What is ICD-10 code E05.81?

E05.81 is the ICD-10-CM diagnosis code for Other thyrotoxicosis with thyrotoxic crisis or storm. Overactive thyroid from other specified causes, with thyroid storm (severe, life-threatening condition). It belongs to the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89). E05.81 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. E05.81 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. E05.81 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. E05.81 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for E05.81?

E05.81 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards E05.81 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

What should coders know when reporting E05.81?

Use this code only when the cause of thyrotoxicosis doesn't fit other E05 categories Document the specific cause in the medical record for clarity and future reference

E05.81: Other thyrotoxicosis with thyrotoxic

ICD-10-CM Code View

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Code lookupE05.81Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Endocrine, nutritional and metabolic diseases (E00-E89) / Disorders of thyroid gland (E00-E07)

E05.81

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Other thyrotoxicosis with thyrotoxic crisis or storm

Overactive thyroid from other specified causes, with thyroid storm (severe, life-threatening condition).

Buddy Insight

CMS-HCC V28

Not risk-adjusted for this model/period.

RAF 0

CMS-HCC V24

Not risk-adjusted for this model/period.

RAF 0

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Not risk-adjusted for this model/period.

RAF 0

RXHCC

Mapped

HCC 44

Thyroid and Parathyroid Disor...

RAF 0.0

Code Trumping

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Code Book Path

Official

E05Thyrotoxicosis [hyperthyroidism]

E05.8Other thyrotoxicosis

E05.81Other thyrotoxicosis with thyrotoxic crisis or storm

Inclusion Terms

Official

Overproduction of thyroid-stimulating hormone

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for E05.81 in this effective period.

Related Child Codes

Official

E05.80Other thyrotoxicosis without thyrotoxic crisis or storm

Includes

Official

ICD-10-CM does not list Includes notes for E05.81 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for E05.81 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for E05.81 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for E05.81 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for E05.81 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Document the specific underlying cause of thyrotoxicosis, clinical criteria confirming thyrotoxic crisis (hyperpyrexia, cardiovascular instability, neurological changes), and the critical care interventions administered.

Include the precipitating factor for storm if identifiable, and record the specific rare etiology driving the condition.

MEAT Support

HCC Buddy guidance

Include the precipitating factor for storm if identifiable, and record the specific rare etiology driving the condition.

Audit Caution

HCC Buddy guidance

The 'other' category requires that the provider has identified a specific etiology that does not fall into the preceding E05 subcategories.

If the etiology is unknown, use E05.91 instead.

The crisis component must be explicitly documented as thyroid storm or thyrotoxic crisis.

Common Mistakes

HCC Buddy guidance

E05.80: Other thyrotoxicosis WITHOUT crisis — use when storm criteria are not met

E05.91: Thyrotoxicosis unspecified with crisis — use only when the underlying cause cannot be determined

E05.01: Thyrotoxicosis with diffuse goiter with crisis — use when Graves disease is the cause

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is E05.81 an HCC code?

No. E05.81 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.

HCC Category Mapping

RxHCCHCC 44, Thyroid and Parathyroid Disorders

0.000

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 E05.81

For E05.81to 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 E05.81 during that encounter, not just copy-forwarded from a problem list.

What This Code Means

E05.81 is the ICD-10-CM diagnosis code for other thyrotoxicosis with thyrotoxic crisis or storm. Overactive thyroid from other specified causes, with thyroid storm (severe, life-threatening condition). E05.81 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).

E05.81 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.

Maps to RxHCC 44 (Osteoporosis, Vertebral and Pathological Fractures) in the prescription drug model. Despite representing a critical care scenario, this code does not map to CMS-HCC v28 or v24 models. The RxHCC mapping reflects the high prescription drug utilization for thyroid storm management.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for E05.81 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use this code only when the cause of thyrotoxicosis doesn't fit other E05 categories
•Document the specific cause in the medical record for clarity and future reference

Clinical Significance

Other thyrotoxicosis with thyrotoxic crisis represents thyroid storm arising from uncommon etiologies such as TSH-secreting pituitary adenomas, gestational thyrotoxicosis, or drug-induced hyperthyroidism that has progressed to systemic decompensation. The rare etiology combined with storm physiology creates significant diagnostic and management complexity. Mortality is high without prompt recognition and aggressive multi-modal treatment.

Documentation Requirements

✓Document the specific underlying cause of thyrotoxicosis, clinical criteria confirming thyrotoxic crisis (hyperpyrexia, cardiovascular instability, neurological changes), and the critical care interventions administered.
✓Include the precipitating factor for storm if identifiable, and record the specific rare etiology driving the condition.

Commonly Confused Codes

•E05.80: Other thyrotoxicosis WITHOUT crisis: use when storm criteria are not met
•E05.91: Thyrotoxicosis unspecified with crisis: use only when the underlying cause cannot be determined
•E05.01: Thyrotoxicosis with diffuse goiter with crisis: use when Graves disease is the cause

Child Codes

E05.80Other thyrotoxicosis without thyrotoxic crisis or storm

E05.81Other thyrotoxicosis with thyrotoxic crisis or storm

Code Hierarchy

└E05Thyrotoxicosis [hyperthyroidism]└E05.8Other thyrotoxicosis └E05.81Other thyrotoxicosis with thyrotoxic crisis or storm

└E05.81Other thyrotoxicosis with thyrotoxic crisis or storm

E05.81 ICD-10-CM Code: Other thyrotoxicosis with thyrotoxic crisis or storm

HCC Buddy Code Card

E05.81

Is E05.81 an HCC code?

HCC Category Mapping

MEAT Criteria for E05.81

What This Code Means

Coding Tips

Clinical Significance

Documentation Requirements

Commonly Confused Codes

Child Codes

Code Hierarchy

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