E03.5
BillableMyxedema coma
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is E03.5 an HCC code?
Yes. E03.5 maps to Coma, Brain Compression/Anoxic Damage under the CMS-HCC V28 risk adjustment model (and Other Significant Endocrine and Metabolic Disorders under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for E03.5
For E03.5 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- 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
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed E03.5 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
E03.5 is the ICD-10-CM diagnosis code for myxedema coma. A life-threatening emergency condition where severe hypothyroidism causes a coma-like state with dangerously low body temperature, heart rate, and blood pressure. E03.5 sits in the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89), within the section covering disorders of thyroid gland (e00-e07).
Under the CMS-HCC V28 risk adjustment model, E03.5 maps to Coma, Brain Compression/Anoxic Damage (HCC 202) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, E03.5 maps to Other Significant Endocrine and Metabolic Disorders (HCC 23) with a community, non-dual, aged base RAF weight of 0.230. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
This is a medical emergency requiring ICU-level care; always code with appropriate severity indicators and comorbidities. Because E03.5 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. 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, RAF weights, and MEAT documentation criteria for E03.5 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a medical emergency requiring ICU-level care; always code with appropriate severity indicators and comorbidities
- •Document precipitating factors (infection, medication non-compliance, cold exposure) as these are critical for treatment decisions
Clinical Significance
Myxedema coma is a life-threatening endocrine emergency representing the most severe form of hypothyroidism, characterized by profound hypothermia, altered mental status progressing to coma, cardiovascular collapse, hypoventilation, and multiorgan dysfunction. Despite the name, true coma may not be present; severe obtundation or lethargy qualifies. Mortality rates range from 20-60% even with aggressive treatment, making rapid recognition and intravenous thyroid hormone replacement critical.
Documentation Requirements
- ✓Documentation must clearly establish myxedema coma or crisis with clinical findings including altered mental status, hypothermia, bradycardia, hypotension, and hypoventilation.
- ✓Severely deranged thyroid function tests (profoundly elevated thyroid-stimulating hormone, very low or undetectable free thyroxine) must be documented.
- ✓The precipitating factor (infection, medication non-adherence, cold exposure, surgery) should be identified.
- ✓Treatment with intravenous levothyroxine and/or liothyronine, stress-dose hydrocortisone, and intensive care management should be recorded.