2027 ICD-10-CM Diagnosis Code E03.5Myxedema coma
ICD-10-CM Codes›E00–E89›E00-E07›E03
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 202
- Chronic Condition
E03.5 is a billable ICD-10-CM diagnosis code for myxedema coma. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 80 through 81, 791, 793. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 718 closely related codes. Coders also document this condition as iatrogenic myxedema coma. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Coma; stupor; and brain damage and Thyroid disorders.
For Medicare Advantage risk adjustment, E03.5 maps to CMS-HCC Category 202 (Coma, Brain Compression/Anoxic Damage) under the V28 model, adding a risk factor of about 0.543 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
E03.5 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.
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.
- Iatrogenic myxedema coma
- Myxedema coma
- Myxedema coma due to subclinical hypothyroidism
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to E03.5: its own notes plus those printed at E03 and Chapter 4. A note printed at a category, block or chapter applies to every code under it.
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Notes
General instructions on how these codes are used.
- All neoplasms, whether functionally active or not, are classified in Chapter 2. Appropriate codes in this chapter (i.e. E05.8, E07.0, E16-E31, E34.-) may be used as additional codes to indicate either functional activity by neoplasms and ectopic endocrine tissue or hyperfunction and hypofunction of endocrine glands associated with neoplasms and other conditions classified elsewhere.
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name E03.5, its category, or a range that includes it.
Applicable To 1
These notes mention E03.5.
- Z83.4 Family history of other endocrine, nutritional and metabolic diseases
Code First 7
These codes say to code first a condition named in the note, and E03.5 is one of the conditions named.
- G13.2 Systemic atrophy primarily affecting the central nervous system in myxedemahypothyroidism (E03.-) names E03.-, which includes this code
- H28 Cataract in diseases classified elsewheremyxedema (E03.-) names E03.-, which includes this code
- D63.8 Anemia in other chronic diseases classified elsewhere
- F02 Dementia in other diseases classified elsewhere
- G32.8 Other specified degenerative disorders of nervous system in diseases classified elsewhere
- G63 Polyneuropathy in diseases classified elsewhere
- M14.8 Arthropathies in other specified diseases classified elsewhere
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
myxedematous E03.5
Myxedema (adult) (idiocy) (infantile) (juvenile) See Also: Hypothyroidism; E03.9
coma E03.5
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Myxedema Coma
a life-threatening condition characterized by altered mental status and defective thermoregulation. it is seen in individuals with severe, decompensated hypothyroidism.
Patient EducationClinical
Coma
A coma is a deep state of unconsciousness. An individual in a coma is alive but unable to move or respond to his or her environment. Coma may occur as a complication of an underlying illness, or as a result of injuries, such as brain injury.
Read the full article at MedlinePlus
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Convert E03.5 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About E03.5Overview
What is the ICD-10 code for myxedema coma?
The ICD-10-CM code for myxedema coma is E03.5 (sometimes written as E035). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is E03.5 (Other hypothyroidism) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report myxedema coma on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does E03.5 group to?
When myxedema coma is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 81, 80, with relative weights from 0.7941 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.
Is E03.5 a CC or MCC?
CMS lists E03.5 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 718 closely related codes in its exclusion list.
Can E03.5 be reported with E89.0?
Not as a rule. The Excludes1 note at E03, which applies to E03.5, lists "postprocedural hypothyroidism (E89.0)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What HCC is E03.5?
E03.5 (myxedema coma) maps to CMS-HCC Category 202 (Coma, Brain Compression/Anoxic Damage), commonly written as HCC 202, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 23 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 44.
Does E03.5 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, E03.5 adds a risk adjustment factor of about 0.543 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.097 to 0.721 depending on the payment segment). A more severe related category (HCC 63, HCC 397, and HCC 398) supersedes it when both are reported. See the full factor table on the HCC 202 category page.
