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I20.0 ICD-10-CM Code: Unstable angina

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
6 inclusion terms · 3 Excludes1 · 6 use-additional codes · 1 code-also instruction
Risk adjustment
CMS-HCC V28: 1 category · CMS-HCC V22 category 87 · RxHCC V08 category 188

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v44, Appendix B.

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 229 — Unstable Angina and Other Acute Ischemic Heart Disease

Other models: CMS-HCC V22 HCC 87 · RxHCC V08 HCC 188

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for I20.0 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2027Effective: October 1, 2026

Trace:FY2027 changesChange historyRelease, file and checksum

Notes without a marker are published on I20.0 itself; “inherited from” names the category or block whose note applies here.

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Accelerated angina
  • Crescendo angina
  • De novo effort angina
  • Intermediate coronary syndrome
  • Preinfarction syndrome
  • Worsening effort angina

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Source: inherited from I20

Code Also

Additional codes that may be required to fully describe the encounter.

  • the presence of hypertension (I10-I1A)

Source: inherited from I20-I25

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional code to identify:
  • exposure to environmental tobacco smoke (Z77.22)
  • history of tobacco dependence (Z87.891)
  • occupational exposure to environmental tobacco smoke (Z57.31)
  • tobacco dependence (F17.-)
  • tobacco use (Z72.0)

Source: inherited from I20

Coder workflow for I20.0

MedCoder structured workflow — derived from this code’s own official record

Before you code I20.0

  1. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with I20.0. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the documentation support a condition named in I20.0’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewI25.1, I25.7, I23.7

Consider I20.0. Then work the Use Additional Code note and review the Code Also note, and confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
The conditions the Use Additional Code note names
Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.

Official instructions as workflow

  • Excludes1 — check before selecting I20.0(3 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with I20.0: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareI25.1, I25.7, I23.7

    See the official tabular notes · Guidelines I.A.12.a

  • Use Additional Code — after identifying I20.0(6 notes)

    Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with I20.0 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

    ReviewZ77.22, Z87.891, Z57.31, F17, Z72.0

    See the official tabular notes · Guidelines I.A.13

  • Code Also — related condition(1 note)

    Coding workflow: Review the related condition when both are documented and the instruction applies. A Code Also note does not fix sequencing; the order follows the circumstances of the encounter.

    See the official tabular notes · Guidelines I.A.17

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: Both the condition I20.0 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewI25.1, I25.7, I23.7

Documentation: A condition the Use Additional Code note names is documented.

Coding question: Is a second code reported with I20.0?

Path: Review the Use Additional Code note and the code it names.

Reason: The additional code is reported when the record documents the condition; a conditional instruction applies only when its condition is met (Guidelines I.A.13).

ReviewZ77.22, Z87.891, Z57.31, F17, Z72.0

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Don’t confuse I20.0 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of I20.0 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

  • I25.1— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of angina pectoris with atherosclerotic heart disease of native coronary arteries moves the case to I25.1; the two are not reported together unless documented as unrelated.

    Full comparison: I20.0 vs I25.1 →

  • I25.7— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of atherosclerosis of coronary artery bypass graft(s) and coronary artery of transplanted heart with angina pectoris moves the case to I25.7; the two are not reported together unless documented as unrelated.

    Full comparison: I20.0 vs I25.7 →

  • I23.7— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of postinfarction angina moves the case to I23.7; the two are not reported together unless documented as unrelated.

    Full comparison: I20.0 vs I23.7 →

  • I20.9— Specificity relationship (Review)

    Overlapping diagnoses in the same category.

    Overlapping codes in the same category — the documentation decides which is the more specific fit.

    What moves you there: A record that documents no more than “Angina pectoris, unspecified” takes I20.9; specificity in the record moves it back here.

    Full comparison: I20.0 vs I20.9 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Code Overview

Unstable angina is a billable ICD-10-CM diagnosis code (I20.0).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Indexed Clinical Terms (8)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Decision Points

The directives on this code's own record, as a pre-claim checklist.

  1. 6 Use Additional Code instructions — report the named additional code(s) when the documentation supports them. See the Use Additional Code notes
  2. 1 Code Also note — a second code may apply; the guidelines leave its sequencing to the circumstances of the encounter. See the Code Also notes
  3. 3 Excludes1 entries — codes named there are generally not reported together with this code (Guidelines I.A.12.a). See the Excludes1 notes

Checklist rows are derived from this code's own official directives; the wording of each check is MedCoder editorial. The official notes themselves are in the sections each row links to.

Verify Before Coding

  • CC as a secondary diagnosis (FY2027). Can raise the stay's MS-DRG severity tier.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name I20.0 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 7 Excludes1 notes: I24 — Other acute ischemic heart diseases (via I20.-), I25.110 — Atherosclerotic heart disease of native coronary artery with unstable angina pectoris, I25.700 — Atherosclerosis of coronary artery bypass graft(s), unspecified, with unstable angina pectoris, I25.710 — Atherosclerosis of autologous vein coronary artery bypass graft(s) with unstable angina pectoris, I25.720 — Atherosclerosis of autologous artery coronary artery bypass graft(s) with unstable angina pectoris, I25.730 — Atherosclerosis of nonautologous biological coronary artery bypass graft(s) with unstable angina pectoris, I25.790 — Atherosclerosis of other coronary artery bypass graft(s) with unstable angina pectoris.

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

MS-DRG Grouper Relationships (FY2027)

Potential MS-DRG participation — not a DRG assignment.

FY2027 MS-DRG: CC — Complication or Comorbidity. Reported as a secondary diagnosis, this code raises the stay's MS-DRG severity tier — except when the principal diagnosis is one of 64 clinically related codes on its CMS exclusion list.

Named in the grouper logic of 1 MS-DRG: DRG 311 (MDC 05).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):CIR011 — Coronary atherosclerosis and other heart disease (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical process (MS-DRG)

Acts as CC — raises the severity of other admissions. CMS groups these diagnoses into one MS-DRG principal-diagnosis exclusion process — a CC/MCC on this list never raises severity when the principal diagnosis is also on it.

I09.81 — Rheumatic heart failure, I11.0 — Hypertensive heart disease with heart failure, I13.0 — Hypertensive heart and chronic kidney disease with heart failure and stage 1 through stage 4 chronic kidney disease, or unspecified chronic kidney disease, I13.2 — Hypertensive heart and chronic kidney disease with heart failure and with stage 5 chronic kidney disease, or end stage renal disease, I20.1 — Angina pectoris with documented spasm, I20.2 — Refractory angina pectoris, I20.81 — Angina pectoris with coronary microvascular dysfunction, I20.89 — Other forms of angina pectoris, I20.9 — Angina pectoris, unspecified, I21.01 — ST elevation (STEMI) myocardial infarction involving left main coronary artery, I21.02 — ST elevation (STEMI) myocardial infarction involving left anterior descending coronary artery, I21.09 — ST elevation (STEMI) myocardial infarction involving other coronary artery of anterior wall, I21.11 — ST elevation (STEMI) myocardial infarction involving right coronary artery, I21.19 — ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall, I21.21 — ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery, I21.29 — ST elevation (STEMI) myocardial infarction involving other sites, I21.3 — ST elevation (STEMI) myocardial infarction of unspecified site, I21.4 — Non-ST elevation (NSTEMI) myocardial infarction, I21.9 — Acute myocardial infarction, unspecified, I21.A1 — Myocardial infarction type 2, +43 more

Same CMS-HCC risk category (V28)

CMS maps these diagnoses to the same Hierarchical Condition Category (Unstable Angina and Other Acute Ischemic Heart Disease) for risk-adjusted payment.

I23.0 — Hemopericardium as current complication following acute myocardial infarction, I23.1 — Atrial septal defect as current complication following acute myocardial infarction, I23.2 — Ventricular septal defect as current complication following acute myocardial infarction, I23.3 — Rupture of cardiac wall without hemopericardium as current complication following acute myocardial infarction, I23.4 — Rupture of chordae tendineae as current complication following acute myocardial infarction, I23.5 — Rupture of papillary muscle as current complication following acute myocardial infarction, I23.6 — Thrombosis of atrium, auricular appendage, and ventricle as current complications following acute myocardial infarction, I23.7 — Postinfarction angina, I23.8 — Other current complications following acute myocardial infarction, I24.0 — Acute coronary thrombosis not resulting in myocardial infarction, I24.1 — Dressler's syndrome, I24.81 — Acute coronary microvascular dysfunction, I24.89 — Other forms of acute ischemic heart disease, I24.9 — Acute ischemic heart disease, unspecified, I25.110 — Atherosclerotic heart disease of native coronary artery with unstable angina pectoris, I25.700 — Atherosclerosis of coronary artery bypass graft(s), unspecified, with unstable angina pectoris, I25.710 — Atherosclerosis of autologous vein coronary artery bypass graft(s) with unstable angina pectoris, I25.720 — Atherosclerosis of autologous artery coronary artery bypass graft(s) with unstable angina pectoris, I25.730 — Atherosclerosis of nonautologous biological coronary artery bypass graft(s) with unstable angina pectoris, I25.750 — Atherosclerosis of native coronary artery of transplanted heart with unstable angina, +4 more

Related risk categories

These categories interact through CMS's HCC hierarchy — one can suppress the other's risk-adjustment weight when both are present on a claim.

Acute Myocardial Infarction

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Coronary atherosclerosis and other heart disease).

I20.1 — Angina pectoris with documented spasm, I20.2 — Refractory angina pectoris, I20.8 — Other forms of angina pectoris, I20.81 — Angina pectoris with coronary microvascular dysfunction, I20.89 — Other forms of angina pectoris, I20.9 — Angina pectoris, unspecified, I24.0 — Acute coronary thrombosis not resulting in myocardial infarction, I24.8 — Other forms of acute ischemic heart disease, I24.81 — Acute coronary microvascular dysfunction, I24.89 — Other forms of acute ischemic heart disease, I24.9 — Acute ischemic heart disease, unspecified, I25.10 — Atherosclerotic heart disease of native coronary artery without angina pectoris, I25.110 — Atherosclerotic heart disease of native coronary artery with unstable angina pectoris, I25.111 — Atherosclerotic heart disease of native coronary artery with angina pectoris with documented spasm, I25.112 — Atherosclerotic heart disease of native coronary artery with refractory angina pectoris, I25.118 — Atherosclerotic heart disease of native coronary artery with other forms of angina pectoris, I25.119 — Atherosclerotic heart disease of native coronary artery with unspecified angina pectoris, I25.2 — Old myocardial infarction, I25.5 — Ischemic cardiomyopathy, I25.6 — Silent myocardial ischemia, +47 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Infarct, infarction”, “Angina”, “Impending”; these codes share that main term but sit in a different category of the Tabular List.

A52.06 — Other syphilitic heart involvement (myocardium, myocardial, syphilitic), A69.1 — Other Vincent's infections (Vincent's), B08.5 — Enteroviral vesicular pharyngitis (aphthous), D73.5 — Infarction of spleen (spleen), E07.89 — Other specified disorders of thyroid (thyroid), E21.4 — Other specified disorders of parathyroid gland (parathyroid gland), E23.6 — Other disorders of pituitary gland (pituitary), E27.49 — Other adrenocortical insufficiency (adrenal), F10.239 — Alcohol dependence with withdrawal, unspecified (delirium tremens), G95.11 — Acute infarction of spinal cord (embolic) (nonembolic) (spinal), I21.01 — ST elevation (STEMI) myocardial infarction involving left main coronary artery (myocardium, myocardial, ST elevation, involving, left main coronary artery), I21.02 — ST elevation (STEMI) myocardial infarction involving left anterior descending coronary artery (myocardium, myocardial, ST elevation, involving, diagonal coronary artery), I21.09 — ST elevation (STEMI) myocardial infarction involving other coronary artery of anterior wall (myocardium, myocardial, ST elevation, anterior), I21.11 — ST elevation (STEMI) myocardial infarction involving right coronary artery (myocardium, myocardial, transmural, inferoposterior), I21.19 — ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall (myocardium, myocardial, transmural, inferior NEC), I21.21 — ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery (myocardium, myocardial, ST elevation, involving, left circumflex coronary artery), I21.29 — ST elevation (STEMI) myocardial infarction involving other sites (myocardium, myocardial, ST elevation, septal), I21.3 — ST elevation (STEMI) myocardial infarction of unspecified site (myocardium, myocardial, Q wave), I21.4 — Non-ST elevation (NSTEMI) myocardial infarction (nontransmural), I21.9 — Acute myocardial infarction, unspecified (myocardium, myocardial), +67 more

Lab tests where this diagnosis supports Medicare coverage (NCD)

Medicare's National Coverage Determination (NCD) program lists this diagnosis as medical justification for these lab tests.

Lipid Panel, Prothrombin Time Test and INR (PT/INR)

Contextual Map

Every relationship of I20.0 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run I20.0 with these 7 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Clinical classification (CCSR)

Risk adjustment (CMS-HCC)

  • HCC 229 — Unstable Angina and Other Acute Ischemic Heart Disease [CMS-HCC]— CMS-HCC V28 · 2026

MS-DRG Grouper

  • CC — Complication or Comorbidity [MS-DRG severity]: “As a secondary diagnosis this code can raise the stay's MS-DRG severity tier (CC).”— CMS MS-DRG Definitions Manual (Appendix C) · FY2027
  • DRG 311 — ANGINA PECTORIS[MS-DRG]: “ANGINA PECTORIS (MDC 05)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2027

MDC crossing

  • MDC 05 — Diseases and Disorders of the Circulatory System[MDC crossing]: “Diseases and Disorders of the Circulatory System — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 15,708 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2027

Index entries

  • Angina (attack) (cardiac) (chest) (heart) (pectoris) (syndrome) (vasomotor), unstable[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Impending, coronary syndrome[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Impending, myocardial infarction[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Infarct, infarction, impending (myocardium)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Syndrome, coronary, insufficiency or intermediate[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Syndrome, impending coronary[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Syndrome, intermediate coronary (artery)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Syndrome, preinfarction[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v44 Release, file and checksum · Publisher’s page
Risk adjustment Official source data
2026 Mid-Year Final ICD-10 Mappings + Model Software (cms.gov/files/zip/2026-midyear-final-icd-10-mappings.zip, 2026-midyear-final-model-software.zip) — CMS-HCC V28, PY2026 mid-year final release Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "I20.0 — Unstable angina." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/i20.0-unstable-angina

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Unstable angina

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027, and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to I20.0 in its code family, with their registry titles.

View all codes in the I20 family