Obesity HCC Coding: E66.9 Has No V28 HCC

Quick Answer

E66.9 is a billable ICD-10-CM code. Under CMS-HCC V28 for payment year 2026 it has no payment HCC. The mapping status is verified no-HCC-mapping. E66.811 and E66.812 have the same V28 result. That is the same kind of dead map as F32.9 on the depression guide and N18.9 on the CKD guide.

E66.01, E66.2, and E66.813 map to HCC 48. So do Z68.41, Z68.42, Z68.43, Z68.44, Z68.45, and pediatric Z68.56. Z68.30 and Z68.35 are billable and verified no-HCC-mapping. A BMI of 35 does not create HCC 48.

If the note supports morbid obesity or class 3 obesity and the assigned code is E66.9, that is a documentation and query problem, not a missing map. Do not promote E66.9 to E66.01 from a vital-sign BMI alone.

*Release: FY2026 ICD-10-CM period 2, April 1, 2026 through September 30, 2026. CMS-HCC V28, payment year 2026, is at full weight for non-PACE organizations. Community Non-Dual Aged (CNA) coefficients are shown only where the current CMS source files support them. Interaction terms are applied only inside the RAF tool, so this article does not publish a standalone interaction coefficient.*

At a glance

Checked E66 and Z68 codes. FY2026 period 2 identity plus CMS-HCC V28 mapping:

E66, E66.0, E66.8, E66.81, Z68, Z68.2, Z68.3, Z68.4, and Z68.5 exist in the FY2026 order file as non-billable headings. Code to a billable child. MCP receipts return not applicable for those headings rather than treating them as verified no-map leaf codes.

HCC 48 is labeled "Morbid Obesity." That label and the CNA value 0.186 come from the CMS V28 PY2026 relative-factor file. Other enrollment segments use different coefficients in that same file. Do not treat 0.186 as a universal RAF.

The official V28 hierarchy file lists HCC 48 with no secondary HCC. Checked mapped codes in this article share one payment category. They do not stack.

E66.9 is allowed. It is also a dead V28 map.

The V28 payment map follows the ICD-10-CM code, not the word "obesity."

FY2026 Official Guidelines Section I.A.9.b say unspecified codes are for use when the record is insufficient to assign a more specific code. Section I.B.18 adds that unspecified codes should be reported when they most accurately reflect what is known for that encounter, and that it is inappropriate to select a more specific code the record does not support.

That is why E66.9 remains the correct ICD-10-CM answer when the encounter documents obesity and does not support morbid obesity, class 3 obesity, or another specified E66 term. It is still verified no-HCC-mapping under V28. The coding question and the risk-adjustment question are not the same question.

E66.9 includes "Obesity NOS." E66.3 is overweight. E66.09 is other obesity due to excess calories. E66.89 is other obesity not elsewhere classified. Checked receipts for E66.09, E66.1, E66.3, E66.89, and E66.9 all return verified no-HCC-mapping.

Do not recode E66.9 to E66.01 or E66.813 to "pick up" HCC 48. Severity and class have to be in the provider documentation for the encounter you are coding.

Only three checked E66 leaf codes map to HCC 48

Checked E66.01, E66.2, and E66.813 map to HCC 48. The official CNA is 0.186.

E66.01 is morbid (severe) obesity due to excess calories. It has an Excludes1 note for morbid (severe) obesity with alveolar hypoventilation (E66.2). Official Guidelines Section I.A.12.a define Excludes1 as a pure excludes note: "NOT CODED HERE!" The excluded code is not reported at the same time as the code above the note unless the two conditions are unrelated. E66.01 and E66.2 are not a menu.

E66.2 includes "Obesity hypoventilation syndrome (OHS)" and "Pickwickian syndrome." Official Guidelines Section I.A.15 say the word "with" or "in" means "associated with" or "due to" when it appears in a code title, the Alphabetic Index, or a Tabular instructional note. The classification presumes that link unless the documentation clearly states the conditions are unrelated, or another guideline requires an explicit documented linkage. E66.2 uses "with" in the code title.

E66 has a Code first note for obesity complicating pregnancy, childbirth, and the puerperium, if applicable (O99.21-). Official Guidelines Section I.B.7 say that when there is a Code first note and an underlying condition is present, the underlying condition should be sequenced first, if known. This article does not inventory O99.21. Look up the documented obstetric code.

E66 also has a Use additional note: code to identify body mass index (BMI), if known, for adults (Z68.1-Z68.45) or pediatrics (Z68.5-). Official Guidelines Section I.B.7 say a Use additional code note indicates that a secondary code should be added, if known. Do not skip a supported BMI code because you already have an E66 code.

E66.1 is drug-induced obesity. It has a Use additional note to identify the drug (T36-T50 with fifth or sixth character 5) when an adverse-effect code applies. The checked E66.1 receipt is verified no-HCC-mapping. Do not copy an E66.01 HCC onto it.

E88.82 is named in Official Guidelines Section I.C.4.b as obesity due to disruption of the MC4R pathway. It is billable and verified no-HCC-mapping under V28. It is a different category, not a hidden E66 map.

See Excludes1 versus Excludes2.

Class 3 is more specific than morbid obesity

E66.81 is the non-billable heading for obesity class. The billable children are E66.811 (class 1), E66.812 (class 2), and E66.813 (class 3).

Official Guidelines Section I.C.4.b.1 say the obesity class codes in subcategory E66.81 require a fifth character to convey the severity of obesity. The obesity class should be documented in the medical record by the provider for these codes to be assigned. The obesity class codes can be reported with other obesity codes in Chapters 4 and 15 to fully describe the condition. However, if both class 3 obesity and morbid obesity are documented, only a code for class 3 obesity should be assigned as it is more specific.

Checked E66.811 and E66.812 are billable and verified no-HCC-mapping. Class 1 and class 2 are not a path to HCC 48.

Checked E66.813 maps to HCC 48. If the provider documented both class 3 obesity and morbid obesity, the guideline assigns E66.813, not E66.01. That is an ICD-10-CM specificity rule. The V28 category is still HCC 48.

Do not assign E66.813 from a BMI number. Class has to be in the provider documentation.

Some BMI codes map. Most do not.

This is the usual miss on an obesity chart.

Checked Z68.41, Z68.42, Z68.43, Z68.44, and Z68.45 map to HCC 48, CNA 0.186. Checked Z68.56 maps to the same category. Those codes are in the official 2026 Final ICD-10-CM Mappings file and in the official V28 CC file.

Checked Z68.1, Z68.25, Z68.30, Z68.35, Z68.39, Z68.54, and Z68.55 are billable and verified no-HCC-mapping. Adult BMI 30-39 is not HCC 48. Pediatric BMI below 140 percent of the 95th percentile, in the checked set, is not HCC 48.

The payment map and the coding rule are not the same question.

Official Guidelines Section I.C.21.c.3 say BMI codes should only be assigned when there is an associated, reportable diagnosis (such as obesity or anorexia) documented by the patient's provider. Do not assign BMI codes during pregnancy. When the documentation reflects fluctuating BMI values during the current encounter for an associated reportable condition, assign a code for the most severe value.

Official Guidelines Section I.B.14 allow BMI code assignment from clinicians other than the patient's provider, such as a dietitian. The associated diagnosis, such as overweight or obesity, must be documented by the patient's provider. BMI codes should only be reported as secondary diagnoses.

Z68 Tabular notes say adult BMI codes are for persons 20 years of age or older, and pediatric BMI codes are for persons 2-19 years of age, using CDC growth-chart percentiles. The official V28 CC file lists an age edit of age >= 15 on Z68.41 through Z68.45. Z68.56 does not show that age edit in this file. Those are file facts. They do not replace the Tabular age notes.

A BMI of 42 in vital signs, with no provider obesity diagnosis, is not a finished E66 code and is not a finished Z68.41 code. Query or leave the BMI off. Official Guidelines Section I.A.19 say code assignment is based on the provider's diagnostic statement that the condition exists, not on the clinical criteria the provider used to establish it. I.B.14 is the documented exception for the BMI value itself, not for inventing the obesity diagnosis.

Do not skip Z68.41 when the record supports it and an associated reportable diagnosis is present. Home-grown rules that say "BMI codes never map" are wrong for this release. The official V28 file maps the checked adult BMI 40+ codes.

This article does not inventory every Z68.2x leaf code. Look up the documented BMI code.

Historical V24 reference

The current CMS 2026 Final ICD-10-CM Mappings file contains the generic CMS-HCC V28 column. It does not contain a generic CMS-HCC V24 column. HCC Buddy uses the CMS 2025 Midyear/Final ICD-10-CM Mappings file for its historical CMS-HCC V24, payment year 2025 reference. It does not infer a V24 mapping for FY2026 codes that are absent from that historical file.

The V28 map above applies to CY2026 non-PACE payment. Use the official mapping and model for the payment year and program under review. PACE uses a CY2026 blend and cannot be represented by one V28 or V24 mapping and coefficient.

This article does not publish a V24 coefficient in this section, and it does not turn a missing historical row into "no HCC."

Documentation and the query trigger

Official Guidelines Section I.B.2 require diagnosis codes at the highest number of characters available and at the highest specificity documented in the record. The provider, not the coder, establishes the diagnosis. A joint effort between provider and coder is required to get the documentation complete enough to code (guidelines introduction and Section I.B.18).

What that means on an obesity chart:

Query when the record is internally inconsistent or incomplete, not to harvest a coefficient. HCC Buddy educational query language, not a CMS form:

"The assessment lists obesity and a BMI is recorded. Please document whether this is overweight, unspecified obesity, class 1, class 2, class 3, morbid (severe) obesity due to excess calories, morbid obesity with alveolar hypoventilation, or another specified obesity diagnosis, and whether a current BMI code should be reported with that diagnosis."

If the provider cannot specify class or morbid obesity, keep E66.9 when obesity is the documented diagnosis. That is the guideline-compliant answer. It does not map to HCC 48. See provider query templates.

Diabetes and CKD are different maps. Look up the documented E11 or N18 code. See the diabetes HCC coding guide and the CKD HCC coding guide.

Primary sources

Disclaimer

HCC Buddy is not affiliated with, endorsed by, or approved by CMS, CDC, NCHS, AHA, AHIMA, or WHO. This page is original HCC Buddy education for risk-adjustment coders. It does not replace the official classification, the Official Guidelines, payer policy, or coder judgment. Every mapping and coefficient above is scoped to FY2026 period 2 and CMS-HCC V28 payment year 2026 CNA unless a different source is named. Re-check the official file for the date of service in front of you. HCC Buddy does not store PHI.

Written by the HCC Buddy Coding Team.

Frequently Asked Questions

Does E66.9 map to an HCC under V28?

No. E66.9 is billable, and the FY2026 period 2 MCP receipt returns verified no-HCC-mapping. E66.9 is not a row in the official 2026 Final ICD-10-CM Mappings file and is absent from the official V28 CC file. That is a verified no-map, not an incomplete file. E66.811, E66.812, E66.09, and E66.3 have the same V28 result.

Which obesity and BMI codes map to HCC 48?

Checked E66.01, E66.2, E66.813, Z68.41, Z68.42, Z68.43, Z68.44, Z68.45, and Z68.56. The official V28 label is "Morbid Obesity." The CNA coefficient in the PY2026 V28 factor file is 0.186. Other segments differ. Official V28 hierarchy lists no secondary HCC under 48, so those codes do not stack.

Does Z68.41 map even though BMI needs an associated diagnosis?

Yes. Z68.41 is billable and maps to HCC 48 under V28. Official Guidelines Section I.C.21.c.3 still require an associated, reportable diagnosis documented by the patient's provider, and Section I.B.14 still treat BMI as a secondary code that other clinicians may document. The ICD-10-CM assignment rule and the payment map are not the same question. Z68.35 does not map.

If the record says morbid obesity and class 3, which code?

E66.813. Official Guidelines Section I.C.4.b.1 say that if both class 3 obesity and morbid obesity are documented, only a code for class 3 obesity should be assigned because it is more specific. E66.01 has an Excludes1 note for E66.2. Do not assign E66.813 from a BMI value without a documented class.

Why do E66.01 and Z68.41 not both pay a second HCC 48?

Because both map to the same official V28 category, HCC 48, and the official V28 hierarchy file lists no secondary HCC under 48. E66 still has a Use additional note for BMI when it is known. Code both when the record supports both. The payment result is one HCC 48 line.