ICD10BillableValid for clinical use

ICD-10 Code I33.9: Acute and subacute endocarditis, unspecified

I33.9 is a billable ICD-10 diagnosis code used to classify Acute and subacute endocarditis, unspecified in medical records and claims. You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records. ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Diseases of the circulatory system (I00-I99).

Reviewed by HealthAssure Clinical TeamUpdated 26 May 2026

What is this code?

ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Diseases of the circulatory system (I00-I99).

When is it used?

  • May be used when a clinician documents acute and subacute endocarditis, unspecified in a patient's medical record.
  • May appear in hospital records, claims, referrals, and clinical documentation.
  • This code can be used as a clinically usable diagnosis entry in standardized coding workflows.

What it does not mean

  • A code alone does not explain severity, treatment plan, or outcome.
  • A medical code should not be treated as a substitute for a doctor's diagnosis or advice.

Code hierarchy

chapter
9Diseases of the circulatory system (I00-I99)
block
I30-I5AOther forms of heart disease
category
I33Acute and subacute endocarditis
currentI33

Official coding notes

Inclusion terms
  • Acute endocarditis NOS
  • Acute myoendocarditis NOS
  • Acute periendocarditis NOS
  • Subacute endocarditis NOS
  • Subacute myoendocarditis NOS
  • Subacute periendocarditis NOS

Where you may see this code

You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records.

Related specialists

CardiologistGeneral Physician

Coverage-related procedures and services

CPT 93325high
DOPPLER ECHOCARDIOGRAPHY COLOR FLOW VELOCITY MAPPING (LIST SEPARATELY IN ADDITION TO CODES FOR ECHOCARDIOGRAPHY)
Source: CMS coverage guidance
CPT 93320high
DOPPLER ECHOCARDIOGRAPHY, PULSED WAVE AND/OR CONTINUOUS WAVE WITH SPECTRAL DISPLAY (LIST SEPARATELY IN ADDITION TO CODES FOR ECHOCARDIOGRAPHIC IMAGING); COMPLETE
Source: CMS coverage guidance
CPT 93321high
DOPPLER ECHOCARDIOGRAPHY, PULSED WAVE AND/OR CONTINUOUS WAVE WITH SPECTRAL DISPLAY (LIST SEPARATELY IN ADDITION TO CODES FOR ECHOCARDIOGRAPHIC IMAGING); FOLLOW-UP OR LIMITED STUDY (LIST SEPARATELY IN ADDITION TO CODES FOR ECHOCARDIOGRAPHIC IMAGING)
Source: CMS coverage guidance
CPT 93306high
ECHOCARDIOGRAPHY, TRANSTHORACIC, REAL-TIME WITH IMAGE DOCUMENTATION (2D), INCLUDES M-MODE RECORDING, WHEN PERFORMED, COMPLETE, WITH SPECTRAL DOPPLER ECHOCARDIOGRAPHY, AND WITH COLOR FLOW DOPPLER ECHOCARDIOGRAPHY
Source: CMS coverage guidance
CPT 93307high
ECHOCARDIOGRAPHY, TRANSTHORACIC, REAL-TIME WITH IMAGE DOCUMENTATION (2D), INCLUDES M-MODE RECORDING, WHEN PERFORMED, COMPLETE, WITHOUT SPECTRAL OR COLOR DOPPLER ECHOCARDIOGRAPHY
Source: CMS coverage guidance
CPT 93308high
ECHOCARDIOGRAPHY, TRANSTHORACIC, REAL-TIME WITH IMAGE DOCUMENTATION (2D), INCLUDES M-MODE RECORDING, WHEN PERFORMED, FOLLOW-UP OR LIMITED STUDY
Source: CMS coverage guidance

Coding guidelines

Compatibility

Legacy and official ICD code match exactly.
Legacy codes
I33.9

Common synonyms

Acute and subacute endocarditis, unspecifiedAcute and subacute endocarditis

Frequently asked questions

Code details

CodeI33.9
SystemICD10
Display nameAcute and subacute endocarditis, unspecified
ChapterDiseases of the circulatory system (I00-I99)
BlockOther forms of heart disease

Flags

BillableYes
Valid clinical useYes

Source

SourceICD-10
Version2026-annual
Releaseannual
Year2026

Index terms

Matched terms
Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.

ICD-10 Code I33.9 for Acute and subacute endocarditis, unspecified | HealthAssure