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E66.813 ICD-10-CM Code: Obesity, class 3

E66.813 maps to CMS-HCC V28 48. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software

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HCC Buddy Code Card

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Code lookupE66.813

FY 2026 Apr update / Endocrine, nutritional and metabolic diseases (E00-E89) / Overweight, obesity and other hyperalimentation (E65-E68)

E66.813

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

Obesity, class 3

Class 3 obesity, the most severe level of obesity typically defined as BMI 40 or higher.

Buddy the Bee presenting code insight

Buddy Insight

Obesity class 3 represents the most severe classification of obesity based on body mass index of 40 or higher.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 48

Coefficient HCC 48: 0.186 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

N/A

—

Not mapped

ESRD/PACE

HCC 22

Code-level coefficient reference

RXHCC

N/A

—

Not mapped

Code Book Path

Official
E66.8Other obesityE66.81Obesity classE66.813Obesity, class 3

Inclusion Terms

Official

No inclusion terms are included in this display for E66.813. Check the code and parent instructions in the Code Book.

Excludes 2

Official
  • adiposogenital dystrophy (E23.6)Inherited from E66
  • lipomatosis dolorosa [Dercum] (E88.2)Inherited from E66
  • lipomatosis NOS (E88.2)Inherited from E66
  • Prader-Willi syndrome (Q87.11)Inherited from E66

Related Codes

Official
E66.811Obesity, class 1E66.812Obesity, class 2

Includes

Official

No Includes notes are included in this display for E66.813. Check the code and parent instructions in the Code Book.

Excludes 1

Official
  • transitory endocrine and metabolic disorders specific to newborn (P70-P74)Inherited from E00-E89

Code First

Official
  • obesity complicating pregnancy, childbirth and the puerperium, if applicable (O99.21-)Inherited from E66

Use Additional

Official
  • code to identify body mass index (BMI), if known, for adults (Z68.1-Z68.45) or pediatrics (Z68.5-)Inherited from E66

Code Also

Official

No Code Also instructions are included in this display for E66.813. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Documentation must include a specific body mass index of 40 or higher with a Z68.4x code assigned additionally.
The provider should document the diagnosis of class 3 or severe obesity explicitly.
Associated comorbidities, current weight management strategies, and any referrals for bariatric evaluation should be documented.
The clinical impact of obesity on the patient's overall health status should be noted.

MEAT Support

HCC Buddy guidance
Documentation must include a specific body mass index of 40 or higher with a Z68.4x code assigned additionally.
The provider should document the diagnosis of class 3 or severe obesity explicitly.
Associated comorbidities, current weight management strategies, and any referrals for bariatric evaluation should be documented.
The clinical impact of obesity on the patient's overall health status should be noted.

Audit Caution

HCC Buddy guidance
Do not assign both E66.01 and E66.813 simultaneously, as they represent overlapping concepts of severe obesity.
Choose one based on provider documentation preferences.
Always add the corresponding Z68.4x body mass index code.
Do not assign class 3 obesity without a documented body mass index of 40 or above.

Common Mistakes

HCC Buddy guidance
E66.01 (Morbid obesity due to excess calories) is an overlapping code that should not be assigned simultaneously.
E66.2 (Morbid obesity with alveolar hypoventilation) includes the respiratory component.
E66.811 (Obesity, class 1) and E66.812 (Obesity, class 2) represent lower body mass index ranges.
E66.09 (Other obesity due to excess calories) is for non-morbid obesity.

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 E66.813 an HCC code?

Yes. E66.813 (Obesity, class 3) maps to HCC 48, Morbid Obesity under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.186. 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: E66.813 is billable and maps to V28 HCC 48, Morbid Obesity. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
E66.813
Description
Obesity, class 3
HCC (V28)
HCC 48 — Morbid Obesity
RAF reference coefficient
0.186
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 48, Morbid Obesity
0.186
ESRDHCC 22, Morbid Obesity
Not separately weighted

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 E66.813 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for E66.813

For E66.813, 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

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What This Code Means

E66.813 is the ICD-10-CM diagnosis code for obesity, class 3. Class 3 obesity, the most severe level of obesity typically defined as BMI 40 or higher. E66.813 sits in the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89), within the section covering overweight, obesity and other hyperalimentation (e65-e68).

Under the CMS-HCC V28 risk adjustment model, E66.813 maps to Morbid Obesity (HCC 48) with a source-labeled community, non-dual, aged reference coefficient of 0.186. No V24 mapping is shown for E66.813; use the applicable model and payment year when reviewing the V28 mapping. 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.

Class 3 obesity may also qualify as morbid obesity; review documentation for E66.01 applicability. For E66.813, 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 E66.813 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Class 3 obesity may also qualify as morbid obesity; review documentation for E66.01 applicability
  • •Document BMI ≥40 to support this classification

Clinical Significance

Obesity class 3 represents the most severe classification of obesity based on body mass index of 40 or higher. This classification system aligns with World Health Organization standards and carries the same clinical implications as morbid obesity, including dramatically elevated risks of cardiovascular disease, diabetes mellitus, musculoskeletal disorders, and premature mortality. This code provides an alternative to E66.01 for classifying severe obesity.

Documentation Requirements

  • ✓Documentation must include a specific body mass index of 40 or higher with a Z68.4x code assigned additionally.
  • ✓The provider should document the diagnosis of class 3 or severe obesity explicitly.
  • ✓Associated comorbidities, current weight management strategies, and any referrals for bariatric evaluation should be documented.
  • ✓The clinical impact of obesity on the patient's overall health status should be noted.

Commonly Confused Codes

  • •E66.01 (Morbid obesity due to excess calories) is an overlapping code that should not be assigned simultaneously.
  • •E66.2 (Morbid obesity with alveolar hypoventilation) includes the respiratory component.
  • •E66.811 (Obesity, class 1) and E66.812 (Obesity, class 2) represent lower body mass index ranges.
  • •E66.09 (Other obesity due to excess calories) is for non-morbid obesity.
  • •Z68.4x codes are supplementary body mass index codes, not standalone diagnoses.

Child Codes

E66.811Obesity, class 1
E66.812Obesity, class 2
E66.813Obesity, class 3
HCC 48

Code Hierarchy

└E66Overweight and obesity└E66.8Other obesity└E66.81Obesity class└E66.813Obesity, class 3
└E66.813Obesity, class 3

E66.813 code history

Code setChange
FY2025 (effective Oct 1, 2024)Added to the code set

Source: official CMS ICD-10-CM order and addenda files, FY2016 through FY2027.

Also searched as

  • E66 813
  • E66813

For E66.813, 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.

E66.813 maps to CMS-HCC V28 category 48, Morbid Obesity. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for E66.813. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

More on E66.813

Code family

Every E66 code with its CMS-HCC V28 statusOverweight and obesity, 10 billable codes

Related condition guides

Referenced in blog posts

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