E05.21
BillableThyrotoxicosis with toxic multinodular goiter with thyrotoxic crisis or storm
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is E05.21 an HCC code?
No. E05.21 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
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 E05.21
For E05.21to 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 E05.21 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
E05.21 is the ICD-10-CM diagnosis code for thyrotoxicosis with toxic multinodular goiter with thyrotoxic crisis or storm. Overactive thyroid caused by multiple nodules producing excess hormone, with thyroid storm (a severe, life-threatening condition). E05.21 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).
E05.21 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
This code does not map to any HCC under V24 or V28, providing no community risk adjustment impact. It maps to RxHCC 44 (Osteoporosis, Vertebral and Pathological Fractures). Despite being a critical care diagnosis with high mortality risk, thyroid storm from multinodular goiter does not carry community model risk adjustment weight, though associated comorbidities may have their own HCC mappings.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for E05.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code requires documentation of both multinodular goiter AND thyrotoxic crisis or storm
- •Thyroid storm is a medical emergency; ensure appropriate severity coding and critical care documentation
Clinical Significance
Thyrotoxicosis with toxic multinodular goiter with thyrotoxic crisis or storm is an acute, life-threatening complication in patients with toxic multinodular goiter. This presentation tends to occur in older patients who may have significant cardiovascular comorbidities, making management particularly challenging. The combination of thyroid storm physiology and age-related cardiovascular vulnerability results in high mortality risk from cardiac arrhythmias, heart failure, and cardiovascular collapse.
Documentation Requirements
- ✓Documentation must establish both the toxic multinodular goiter etiology and thyrotoxic crisis meeting clinical diagnostic criteria (Burch-Wartofsky Point Scale greater than 45).
- ✓Imaging confirming multinodular goiter, thyroid function tests, clinical findings of storm (hyperthermia, severe tachycardia, altered mental status), precipitating factors, and intensive care treatment including antithyroid drugs, beta-blockers, corticosteroids, and supportive care should be documented.
Commonly Confused Codes
- •E05.20 (Thyrotoxicosis with toxic multinodular goiter WITHOUT crisis) captures the stable form.
- •E05.01 (Thyrotoxicosis with diffuse goiter with crisis) captures storm from Graves disease.
- •E05.11 (Thyrotoxicosis with toxic single thyroid nodule with crisis) captures storm from a single toxic nodule.
- •E05.91 (Thyrotoxicosis, unspecified with crisis) is less specific and should not be used when the multinodular etiology is documented.