2027 ICD-10-CM Diagnosis Code T33.831ASuperficial frostbite of right toe(s), initial encounter

ICD-10-CM Codes›S00–T88›T33-T34›T33

ICD-10-CM T33.831A
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

T33.831A is a billable ICD-10-CM diagnosis code for superficial frostbite of right toe(s), 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 44 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Effect of other external causes, initial encounter.

Code Identity

ICD-10-CM Code
T33.831A
Billable Status
Yes — Valid for Submission
Code Describes
Superficial frostbite of right toe(s), initial encounter
Short Description
Superficial frostbite of right toe(s), initial encounter
Same as the full description in the CMS dataset.
Parent Code
T33.831
Superficial frostbite of right toe(s)

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT33-T34Frostbite
CategoryT33Superficial frostbite
This CodeT33.831ASuperficial frostbite of right toe(s), initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Frostbite of all toes of right foot
  • Frostbite of fifth toe
  • Frostbite of fourth toe
  • Frostbite of great toe
  • Frostbite of right fifth toe
  • Frostbite of right foot
  • Frostbite of right fourth toe
  • Frostbite of right great toe
  • Frostbite of right second toe
  • Frostbite of right third toe
  • Frostbite of second toe
  • Frostbite of third toe
  • Frostbite of toe of right foot

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Superficial frostbite (T33). 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 T33.831A: its own notes plus those printed at T33, block T33-T34, and Chapter 19. 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 T33 Superficial frostbite applies to 111 codes
  • frostbite with partial thickness skin loss

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 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 T33 Superficial frostbite applies to 111 codes
  • The appropriate 7th character is to be added to each code from category T33
Values for category T33 Encounter: Initial, Subsequent, Sequela
  • Ainitial encounter this code
  • Dsubsequent encounter
  • Ssequela

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

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name T33.831A, its category, or a range that includes it.

Excludes2 1

These codes carry an Excludes2 note naming T33.831A: its condition is not part of those codes, and both may be reported when the patient has both.

  • T33.7 Superficial frostbite of knee and lower leg
    superficial frostbite of ankle and foot (T33.8-) names T33.8-, which includes this code

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 T33.831A to ICD-9-CMHistory

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

ICD-9-CM
991.2 Frostbite of foot
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 T33.831AOverview

What is the ICD-10 code for superficial frostbite of right toe(s), initial encounter?

The ICD-10-CM code for superficial frostbite of right toe(s), initial encounter is T33.831A (sometimes written as T33831A). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is T33.831A (Superficial frostbite of right toe(s)) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report superficial frostbite of right toe(s), initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character A in T33.831A mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for superficial frostbite of right toe(s), such as an emergency visit or first evaluation.

What MS-DRG does T33.831A group to?

When superficial frostbite of right toe(s), 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 T33.831A a CC or MCC?

CMS lists T33.831A 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 44 closely related codes in its exclusion list.