What is ICD-10 code E01.1?

E01.1 is the ICD-10-CM diagnosis code for Iodine-deficiency related multinodular (endemic) goiter. An enlarged thyroid gland with multiple nodules that develops in areas with low iodine in the diet, where the thyroid develops lumps rather than enlarging uniformly. E01.1 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. E01.1 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. E01.1 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. E01.1 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 E01.1?

E01.1 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 community model rewards E01.1 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's V28/V24 community RAF score in either version. It does, however, map under the Part D RxHCC model (Thyroid and Parathyroid Disorders), which affects the ESRD and/or Part D (RxHCC) risk scores. Coders should check whether provider documentation supports a more specific child code that does map to a community payment HCC.

What should coders know when reporting E01.1?

Confirm the presence of multiple nodules through imaging or clinical documentation to differentiate from diffuse goiter Document any functional status of nodules (toxic vs. non-toxic) if available

2026 ICD-10-CM E01.1: Iodine-deficiency related multinodular

ICD-10-CM Code View

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Code lookupE01.1Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

E01.1

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

Iodine-deficiency related multinodular (endemic) goiter

An enlarged thyroid gland with multiple nodules that develops in areas with low iodine in the diet, where the thyroid develops lumps rather than enlarging uniformly.

Buddy Insight

Iodine-deficiency related multinodular (endemic) goiter represents the progression of chronic iodine deficiency to a thyroid gland with multiple autonomous nodules.

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

N/A

—

Not risk-adjusted for this model/period.

Not mapped

RXHCC

Mapped

HCC 44

Thyroid and Parathyroid Disor...

RAF 0.070

Code Book Path

Official

E01Iodine-deficiency related thyroid disorders and allied conditions

E01.1Iodine-deficiency related multinodular (endemic) goiter

Inclusion Terms

Official

Iodine-deficiency related nodular goiter

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for E01.1 in this effective period.

Related Child Codes

Official

E01.0Iodine-deficiency related diffuse (endemic) goiter

E01.2Iodine-deficiency related (endemic) goiter, unspecified

E01.8Other iodine-deficiency related thyroid disorders and allied conditions

Includes

Official

ICD-10-CM does not list Includes notes for E01.1 in this effective period.

Excludes 1

Official

congenital iodine-deficiency syndrome (E00.-)
subclinical iodine-deficiency hypothyroidism (E02)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for E01.1 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for E01.1 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for E01.1 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation should confirm multinodular thyroid enlargement attributed to iodine deficiency, with imaging (thyroid ultrasound) demonstrating multiple nodules.

Thyroid function tests, assessment for compressive symptoms, and evaluation for suspicious nodules requiring fine-needle aspiration biopsy should be documented.

The iodine-deficiency etiology must be distinguished from other causes of multinodular goiter.

MEAT Support

HCC Buddy guidance

Documentation should confirm multinodular thyroid enlargement attributed to iodine deficiency, with imaging (thyroid ultrasound) demonstrating multiple nodules.

Thyroid function tests, assessment for compressive symptoms, and evaluation for suspicious nodules requiring fine-needle aspiration biopsy should be documented.

The iodine-deficiency etiology must be distinguished from other causes of multinodular goiter.

Audit Caution

HCC Buddy guidance

Ensure documentation specifies multinodular morphology rather than diffuse enlargement to justify this code over E01.

In the absence of documented iodine deficiency, use E04.2 for multinodular goiter. If individual nodules require evaluation for malignancy, document fine-needle aspiration results and assign any associated thyroid neoplasm codes separately. Do not assign if the goiter is toxic (hyperthyroid); use the appropriate E05 code.

Common Mistakes

HCC Buddy guidance

E04.2 (Nontoxic multinodular goiter) is used when the multinodular goiter is not related to iodine deficiency.

E01.0 (Iodine-deficiency related diffuse goiter) is used for diffuse enlargement without nodules.

E05.20 (Thyrotoxicosis with toxic multinodular goiter) captures multinodular goiter with hyperthyroidism.

E01.2 (Iodine-deficiency related goiter, unspecified) is less specific.

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is E01.1 an HCC code?

E01.1 is not in the CMS-HCC V28 or V24 community payment model, but it does map to Thyroid and Parathyroid Disorders under the Part D RxHCC model.

Code: E01.1
Description: Iodine-deficiency related multinodular (endemic) goiter
HCC (V28): No CMS-HCC V28 mapping
RAF: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

RxHCCHCC 44, Thyroid and Parathyroid Disorders

0.070

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. 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.

Work E01.1 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for E01.1

For E01.1 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 E01.1 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

E01.1 is the ICD-10-CM diagnosis code for iodine-deficiency related multinodular (endemic) goiter. An enlarged thyroid gland with multiple nodules that develops in areas with low iodine in the diet, where the thyroid develops lumps rather than enlarging uniformly. E01.1 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).

E01.1 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 a CMS-HCC V28 payment category. Capture depends on documentation that supports the diagnosis; verify the HCC assignment against the current CMS mapping for the applicable payment year. Coders reviewing E01.1 should check whether additional documentation would support a more specific child code in the same hierarchy that does map to a payment HCC, capturing the correct specificity is the highest-impact RAF improvement available within accurate coding.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for E01.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Confirm the presence of multiple nodules through imaging or clinical documentation to differentiate from diffuse goiter
•Document any functional status of nodules (toxic vs. non-toxic) if available

Clinical Significance

Iodine-deficiency related multinodular (endemic) goiter represents the progression of chronic iodine deficiency to a thyroid gland with multiple autonomous nodules. This evolution from diffuse to nodular goiter typically occurs over years and carries a risk of toxic multinodular goiter with autonomous thyroid hormone production. Multinodular goiters can also cause compressive symptoms and harbor occult thyroid carcinoma requiring ongoing surveillance.

Documentation Requirements

✓Documentation should confirm multinodular thyroid enlargement attributed to iodine deficiency, with imaging (thyroid ultrasound) demonstrating multiple nodules.
✓Thyroid function tests, assessment for compressive symptoms, and evaluation for suspicious nodules requiring fine-needle aspiration biopsy should be documented.
✓The iodine-deficiency etiology must be distinguished from other causes of multinodular goiter.

Commonly Confused Codes

•E04.2 (Nontoxic multinodular goiter) is used when the multinodular goiter is not related to iodine deficiency.
•E01.0 (Iodine-deficiency related diffuse goiter) is used for diffuse enlargement without nodules.
•E05.20 (Thyrotoxicosis with toxic multinodular goiter) captures multinodular goiter with hyperthyroidism.
•E01.2 (Iodine-deficiency related goiter, unspecified) is less specific.