ICD-10 E66.01
Billable / Specific HCC v28: 22Morbid (severe) obesity due to excess calories
About ICD-10-CM E66.01
ICD-10-CM code E66.01 represents Morbid (severe) obesity due to excess calories. This is a billable/specific code in the Endocrine, Nutritional, and Metabolic chapter (block E66). The 2026 edition of ICD-10-CM E66.01 became effective on October 1, 2025.
Coding Tips for E66.01
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
E66.01 is a CMS-HCC v28 risk-adjustment code (category 22). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
Type 1 Excludes
Pure excludes, these codes can never be coded together with E66.01. The conditions are mutually exclusive (e.g., congenital vs acquired forms).
- morbid (severe) obesity with alveolar hypoventilation (E66.2)
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Medicare LCD Coverage for E66.01
Local Coverage Determinations (LCDs) from CMS MACs that list E66.01 as a covered diagnosis.
Showing top 10 of 180 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing E66.01.
5 Aetna
3 Cigna
5 Medicare
CPT Codes Commonly Billed with E66.01
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 99204 New patient office visit — multiple chronic conditions: HTN, T2DM, hyperlipidemia, asthma, anxiety, depression, obesity, IBS, COPD, thyroid, anemia, CAD, sleep apnea, psoriasis, RA Primary Care
- 99205 New patient office visit — complex/high-risk: uncontrolled diabetes, heart failure, COPD exacerbation, cancer, MS, RA, CKD, CAD, recurrent depression, epilepsy, lupus, syncope, cognitive decline Primary Care
- 99213 Established patient — HTN follow-up, diabetes management, hyperlipidemia, asthma, anxiety, common complaints, back pain, GERD, migraine, acne, joint pain, prediabetes, obesity, anemia, hypothyroid, fatigue Primary Care
- 99214 Established patient — moderate complexity: uncontrolled HTN, diabetes with complications, multiple chronic conditions, COPD, AFib, CKD, sleep apnea, chronic pain, depression Primary Care
- 99215 Established patient — high complexity: HF exacerbation, COPD exacerbation, cancer management, MS, advanced CKD, uncontrolled diabetes, recurrent syncope, respiratory failure, liver cirrhosis Primary Care
- 80061 Lipid panel — hyperlipidemia, hypercholesterolemia, hypertriglyceridemia, CAD, HTN, diabetes, lipid screening, family hx heart disease, obesity Laboratory
- 90865 CMS LCD: Billing and Coding: Psychiatric Codes CMS LCD
- 90889 CMS LCD: Billing and Coding: Psychiatric Codes CMS LCD
- G0451 CMS LCD: Billing and Coding: Psychiatric Codes CMS LCD
- 90880 CMS LCD: Billing and Coding: Psychiatric Codes CMS LCD
Convert E66.01 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| E66.01 | 27801 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To E66.01
Other codes in section E65-E68 (Overweight, obesity and other hyperalimentation).
ICD-10 E66.01, Billing FAQ
Is ICD-10 code E66.01 billable? +
Yes, E66.01 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What codes are Type 1 Excludes for E66.01? +
Type 1 Excludes (never code together with E66.01): morbid (severe) obesity with alveolar hypoventilation (E66.2)
Does E66.01 affect Medicare Advantage HCC risk adjustment? +
Yes. E66.01 maps to CMS-HCC v28 category 22. Capture this diagnosis annually for accurate Medicare Advantage risk score.
What CPT codes are commonly billed with E66.01? +
Procedures frequently paired with E66.01 include: 99204, 99205, 99213, 99214, 99215.
What ICD-9 codes does E66.01 map to? +
Per CMS GEMs, E66.01 maps to ICD-9 codes: 27801. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on July 16, 2026.
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