2027 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 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

A18.81 is a billable ICD-10-CM diagnosis code for tuberculosis of thyroid gland. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 643 through 645, 974 through 976. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 15 closely related codes. Coders also document this condition as infection of endocrine gland caused by Mycobacterium tuberculosis complex. 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.

  • Infection of endocrine gland caused by Mycobacterium tuberculosis complex
  • Infectious thyroiditis
  • Thyroid infection
  • Tuberculosis of thyroid gland

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A18.81: its own notes plus those printed at block A15-A19 and Chapter 1. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Block A15-A19 Tuberculosis applies to 51 codes
  • infections due to Mycobacterium tuberculosis and Mycobacterium bovis
From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • diseases generally recognized as communicable or transmissible

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From Block A15-A19 Tuberculosis applies to 51 codes
  • congenital tuberculosis (P37.0)
  • nonspecific reaction to test for tuberculosis without active tuberculosis (R76.1-)
  • pneumoconiosis associated with tuberculosis, any type in A15 (J65)
  • positive PPD (R76.11)
  • positive tuberculin skin test without active tuberculosis (R76.11)
  • sequelae of tuberculosis (B90.-)
  • silicotuberculosis (J65)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • carrier or suspected carrier of infectious disease (Z22.-)
  • certain localized infections - see body system-related chapters
  • infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
  • infectious and parasitic diseases specific to the perinatal period (P35-P39)
  • influenza and other acute respiratory infections (J00-J22)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Block A15-A19 Tuberculosis applies to 51 codes
  • code, if applicable, for associated cachexia (E88.A)
From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • code to identify resistance to antimicrobial drugs (Z16.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name A18.81, its category, or a range that includes it.

Applicable To 1

These notes mention A18.81.

  • O98.0 Tuberculosis complicating pregnancy, childbirth and the puerperium
    Conditions in A15-A19 names A15-A19, which includes this code

Excludes1 1

These codes carry an Excludes1 note naming A18.81: they are not reported together with it, unless the two conditions are unrelated.

  • E35 Disorders of endocrine glands in diseases classified elsewhere
    tuberculosis of thyroid gland (A18.81)

Excludes2 1

These codes carry an Excludes2 note naming A18.81: its condition is not part of those codes, and both may be reported when the patient has both.

  • A31 Infection due to other mycobacteria
    tuberculosis (A15-A19) names A15-A19, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About A18.81Overview

What is the ICD-10 code for tuberculosis of thyroid gland?

The ICD-10-CM code for tuberculosis of thyroid gland is A18.81 (sometimes written as A1881). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

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 974, 976, 644, 645, 975, 643, with relative weights from 0.7461 to 3.0488 depending on complications. Higher weights mean higher Medicare reimbursement.

Is A18.81 a CC or MCC?

CMS lists A18.81 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 15 closely related codes in its exclusion list.

Can A18.81 be reported with P37.0?

Not as a rule. The Excludes1 note at block A15-A19, which applies to A18.81, lists "congenital tuberculosis (P37.0)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).