2026 ICD-10-CM Diagnosis Code A18.81Tuberculosis of thyroid gland

ICD-10-CM Codes›A00–B99›A15-A19›A18

ICD-10-CM A18.81
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A18.81 is a billable ICD-10-CM diagnosis code for tuberculosis of thyroid gland. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 643 through 645, 974 through 976. Coders also document this condition as thyroid infection. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Thyroid disorders and Tuberculosis.

Code Identity

ICD-10-CM Code
A18.81
Billable Status
Yes — Valid for Submission
Code Describes
Tuberculosis of thyroid gland
Short Description
Tuberculosis of thyroid gland
Same as the full description in the CMS dataset.
Parent Code
A18.8
Tuberculosis of other specified organs

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA15-A19Tuberculosis
CategoryA18Tuberculosis of other organs
This CodeA18.81Tuberculosis of thyroid gland

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Thyroid infection
  • Tuberculosis of thyroid gland

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Thyroiditis
      • tuberculous
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • thyroid gland

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR END001
Thyroid disorders
Default principal diagnosis: inpatient No · outpatient No
CCSR INF001
Tuberculosis
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Thyroid Diseases

Your thyroid is a small, butterfly-shaped gland in the front of your neck. It makes hormones that control the way the body uses energy. These hormones affect nearly every organ in your body and control many of your body's most important functions. For example, they affect your breathing, heart rate, weight, digestion, and moods.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert A18.81 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
017.50 TB of thyroid-unspec
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A18.81Overview

Is A18.81 (Tuberculosis of other specified organs) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report tuberculosis of thyroid gland on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does A18.81 group to?

When tuberculosis of thyroid gland is the principal diagnosis on an inpatient stay, it groups to MS-DRG 643, 644, 645, 974, 975, 976, with relative weights from 0.7683 to 2.8860 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A18.81?

Under the General Equivalence Mappings, tuberculosis of thyroid gland converts to ICD-9-CM 017.50 (TB of thyroid-unspec). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.