What is ICD-10 code I77.6?

I77.6 is the ICD-10-CM diagnosis code for Arteritis, unspecified. Inflammation of an artery when the specific type or location is not specified or documented. It belongs to the ICD-10-CM chapter for diseases of the circulatory system (i00-i99). I77.6 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. I77.6 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. I77.6 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. I77.6 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for I77.6?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. I77.6 was a payment HCC under V24 (Vascular Disease) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting I77.6?

Use this code only when the type of arteritis cannot be determined or is not specified Consider if more specific arteritis codes apply (e.g., temporal arteritis, Takayasu arteritis) Because I77.6 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

2026 ICD-10-CM I77.6: Arteritis, unspecified

ICD-10-CM Code View

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Code lookupI77.6Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the circulatory system (I00-I99) / Diseases of arteries, arterioles and capillaries (I70-I79)

I77.6

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Arteritis, unspecified

Inflammation of an artery when the specific type or location is not specified or documented.

Buddy Insight

Arteritis, unspecified, represents inflammation of arterial walls that can lead to stenosis, occlusion, or aneurysm formation.

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Mapped

HCC 108

Vascular Disease

RAF 0.288

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

Mapped

HCC 108

Vascular Disease

RAF 0.073

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

I77Other disorders of arteries and arterioles

I77.6Arteritis, unspecified

Inclusion Terms

Official

Aortitis NOS
Endarteritis NOS

Excludes 2

Official

collagen (vascular) diseases (M30-M36)
hypersensitivity angiitis (M31.0)
pulmonary artery (I28.-)

Related Child Codes

Official

I77.0Arteriovenous fistula, acquired

I77.1Stricture of artery

I77.2Rupture of artery

I77.3Arterial fibromuscular dysplasia

I77.4Celiac artery compression syndrome

Includes

Official

ICD-10-CM does not list Includes notes for I77.6 in this effective period.

Excludes 1

Official

arteritis or endarteritis:
aortic arch (M31.4)
cerebral NEC (I67.7)
coronary (I25.89)
deformans (I70.-)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for I77.6 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for I77.6 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for I77.6 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Clinical documentation of arterial inflammation with supporting evidence

Diagnostic workup results including inflammatory markers (erythrocyte sedimentation rate, C-reactive protein)

Specification of affected arteries when known

Exclusion of more specific arteritis diagnoses (giant cell, Takayasu, antineutrophilic cytoplasmic antibody-associated)

MEAT Support

HCC Buddy guidance

Clinical documentation of arterial inflammation with supporting evidence

Diagnostic workup results including inflammatory markers (erythrocyte sedimentation rate, C-reactive protein)

Specification of affected arteries when known

Exclusion of more specific arteritis diagnoses (giant cell, Takayasu, antineutrophilic cytoplasmic antibody-associated)

Audit Caution

HCC Buddy guidance

Using this unspecified code when a more specific arteritis diagnosis is documented in the record

Failing to query the provider for the type of arteritis to enable more specific coding

Confusing arteritis with atherosclerosis — arteritis is inflammatory while atherosclerosis is degenerative

Not distinguishing from vasculitis codes that may be more appropriate for small vessel involvement

Common Mistakes

HCC Buddy guidance

M31.6 — Other giant cell arteritis: use when temporal or cranial arteritis is documented

M31.4 — Aortic arch syndrome (Takayasu): use for Takayasu arteritis specifically

I77.82 — Antineutrophilic cytoplasmic antibody vasculitis: use when antineutrophilic cytoplasmic antibody-associated vasculitis is documented

I77.5 — Necrosis of artery: use when there is tissue death of the arterial wall

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 I77.6 an HCC code?

Yes. I77.6 maps to Vascular Disease under the V24 model but is not retained in V28.

Code: I77.6
Description: Arteritis, unspecified
HCC (V28): No CMS-HCC V28 mapping
RAF: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

V24HCC 108, Vascular Disease

0.288

ESRDHCC 108, Vascular Disease

0.073

Each model's RAF is its CMS base weight for that model's standard population, so 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 segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work I77.6 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for I77.6

For I77.6 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

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

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed I77.6 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

I77.6 is the ICD-10-CM diagnosis code for arteritis, unspecified. Inflammation of an artery when the specific type or location is not specified or documented. I77.6 sits in the ICD-10-CM chapter for diseases of the circulatory system (i00-i99), within the section covering diseases of arteries, arterioles and capillaries (i70-i79).

Under the older CMS-HCC V24 model, I77.6 maps to Vascular Disease (HCC 108) with a community, non-dual, aged base RAF weight of 0.288. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Use this code only when the type of arteritis cannot be determined or is not specified. Because I77.6 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. 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, RAF weights, and MEAT documentation criteria for I77.6 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use this code only when the type of arteritis cannot be determined or is not specified
•Consider if more specific arteritis codes apply (e.g., temporal arteritis, Takayasu arteritis)

Clinical Significance

Arteritis, unspecified, represents inflammation of arterial walls that can lead to stenosis, occlusion, or aneurysm formation. While this is an unspecified code, it still captures significant vascular disease that increases patient complexity and resource needs. Providers should be queried for more specific diagnoses such as giant cell arteritis or Takayasu arteritis when possible.

Documentation Requirements

✓Clinical documentation of arterial inflammation with supporting evidence
✓Diagnostic workup results including inflammatory markers (erythrocyte sedimentation rate, C-reactive protein)
✓Specification of affected arteries when known
✓Exclusion of more specific arteritis diagnoses (giant cell, Takayasu, antineutrophilic cytoplasmic antibody-associated)
✓Current treatment plan and monitoring schedule

Excludes 1, Do NOT code together

arteritis or endarteritis:
aortic arch (M31.4)
cerebral NEC (I67.7)
coronary (I25.89)
deformans (I70.-)
giant cell (M31.5, M31.6)
obliterans (I70.-)
senile (I70.-)

Commonly Confused Codes

•M31.6: Other giant cell arteritis: use when temporal or cranial arteritis is documented
•M31.4: Aortic arch syndrome (Takayasu): use for Takayasu arteritis specifically
•I77.82: Antineutrophilic cytoplasmic antibody vasculitis: use when antineutrophilic cytoplasmic antibody-associated vasculitis is documented
•I77.5: Necrosis of artery: use when there is tissue death of the arterial wall