What Does ICD-10 Code E66.812 Mean?
ICD-10-CM code E66.812 designates a diagnosis of Obesity, Class 2 — a clinically distinct severity classification for adult obesity based on body mass index (BMI). This code became effective October 1, 2024 (FY2025) as part of a significant expansion to the E66.8 subcategory, replacing the imprecise “Other obesity” umbrella that previously left class-level severity undocumented.
Key attributes of E66.812:
- Billable/valid: Yes — active and valid through September 30, 2026 under ICD-10-CM FY2026
- BMI range: 35.0–39.9 kg/m² (adults); BMI class must be supported by a separately reported Z68 code
- Setting applicability: Outpatient, inpatient, and professional fee claims
- Questionable admission diagnosis: Yes — E66.812 alone is generally insufficient to justify acute inpatient admission
What Conditions Does E66.812 Cover — and What Does It Exclude?
E66.812 is used when a provider documents Class 2 obesity specifically. The code captures the clinical presentation of significant excess adiposity that carries elevated risk for metabolic, cardiovascular, and musculoskeletal comorbidities.
Clinical presentations and scenarios covered include:
- Adult patient with documented Class 2 obesity and BMI between 35.0 and 39.9
- Obesity classified as “Class II” by the treating provider in clinical notes
- Class 2 obesity documented as an active comorbidity affecting management of another condition (e.g., sleep apnea, type 2 diabetes, hypertension)
- Class 2 obesity in a patient not otherwise meeting criteria for morbid obesity (E66.01)
What Does E66.812 Specifically Exclude?
The E66 category carries several important exclusion conventions coders must apply:
- Excludes 1 (cannot be coded together): Adiposogenital dystrophy (E23.6); lipomatosis NOS (E88.2); lipomatosis dolorosa (E88.2); Prader-Willi syndrome (Q87.11)
- Excludes 2 (may be coded together when both are present): Obesity complicating pregnancy, childbirth, and the puerperium — but only if coded with the obstetric code as the primary diagnosis (O99.21-)
- Not included: Drug-induced obesity (E66.1); severe obesity with alveolar hypoventilation (E66.2); obesity due to excess calories only, when documented as such (which may direct coders toward E66.01 or E66.09 under query)
When Is E66.812 the Right Code to Use?
E66.812 is appropriate when documentation specifically supports Class 2 obesity classification. Follow these steps before assigning the code:
- Confirm provider documentation explicitly states “Class 2 obesity” or “Class II obesity.” BMI alone is not sufficient — the provider or a qualified clinician must document the class designation.
- Verify BMI is within the 35.0–39.9 range. Per AHA Coding Clinic Q4 2024, BMI ranges are an authoritative reference for class assignment even though they do not appear in the code descriptor itself.
- Determine whether the obesity is attributed to a specific etiology. If the provider documents “obesity due to excess calories, Class 2,” some payers and CDI advisors argue E66.01 (morbid obesity due to excess calories) may also apply — a point of active controversy (see FAQ section).
- Check for pregnancy. If the patient is pregnant, sequence the obstetric obesity code (O99.21-) first; E66.812 follows as an additional code.
- Assign the appropriate Z68 code to capture the specific BMI (e.g., Z68.35 for BMI 35.0–35.9, continuing through Z68.39 for BMI 39.0–39.9).
- Assess comorbidities that may require additional codes (e.g., E11.9 for type 2 diabetes, I10 for hypertension, G47.33 for obstructive sleep apnea).
How Does E66.812 Differ From E66.01 (Morbid Obesity Due to Excess Calories)?
This is the most common point of confusion in the post-FY2025 coding landscape. In practice, queries to CDI teams about E66.812 vs. E66.01 have become one of the most frequent clarification requests since October 2024.
| Feature | E66.812 | E66.01 |
|---|---|---|
| Code description | Obesity, Class 2 | Morbid (severe) obesity due to excess calories |
| BMI implication | 35.0–39.9 (per Coding Clinic Q4 2024) | Typically ≥35 with comorbidities, or ≥40 |
| Etiology required | No — class designation alone | Yes — “due to excess calories” must be documented |
| Effective date | New October 1, 2024 | Long-standing legacy code |
| Excludes1 relationship | No Excludes1 note between these codes | No Excludes1 note between these codes |
| Best practice | Use when provider documents “Class 2 obesity” | Use when provider documents morbid/severe obesity due to excess calories |
| Dual coding | Actively debated; Coding Clinic Q4 2024 guidance pending further clarification | May coexist with E66.812 in some clinical scenarios |
In practice: Auditors frequently flag encounters where both E66.812 and E66.01 are submitted together without clear documentation justifying dual assignment. Until definitive Coding Clinic guidance is issued, code based strictly on what the provider documented — and query if the documentation supports both.
What Documentation Is Required to Support E66.812?
What Must the Provider Document in the Clinical Notes?
Documentation must meet these requirements before E66.812 can be assigned:
- Explicit class designation — the term “Class 2,” “Class II,” or an equivalent clinically accepted term must appear in the provider’s note, problem list, or assessment
- Provider identity — documentation must come from a licensed treating provider (MD, DO, NP, PA); coder-inferred class from BMI alone is not sufficient
- Active diagnosis status — the condition must be documented as an active, current diagnosis affecting care during the encounter, not merely historical
- Comorbidity linkage (when applicable) — if obesity is impacting management of another condition (e.g., joint pain, diabetes), the clinical note should reflect this connection to support medical necessity
- BMI recorded by a qualified clinician — per ICD-10-CM guidelines, BMI may be documented by clinicians other than the treating provider (e.g., nursing staff) and is still reportable
Which Diagnostic or Lab Results Support This Code?
While no lab test “confirms” a class of obesity, the following findings commonly appear in documentation and support E66.812 assignment:
- BMI calculation in the 35.0–39.9 range, documented in the visit record
- Anthropometric measurements (height, weight) recorded during the encounter
- Metabolic panel results showing obesity-related complications (elevated lipids, fasting glucose) that reinforce clinical management of obesity
- Polysomnography results if obesity hypoventilation or sleep apnea is a concurrent diagnosis
- Dietary or bariatric consultation notes documenting Class 2 obesity classification
What Is the Documentation Standard for Inpatient vs. Outpatient Settings?
| Setting | Documentation Standard |
|---|---|
| Outpatient | Code the condition to the highest degree of certainty documented at the visit; provider must explicitly state Class 2 obesity |
| Inpatient | Query the provider if obesity class is not documented but BMI and clinical indicators suggest Class 2; coding from BMI alone without provider documentation remains a compliance risk |
| Obstetric inpatient | Sequence O99.21- first; E66.812 as additional; obstetric record must document obesity impacting pregnancy management |
How Does E66.812 Affect Medical Billing and Claims?
E66.812 is a billable diagnosis code valid for HIPAA-covered claim submissions. Its impact on reimbursement is primarily indirect — the code supports medical necessity for related services rather than triggering a specific payment itself. Key billing considerations:
- E66.812 strengthens medical necessity for intensive behavioral therapy (IBT) for obesity under Medicare (covered when BMI ≥30, with primary care provider performing the service)
- The code supports coverage justification for anti-obesity medications (AOMs) such as GLP-1 receptor agonists when payer policies require documented obesity class
- MS-DRG grouping: E66.812 maps to DRG 640 (with MCC) or DRG 641 (without MCC) when used in inpatient settings
- Payers increasingly require specific obesity class documentation to authorize bariatric surgery (typically Class 2 with comorbidities, or Class 3)
- Always pair E66.812 with the appropriate Z68 BMI code — omitting the Z68 code is a frequent audit finding
What CPT or Procedure Codes Are Commonly Billed With E66.812?
| CPT Code | Description | Pairing Context |
|---|---|---|
| 99213–99215 | Office/outpatient E&M visit | Primary care obesity management visit |
| G0447 | IBT for obesity, individual (15 min) | Medicare-covered behavioral counseling |
| G0473 | IBT for obesity, group (30 min) | Medicare group behavioral session |
| 43770–43775 | Laparoscopic bariatric procedures | Surgical intervention for Class 2 obesity with comorbidities |
| 97802–97804 | Medical nutrition therapy | Dietitian services for obesity management |
| 99401–99404 | Preventive counseling | Lifestyle modification counseling |
Are There Any Prior Authorization or Coverage Restrictions?
- Medicare IBT: Covered for BMI ≥30 in primary care settings; E66.812 supports this threshold — no prior auth typically required for initial sessions
- Bariatric surgery: Most commercial payers require BMI ≥35 with at least one obesity-related comorbidity for Class 2 patients; prior authorization is almost universally required
- Anti-obesity medications: Coverage varies widely by payer; many commercial plans and Medicare Part D have historically excluded AOMs, though this is evolving in 2025–2026
- LCD considerations: Review applicable Local Coverage Determinations for bariatric surgery and intensive outpatient programs, as E66.812 is a relatively new code that some LCDs may not yet reference by number
What Coding Errors Should You Avoid With E66.812?
Since E66.812 was introduced in FY2025, auditors and CDI specialists have already identified recurring patterns of miscoding. The most common errors, ranked by audit frequency:
- Assigning E66.812 based on BMI alone — a coder calculating the class from documented height and weight without explicit provider class documentation is a compliance violation; always require provider-level documentation
- Omitting the Z68 BMI code — ICD-10-CM instructs “use additional code” for BMI; submitting E66.812 without a Z68.3x code leaves clinical detail on the table and may trigger edits
- Using E66.812 and E66.9 together — E66.9 (obesity, unspecified) should never be reported alongside E66.812 on the same claim; the more specific code replaces the unspecified code
- Incorrect sequencing in obstetric cases — sequencing E66.812 before O99.21- in pregnancy-related encounters violates the “code first” convention
- Conflating E66.812 with E66.01 without documentation support — dual coding these two requires clear documentation justifying both; absent that, pick the code that best matches the provider’s own language
- Treating E66.812 as a principal inpatient diagnosis — this code is flagged as a questionable admission diagnosis; if listed as principal without a supporting primary condition, expect a denial
What Do Auditors Look for When Reviewing Claims With E66.812?
- Presence of explicit “Class 2” or “Class II” language from a treating provider in the medical record
- Matching BMI documentation in the 35.0–39.9 range in the clinical notes
- Appropriate Z68 code reported alongside E66.812
- No duplicate reporting of E66.812 + E66.9 on the same claim
- Correct sequencing in obstetric or complication-driven encounters
- Medical necessity linkage — that obesity is documented as affecting the care provided at the visit
How Does E66.812 Relate to Other ICD-10 Codes?
Understanding E66.812’s position within the broader E66 family is essential for diagnosis code specificity and accurate claim submission.
| Code | Description | Relationship to E66.812 | Key Distinction |
|---|---|---|---|
| E66.811 | Obesity, Class 1 | Sibling code | BMI 30.0–34.9; less severe |
| E66.813 | Obesity, Class 3 | Sibling code | BMI ≥40; most severe classification |
| E66.01 | Morbid obesity due to excess calories | Related; not mutually exclusive per current guidelines | Requires etiology documentation; active dual-coding controversy |
| E66.09 | Other obesity due to excess calories | Related | Excess calorie etiology documented; less severe than E66.01 |
| E66.1 | Drug-induced obesity | Distinct etiology | Medication must be documented as causative; use additional code for adverse effect |
| E66.2 | Severe obesity with alveolar hypoventilation | Complication-based | BMI often overlaps Class 2–3; requires documented hypoventilation |
| E66.9 | Obesity, unspecified | Less specific; do not combine | Use only when class is entirely undocumented and cannot be queried |
| Z68.35–Z68.39 | BMI 35.0–39.9 (adult) | Required companion codes | Specific BMI must be reported alongside E66.812 |
What Is the Correct Code Sequencing When E66.812 Appears With Other Diagnoses?
- Obstetric encounters: Sequence O99.21- (obesity complicating pregnancy/childbirth/puerperium) first, then E66.812, then the Z68 BMI code
- Surgical or procedural encounters for obesity: E66.812 may serve as the primary outpatient diagnosis when the procedure is specifically for obesity management (e.g., bariatric surgery); confirm with operative documentation
- Encounters where obesity is a comorbidity: Sequence the condition being treated (e.g., E11.9 type 2 diabetes) first; list E66.812 and the Z68 code as additional diagnoses
- Drug-induced obesity: If obesity is medication-induced, E66.1 takes precedence; E66.812 should not be simultaneously assigned for the same obesity episode
- Etiology/manifestation pairs: When obesity-linked conditions have mandatory sequencing rules (e.g., obesity hypoventilation — E66.2), follow the “code first” instruction in the tabular
Real-World Coding Scenario — How E66.812 Is Applied in Practice
Scenario: A 48-year-old female presents to her primary care physician for a routine follow-up for type 2 diabetes and hypertension. During the visit, the provider documents “the patient has Class 2 obesity with a BMI of 37.4 and we discussed initiating GLP-1 therapy.” The nurse records the BMI in the vitals. The provider’s assessment lists: Type 2 diabetes mellitus without complications; essential hypertension; Class 2 obesity.
Correct Code Application
- E11.9 — Type 2 diabetes mellitus without complications (principal/first-listed; primary reason for visit)
- I10 — Essential (primary) hypertension (active comorbidity)
- E66.812 — Obesity, Class 2 (documented by provider in assessment)
- Z68.37 — BMI 37.0–37.9, adult (matching the documented 37.4 BMI)
Common Mistake in This Scenario
- Incorrect: Assigning E66.9 (obesity, unspecified) because the coder did not notice the “Class 2” language in the assessment — or assigning E66.01 because the provider mentioned “severe” health risks associated with the obesity without using the term “morbid”
- Why it fails: E66.9 is a nonspecific code inappropriate when class is documented. E66.01 requires documentation of “morbid,” “severe,” or “excess calories” as the etiology — the word “Class 2” alone does not trigger that code per current Coding Clinic guidance
Frequently Asked Questions About ICD-10 Code E66.812
Is ICD-10 Code E66.812 Valid for Use in 2025 and 2026?
ICD-10-CM code E66.812 is valid and billable for claims with dates of service from October 1, 2024 through September 30, 2026, making it active for both FY2025 and FY2026. The code was newly created effective October 1, 2024 as part of the FY2025 ICD-10-CM update and has not been revised or inactivated since its introduction.
What BMI Range Does E66.812 Cover?
E66.812 corresponds to a BMI of 35.0–39.9 in adults, as established by AHA Coding Clinic Q4 2024, which provided BMI ranges as an authoritative reference for the new class-based obesity codes. Note that the BMI range does not appear in the code description itself — coders must reference Coding Clinic guidance and pair E66.812 with the appropriate Z68.3x BMI code.
What Is the Difference Between E66.812 and E66.01?
E66.812 designates obesity classified by the provider as “Class 2” without requiring documentation of a specific etiology, while E66.01 designates morbid obesity specifically due to excess calories and requires that the provider document that causal link. These codes currently have no Excludes1 relationship, meaning dual coding is technically not prohibited — but auditors and CDI advisors recommend assigning only the code that most precisely matches the provider’s documentation and querying when the record supports both.
Can E66.812 Be Used as a Principal Inpatient Diagnosis?
E66.812 is designated a “questionable admission diagnosis” in the ICD-10-CM tabular, meaning it should not typically stand alone as the principal diagnosis for an acute inpatient admission. In inpatient settings, E66.812 functions most appropriately as a secondary diagnosis supporting management of a primary admitting condition such as a cardiac event, surgical procedure, or metabolic emergency.
Do I Always Need to Add a Z68 Code When Using E66.812?
Yes. The ICD-10-CM tabular includes a “use additional code” instruction at the E66 category level directing coders to report BMI using Z68.1–Z68.45 for adults (or Z68.5x for pediatric patients) when the BMI is known. Omitting the Z68 code is one of the most frequently identified deficiencies in coding audit preparation reviews and can result in claim edits or documentation queries.
How Should E66.812 Be Coded in Pregnant Patients?
When a pregnant patient has Class 2 obesity, coders must sequence the obstetric diagnosis first. The correct sequencing places an O99.21- code (obesity complicating pregnancy, childbirth, or the puerperium — with the appropriate fifth character for trimester or postpartum) as the primary code, followed by E66.812 and the Z68 BMI code. This “code first” convention is explicitly noted in the ICD-10-CM tabular under E66.812.
Is E66.812 Covered by Medicare for Obesity Counseling Services?
E66.812 can support Medicare coverage for Intensive Behavioral Therapy (IBT) for obesity under the Medicare preventive benefit, which covers patients with a BMI ≥30 receiving counseling in a primary care setting. Class 2 obesity (BMI 35.0–39.9) clearly meets this threshold. However, Medicare’s IBT benefit requires the service to be furnished by a primary care physician or qualified primary care practitioner, and the diagnosis must be the focus of the visit — not merely an incidental comorbidity.
Key Takeaways
- E66.812 is a billable ICD-10-CM code for Obesity, Class 2, effective October 1, 2024, covering adults with a BMI of 35.0–39.9 when the provider explicitly documents the class designation
- Provider documentation of the class — not coder-inferred BMI calculation — is required for valid assignment; this is the single most common compliance failure with this code
- Always pair E66.812 with a Z68.3x BMI code; omitting the BMI code is a documented audit finding across revenue cycle compliance reviews
- E66.812 vs. E66.01 remains an active area of coding controversy; follow the provider’s language precisely and consider a CDI query when documentation supports both
- Obstetric sequencing is mandatory: O99.21- precedes E66.812 when obesity complicates pregnancy or the puerperium
- E66.812 is a questionable admission diagnosis — it should not serve as the sole principal inpatient diagnosis
- For the most current guidance, coders should consult the ICD-10-CM Official Coding Guidelines released annually by CMS and monitor AHA Coding Clinic for evolving advisory opinions on the FY2025 obesity code restructuring
For additional coding guidance, refer to the CMS ICD-10-CM official code files and guidelines, the CDC obesity code implementation resources, and quarterly releases from the AHA Coding Clinic for authoritative advisory opinions.