2027 ICD-10-CM Diagnosis Code G31.83Neurocognitive disorder with Lewy bodies

ICD-10-CM Codes›G00–G99›G30-G32›G31

ICD-10-CM G31.83
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G31.83 is a billable ICD-10-CM diagnosis code for neurocognitive disorder with Lewy bodies. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 56 through 57. Coders also document this condition as dementia due to Lewy body disease. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Neurocognitive disorders.

For Medicare Advantage risk adjustment, G31.83 maps to CMS-HCC Category 127 (Dementia, Mild or Unspecified) under the V28 model, adding a risk factor of about 0.341 for a community, non-dual, aged beneficiary in payment year 2027.

Code Identity

ICD-10-CM Code
G31.83
Billable Status
Yes — Valid for Submission
Code Describes
Neurocognitive disorder with Lewy bodies
Short Description
Neurocognitive disorder with Lewy bodies
Same as the full description in the CMS dataset.
Parent Code
G31.8
Other specified degenerative diseases of nervous system

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG30-G32Other degenerative diseases of the nervous system
CategoryG31Other degenerative diseases of nervous system, not elsewhere classified
This CodeG31.83Neurocognitive disorder with Lewy bodies

Medicare Risk Adjustment (HCC)Billing

G31.83 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 127— Dementia, Mild or Unspecified
Payment HCC · PY 2027 one of 65 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.341
community, non-dual, aged · ranges 0.000–0.438 across segments
Hierarchy
Superseded by HCC 125 and HCC 126
a more severe related category takes the payment when both are reported
Prior Model (CMS-HCC V24)
HCC 52
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
ESRD (V21): HCC 52 · ESRD (V24): HCC 52
ESRD V21 weights: 0.045 dialysis, 0.000–0.328 functioning graft · ESRD V24 weights: 0.042 dialysis, 0.000–0.399 functioning graft
Part D (RxHCC)
RxHCC 112 — Dementia, Except Alzheimer's 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.

  • Dementia due to Lewy body disease
  • Dementia with behavioral disturbance
  • Diffuse Lewy body disease with spongiform cortical change
  • Disorder of autonomic nervous system due to senile dementia of Lewy body type
  • Early onset dementia due to Lewy body disease
  • Late onset dementia due to Lewy body disease
  • Lewy body dementia with behavioral disturbance
  • Lewy body disease
  • Parkinsonism with dementia of Guadeloupe

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G31.83: its own notes plus those printed at G31 and Chapter 6. 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.

  • Lewy body dementia
  • Lewy body disease

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 G31 Other degenerative diseases of nervous system, not elsewhere classified applies to 14 codes
From Chapter 6 (G00-G99) Diseases of the nervous system applies to 700 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)

Use Additional Code

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

On G31.83 itself
  • code, if applicable, to identify mild neurocognitive disorders due to known physiological condition (F06.7-)
From G31 Other degenerative diseases of nervous system, not elsewhere classified applies to 14 codes

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

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name G31.83, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming G31.83: they are not reported together with it, unless the two conditions are unrelated.

  • G21 Secondary parkinsonism
    neurocognitive disorder with Lewy bodies (G31.83)

Code First 2

These codes say to code first a condition named in the note, and G31.83 is one of the conditions named.

  • F02 Dementia in other diseases classified elsewhere
    neurocognitive disorder with Lewy bodies (G31.83)
  • F06.7 Mild neurocognitive disorder due to known physiological condition
    Neurocognitive disorder with Lewy bodies (G31.83)

Use Additional Code 1

These codes say to use an additional code from the note, and G31.83 is one of the codes named.

  • G31 Other degenerative diseases of nervous system, not elsewhere classified
    code, if applicable, for codes G31.0-G31.83, G31.85-G31.9, to identify: names G31.0-G31.83, 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 NVS011
Neurocognitive disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Lewy Body Dementia

Lewy body dementia (LBD) is one of the most common types of dementia in older adults. Dementia is a loss of mental functions that is severe enough to affect your daily life and activities. These functions include:

The full article covers:

  • What is Lewy body dementia (LBD)?
  • What are the types of Lewy body dementia (LBD)?
  • What causes Lewy body dementia (LBD)?
  • Who is at risk for Lewy body dementia (LBD)?
  • What are the symptoms of Lewy body dementia (LBD)?
  • How is Lewy body dementia (LBD) diagnosed?
  • What are the treatments for Lewy body dementia (LBD)?

Read the full article at MedlinePlus

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

Convert G31.83 to ICD-9-CMHistory

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

ICD-9-CM
331.82 Dementia w Lewy bodies
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2022No changes
FY 2023RevisedCode revised
FY 2024–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About G31.83Overview

What is the ICD-10 code for neurocognitive disorder with Lewy bodies?

The ICD-10-CM code for neurocognitive disorder with Lewy bodies is G31.83 (sometimes written as G3183). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is G31.83 (Other specified degenerative diseases of nervous system) a billable code?

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

What MS-DRG does G31.83 group to?

When neurocognitive disorder with Lewy bodies is the principal diagnosis on an inpatient stay, it groups to MS-DRG 57, 56, with relative weights from 1.2835 to 2.2649 depending on complications. Higher weights mean higher Medicare reimbursement.

Does G31.83 need an additional code?

When the condition applies, yes. The Use Additional Code note reads: code, if applicable, to identify mild neurocognitive disorders due to known physiological condition (F06.7-). The additional code is reported after G31.83.

What is the ICD-9 equivalent of G31.83?

Under the General Equivalence Mappings, neurocognitive disorder with Lewy bodies converts to ICD-9-CM 331.82 (dementia w Lewy bodies). The mapping is a direct match.

What HCC is G31.83?

G31.83 (neurocognitive disorder with Lewy bodies) maps to CMS-HCC Category 127 (Dementia, Mild or Unspecified), commonly written as HCC 127, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 52 under the retired V24 model. It also maps in the ESRD (V21) and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 112.

Does G31.83 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, G31.83 adds a risk adjustment factor of about 0.341 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.000 to 0.438 depending on the payment segment). A more severe related category (HCC 125 and HCC 126) supersedes it when both are reported. See the full factor table on the HCC 127 category page.