2027 ICD-10-CM Diagnosis Code I20.0Unstable angina

ICD-10-CM Codes›I00–I99›I20-I25›I20

ICD-10-CM I20.0
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

I20.0 is a billable ICD-10-CM diagnosis code for unstable angina. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 311. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 64 closely related codes. Coders also document this condition as angina control. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Coronary atherosclerosis and other heart disease.

For Medicare Advantage risk adjustment, I20.0 maps to CMS-HCC Category 229 (Unstable Angina and Other Acute Ischemic Heart Disease) under the V28 model, adding a risk factor of about 0.240 for a community, non-dual, aged beneficiary in payment year 2027.

This medical diagnosis code is frequently used in Cardiology medical specialties to designate conditions such chest pain.

Code Identity

ICD-10-CM Code
I20.0
Billable Status
Yes — Valid for Submission
Code Describes
Unstable angina
Short Description
Unstable angina
Same as the full description in the CMS dataset.
Parent Code
I20
Angina pectoris

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI20-I25Ischemic heart diseases
CategoryI20Angina pectoris
This CodeI20.0Unstable angina

Medicare Risk Adjustment (HCC)Billing

I20.0 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.

CMS-HCC V28 Category (Payment Model)
HCC 229— Unstable Angina and Other Acute Ischemic Heart Disease
Payment HCC · PY 2027 one of 25 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.240
community, non-dual, aged · ranges 0.240–0.458 across segments
Hierarchy
Superseded by HCC 228
a more severe related category takes the payment when both are reported
Prior Model (CMS-HCC V24)
HCC 87
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 87 · ESRD (V21): HCC 87 · ESRD (V24): HCC 87
ESRD V21 weights: 0.116 dialysis, 0.258–0.392 functioning graft · ESRD V24 weights: 0.120 dialysis, 0.209–0.463 functioning graft
Part D (RxHCC)
RxHCC 188 — Coronary Artery Disease
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Angina control
  • Angina control - worsening
  • Chronic chest pain
  • Chronic ischemic heart disease
  • Impending infarction
  • Preinfarction syndrome
  • Progressive angina
  • Refractory angina

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to I20.0: its own notes plus those printed at I20, block I20-I25, and Chapter 9. A note printed at a category, block or chapter applies to every code under it.

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

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

Excludes1

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

From I20 Angina pectoris applies to 6 codes
  • angina pectoris with atherosclerotic heart disease of native coronary arteries (I25.1-)
  • atherosclerosis of coronary artery bypass graft(s) and coronary artery of transplanted heart with angina pectoris (I25.7-)
  • postinfarction angina (I23.7)

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.-)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From I20 Angina pectoris applies to 6 codes
  • 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)

Code Also

A second code may be needed to fully describe the condition; the note gives no sequencing direction.

From Block I20-I25 Ischemic heart diseases applies to 94 codes
  • the presence of hypertension (I10-I1A)

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

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name I20.0, its category, or a range that includes it.

Excludes1 7

These codes carry an Excludes1 note naming I20.0: they are not reported together with it, unless the two conditions are unrelated.

  • I25.110 Atherosclerotic heart disease of native coronary artery with unstable angina pectoris
    unstable angina without atherosclerotic heart disease (I20.0)
  • I25.700 Atherosclerosis of coronary artery bypass graft(s), unspecified, with unstable angina pectoris
    unstable angina pectoris without atherosclerosis of coronary artery bypass graft (I20.0)
  • I25.710 Atherosclerosis of autologous vein coronary artery bypass graft(s) with unstable angina pectoris
    unstable angina without atherosclerosis of autologous vein coronary artery bypass graft(s) (I20.0)
  • I25.720 Atherosclerosis of autologous artery coronary artery bypass graft(s) with unstable angina pectoris
    unstable angina without atherosclerosis of autologous artery coronary artery bypass graft(s) (I20.0)
  • I25.730 Atherosclerosis of nonautologous biological coronary artery bypass graft(s) with unstable angina pectoris
    unstable angina without atherosclerosis of nonautologous biological coronary artery bypass graft(s) (I20.0)
  • I25.790 Atherosclerosis of other coronary artery bypass graft(s) with unstable angina pectoris
    unstable angina without atherosclerosis of other coronary artery bypass graft(s) (I20.0)
  • I24 Other acute ischemic heart diseases
    angina pectoris (I20.-) names I20.-, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR CIR011
Coronary atherosclerosis and other heart disease
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Angina, Unstable

    precordial pain at rest, which may precede a myocardial infarction.

Patient EducationClinical

Angina

Angina is chest pain or discomfort you feel when there is not enough blood flow to your heart muscle. Your heart muscle needs the oxygen that the blood carries. Angina may feel like pressure or a squeezing pain in your chest. It may feel like indigestion. You may also feel pain in your shoulders, arms, neck, jaw, or back.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert I20.0 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
411.1 Intermed coronary synd
Approximate The match is approximate rather than exact.

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 I20.0Overview

What is the ICD-10 code for unstable angina?

The ICD-10-CM code for unstable angina is I20.0 (sometimes written as I200). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is I20.0 (Angina pectoris) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unstable angina on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does I20.0 group to?

When unstable angina is the principal diagnosis on an inpatient stay, it groups to MS-DRG 311 (angina Pectoris), which carries a relative weight of 0.6681. Higher weights mean higher Medicare reimbursement.

Is I20.0 a CC or MCC?

CMS lists I20.0 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 64 closely related codes in its exclusion list.

Can I20.0 be reported with a code from I25.1?

Not as a rule. The Excludes1 note at I20, which applies to I20.0, lists "angina pectoris with atherosclerotic heart disease of native coronary arteries (I25.1-)". 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).

What HCC is I20.0?

I20.0 (unstable angina) maps to CMS-HCC Category 229 (Unstable Angina and Other Acute Ischemic Heart Disease), commonly written as HCC 229, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 87 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 188.

Does I20.0 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, I20.0 adds a risk adjustment factor of about 0.240 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.240 to 0.458 depending on the payment segment). A more severe related category (HCC 228) supersedes it when both are reported. See the full factor table on the HCC 229 category page.