  • acute rheumatic endocarditis (I01.1)
  • endocarditis NOS (I38)

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 9 (I00-I99) Diseases of the circulatory system applies to 1,433 codes
  • 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.-)

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

Patient EducationClinical

Endocarditis

Endocarditis is sometimes called infective endocarditis. It's a rare but life-threatening inflammation of the lining inside your heart's chambers and valves (the endocardium).

The full article covers:

  • What is endocarditis?
  • What causes endocarditis?
  • Who is more likely to develop endocarditis?
  • What are the symptoms of endocarditis?
  • What other problems can endocarditis cause?
  • How is endocarditis diagnosed?
  • What are the treatments for endocarditis?
  • Can endocarditis 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 I33Overview

What is the ICD-10 code for acute and subacute endocarditis?

I33 is the ICD-10-CM category for acute and subacute endocarditis, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is I33 (Acute and subacute endocarditis) a billable code?

No. This is a category header that groups the codes for acute and subacute endocarditis, and headers cannot be submitted on claims. Claims for acute and subacute endocarditis need a more specific code from this category, such as I33.0 and I33.9.

Can I33 be reported with I01.1?

Not as a rule. The Excludes1 note on I33 lists "acute rheumatic endocarditis (I01.1)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).