2027 ICD-10-CM Diagnosis Code T34.42XAFrostbite with tissue necrosis of left arm, initial encounter

ICD-10-CM Codes›S00–T88›T33-T34›T34

ICD-10-CM T34.42XA
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

T34.42XA is a billable ICD-10-CM diagnosis code for frostbite with tissue necrosis of left arm, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 922 through 923. 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 77 closely related codes. Coders also document this condition as tissue necrosis of left upper limb due to and following frostbite. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Effect of other external causes, initial encounter.

Code Identity

ICD-10-CM Code
T34.42XA
Billable Status
Yes — Valid for Submission
Code Describes
Frostbite with tissue necrosis of left arm, initial encounter
Short Description
Frostbite with tissue necrosis of left arm, init encntr
Parent Code
T34.42
Frostbite with tissue necrosis of left arm

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT33-T34Frostbite
CategoryT34Frostbite with tissue necrosis
This CodeT34.42XAFrostbite with tissue necrosis of left arm, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Tissue necrosis of left upper limb due to and following frostbite

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Frostbite with tissue necrosis (T34). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to T34.42XA: its own notes plus those printed at T34.4, T34, block T33-T34, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.

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 T34.4 Frostbite with tissue necrosis of arm applies to 9 codes
  • frostbite with tissue necrosis of wrist and hand (T34.5-)
From Block T33-T34 Frostbite applies to 222 codes
  • hypothermia and other effects of reduced temperature (T68, T69.-)
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes

Use Additional Code

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

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • code to identify any retained foreign body, if applicable (Z18.-)

Notes

General instructions on how these codes are used.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
  • The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.

7th Character

Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.

From T34 Frostbite with tissue necrosis applies to 111 codes
  • The appropriate 7th character is to be added to each code from category T34
Values for category T34 Encounter: Initial, Subsequent, Sequela
  • Ainitial encounter this code
  • Dsubsequent encounter
  • Ssequela

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

Clinical ClassificationClinical

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

CCSR INJ021
Effect of other external causes, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Frostbite

Frostbite is an injury to the body that is caused by freezing. It most often affects the nose, ears, cheeks, chin, fingers, or toes. Frostbite can permanently damage the body, and severe cases can lead to amputation.

Read the full article at MedlinePlus

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

Convert T34.42XA to ICD-9-CMHistory

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

ICD-9-CM
991.3 Frostbite NEC/NOS
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 T34.42XAOverview

What is the ICD-10 code for frostbite with tissue necrosis of left arm, initial encounter?

The ICD-10-CM code for frostbite with tissue necrosis of left arm, initial encounter is T34.42XA (sometimes written as T3442XA). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is T34.42XA (Frostbite with tissue necrosis of left arm) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report frostbite with tissue necrosis of left arm, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character A in T34.42XA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for frostbite with tissue necrosis of left arm, such as an emergency visit or first evaluation.

What MS-DRG does T34.42XA group to?

When frostbite with tissue necrosis of left arm, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 923, 922, with relative weights from 0.9980 to 1.6248 depending on complications. Higher weights mean higher Medicare reimbursement.

Is T34.42XA a CC or MCC?

CMS lists T34.42XA 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 77 closely related codes in its exclusion list.