I20.0 ICD-10-CM Code: Unstable angina
I20.0 maps to CMS-HCC V28 229. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Diseases of the circulatory system (I00-I99) / Ischemic heart diseases (I20-I25)
I20.0
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceUnstable angina
Chest pain or discomfort caused by reduced blood flow to the heart that occurs unpredictably, including at rest or with minimal exertion.
Buddy Insight
Unstable angina is an acute coronary syndrome characterized by new-onset, accelerating, or rest angina without evidence of myocardial necrosis (negative troponins).
CMS-HCC V28
MappedHCC 229
Coefficient HCC 229: 0.240 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 132
Code-level coefficient reference
ESRD/PACE
MappedHCC 87
Code-level coefficient reference
RXHCC
MappedHCC 188
Code-level coefficient reference
Code Book Path
Inclusion Terms
Official- Accelerated angina
- Crescendo angina
- De novo effort angina
- Intermediate coronary syndrome
- Preinfarction syndrome
- Worsening effort angina
Excludes 2
Official- certain conditions originating in the perinatal period (P04-P96)Inherited from I00-I99
- certain infectious and parasitic diseases (A00-B99)Inherited from I00-I99
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from I00-I99
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from I00-I99
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from I00-I99
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from I00-I99
- neoplasms (C00-D49)Inherited from I00-I99
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from I00-I99
- systemic connective tissue disorders (M30-M36)Inherited from I00-I99
- transient cerebral ischemic attacks and related syndromes (G45.-)Inherited from I00-I99
Related Codes
Includes
OfficialNo Includes notes are included in this display for I20.0. Check the code and parent instructions in the Code Book.
Excludes 1
Official- angina pectoris with atherosclerotic heart disease of native coronary arteries (I25.1-)Inherited from I20
- atherosclerosis of coronary artery bypass graft(s) and coronary artery of transplanted heart with angina pectoris (I25.7-)Inherited from I20
- postinfarction angina (I23.7)Inherited from I20
Code First
OfficialNo Code First sequencing instructions are included in this display for I20.0. Check the code and parent instructions in the Code Book.
Use Additional
Official- code to identify:Inherited from I20
- exposure to environmental tobacco smoke (Z77.22)Inherited from I20
- history of tobacco dependence (Z87.891)Inherited from I20
- occupational exposure to environmental tobacco smoke (Z57.31)Inherited from I20
- tobacco dependence (F17.-)Inherited from I20
- tobacco use (Z72.0)Inherited from I20
Code Also
Official- the presence of hypertension (I10-I1A)Inherited from I20-I25
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is I20.0 an HCC code?
Yes. I20.0 (Unstable angina) maps to HCC 229, Unstable Angina and Other Acute Ischemic Heart Disease under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.240. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: I20.0 is billable and maps to V28 HCC 229, Unstable Angina and Other Acute Ischemic Heart Disease. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- I20.0
- Description
- Unstable angina
- HCC (V28)
- HCC 229 — Unstable Angina and Other Acute Ischemic Heart Disease
- RAF reference coefficient
- 0.240
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work I20.0 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for I20.0
For I20.0, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Coder workflow notes
Get the V28 mapping + MEAT cheat sheet
One printable reference: check representative V28 mappings and the documentation reminders your note needs. Free, no card.
Free PDF. No card. Unsubscribe anytime.
What This Code Means
I20.0 is the ICD-10-CM diagnosis code for unstable angina. Chest pain or discomfort caused by reduced blood flow to the heart that occurs unpredictably, including at rest or with minimal exertion. I20.0 sits in the ICD-10-CM chapter for diseases of the circulatory system (i00-i99), within the section covering ischemic heart diseases (i20-i25).
Under the CMS-HCC V28 risk adjustment model, I20.0 maps to Unstable Angina and Other Acute Ischemic Heart Disease (HCC 229) with a source-labeled community, non-dual, aged reference coefficient of 0.240. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Unstable angina is a form of acute coronary syndrome; ensure appropriate cardiac workup and troponin testing are documented. For I20.0, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for I20.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Unstable angina is a form of acute coronary syndrome; ensure appropriate cardiac workup and troponin testing are documented
- •Do not assign this code if troponin levels are elevated; use acute MI codes instead
Clinical Significance
Unstable angina is an acute coronary syndrome characterized by new-onset, accelerating, or rest angina without evidence of myocardial necrosis (negative troponins). It represents a high-risk condition with imminent threat of myocardial infarction and requires urgent evaluation and intervention. This carries significant risk adjustment weight reflecting the acute cardiac morbidity and resource intensity.
Documentation Requirements
- ✓Provider diagnosis explicitly stating unstable angina
- ✓Clinical presentation: new onset, crescendo, or rest angina
- ✓Negative cardiac biomarkers (troponin) — if positive, this becomes NSTEMI, not unstable angina
- ✓ECG findings documented (may show ST depression, T-wave inversion, or be normal)
- ✓Risk stratification (TIMI score, HEART score) if documented
- ✓Treatment plan including antiplatelet therapy, anticoagulation, and consideration for cardiac catheterization
- ✓Coronary angiography findings if performed
- ✓Documentation distinguishing from stable angina and NSTEMI
Commonly Confused Codes
- •I20.1: Angina pectoris with documented spasm (Prinzmetal/variant angina: different mechanism)
- •I20.81: Angina pectoris with coronary microvascular dysfunction (microvascular, not epicardial)
- •I20.2: Refractory angina pectoris (chronic refractory pain, not acute unstable presentation)
- •I21.x: Acute myocardial infarction (use when biomarkers ARE positive: indicates myocardial necrosis)
- •I25.110-I25.119: Atherosclerotic heart disease with angina (chronic stable angina, not acute unstable)
- •I20.9: Angina pectoris, unspecified (less specific; use I20.0 when unstable is documented)