What is ICD-10 code E06.4?

E06.4 is the ICD-10-CM diagnosis code for Drug-induced thyroiditis. Thyroid inflammation caused by medications or drugs, which may resolve after discontinuation of the offending agent. It belongs to the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89). E06.4 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. E06.4 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. E06.4 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. E06.4 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 E06.4?

E06.4 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 E06.4 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 E06.4?

Always document the specific drug or medication causing the thyroiditis in the medical record Common culprits include amiodarone, lithium, interferon, and checkpoint inhibitors

E06.4 ICD-10 Code: Drug-induced thyroiditis

ICD-10-CM Code View

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Code lookupE06.4Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

E06.4

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

Drug-induced thyroiditis

Thyroid inflammation caused by medications or drugs, which may resolve after discontinuation of the offending agent.

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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Compare selected patient codes to show trumped or trumps impact.

Code Book Path

Official

E06Thyroiditis

E06.4Drug-induced thyroiditis

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for E06.4 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for E06.4 in this effective period.

Related Child Codes

Official

E06.0Acute thyroiditis

E06.1Subacute thyroiditis

E06.2Chronic thyroiditis with transient thyrotoxicosis

E06.3Autoimmune thyroiditis

E06.5Other chronic thyroiditis

Includes

Official

ICD-10-CM does not list Includes notes for E06.4 in this effective period.

Excludes 1

Official

postpartum thyroiditis (O90.5)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for E06.4 in this effective period.

Use Additional

Official

code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)

Code Also

Official

ICD-10-CM does not list Code Also instructions for E06.4 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Document the specific causative medication, the temporal relationship between drug initiation and thyroiditis onset, thyroid function tests, and whether the manifestation is thyrotoxic or hypothyroid.

Record whether the offending medication can be discontinued or must be continued with thyroid management, and assign an additional adverse effect code for the responsible drug.

MEAT Support

HCC Buddy guidance

Record whether the offending medication can be discontinued or must be continued with thyroid management, and assign an additional adverse effect code for the responsible drug.

Audit Caution

HCC Buddy guidance

Always assign an additional code to identify the causative drug (T36-T50 with 5th character 5 for adverse effect).

Do not overlook checkpoint inhibitor-induced thyroiditis, which is increasingly common in oncology patients.

If the drug causes permanent thyroid damage, transition to the appropriate hypothyroidism code for subsequent encounters.

Common Mistakes

HCC Buddy guidance

E06.0: Acute thyroiditis — infectious etiology, not drug-induced

E06.1: Subacute thyroiditis — viral etiology, although clinical presentation may overlap

E06.3: Autoimmune thyroiditis — may coexist with drug-induced thyroiditis from checkpoint inhibitors

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 E06.4 an HCC code?

No. E06.4 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 E06.4

For E06.4to 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 E06.4 during that encounter, not just copy-forwarded from a problem list.

What This Code Means

E06.4 is the ICD-10-CM diagnosis code for drug-induced thyroiditis. Thyroid inflammation caused by medications or drugs, which may resolve after discontinuation of the offending agent. E06.4 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).

E06.4 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. This code does not map to CMS-HCC v28 or v24 models. The RxHCC mapping captures the drug-related costs of managing both the thyroiditis and potential thyroid replacement therapy.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for E06.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Always document the specific drug or medication causing the thyroiditis in the medical record
•Common culprits include amiodarone, lithium, interferon, and checkpoint inhibitors

Clinical Significance

Drug-induced thyroiditis is an inflammatory thyroid condition caused by medications, most commonly amiodarone, lithium, interferon-alpha, immune checkpoint inhibitors (nivolumab, pembrolizumab), and tyrosine kinase inhibitors. The condition can manifest as either destructive thyroiditis with transient thyrotoxicosis or as direct inhibition of thyroid hormone synthesis causing hypothyroidism. Recognition is critical because management depends on both the type of thyroiditis and the necessity of continuing the causative medication.

Documentation Requirements

✓Document the specific causative medication, the temporal relationship between drug initiation and thyroiditis onset, thyroid function tests, and whether the manifestation is thyrotoxic or hypothyroid.
✓Record whether the offending medication can be discontinued or must be continued with thyroid management, and assign an additional adverse effect code for the responsible drug.

Use Additional Code

code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)

Commonly Confused Codes

•E06.0: Acute thyroiditis — infectious etiology, not drug-induced
•E06.1: Subacute thyroiditis — viral etiology, although clinical presentation may overlap
•E06.3: Autoimmune thyroiditis — may coexist with drug-induced thyroiditis from checkpoint inhibitors