T33.4 ICD-10-CM Code: Superficial frostbite of arm

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for T33.4 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on T33.4 itself; “inherited from” names the category or block whose note applies here.

7th Character Guide

"The appropriate 7th character is to be added to each code from category T33"

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

How the encounter character is assigned. “Initial encounter” means the patient is receiving active treatment for the condition — it is not limited to the first visit, and a different or new provider giving active treatment still assigns it. “Subsequent encounter” covers care during the healing or recovery phase after active treatment. “Sequela” is for complications or conditions that arise as a direct result of the original condition.

ICD-10-CM Official Guidelines for Coding and Reporting, Section I.C.19.a (paraphrased by MedCoder).

Variant codes in this family

T33.40XA, T33.40XD, T33.40XS, T33.41XA, T33.41XD, T33.41XS, T33.42XA, T33.42XD

Character meanings are CMS's official 7th-character extensions for this family, as carried in each variant code's official description; variant codes are registry rows. The explanation of how the encounter character is assigned is MedCoder editorial, distinct from the official content above it.

Coder workflow for T33.4

MedCoder structured workflow — derived from this code’s own official record

Before you code T33.4

1. T33.4 is not reportable as written. Select the more specific code beneath it that the documentation supports. Codes are reported to the highest level of specificity the classification provides (Guidelines I.B.2).

   ReviewT33.40, T33.41, T33.42

   See the relationships section · Guide: How to choose an ICD-10-CM code →

2. A 7th character is required in this family. Confirm the documented encounter: initial (active treatment), subsequent (healing or recovery phase), or sequela. T33.4 is not valid without one. “Initial” means active treatment, not the first visit (Guidelines I.C.19.a).

   See the 7th Character Guide · Guide: 7th characters: initial, subsequent, sequela →

3. Confirm the injury type, the anatomical site at the most specific level documented, laterality where the family codes it, and the encounter for the 7th character. Each injury is coded separately unless the classification provides a combination code, and a superficial injury is not coded when a more severe injury of the same site is documented. Injury chapter guidelines (Guidelines I.C.19.b, I.C.19.b.1).

   Guide: 7th characters: initial, subsequent, sequela →

Choose the right path

1. Does the documentation support one of the more specific codes beneath T33.4?
   Yes → Select that code and continue the checks below on its own page.
   No → T33.4 cannot be reported as written; query for the specificity its subcategory needs.

   ReviewT33.40, T33.41, T33.42

2. Is the encounter phase documented — active treatment, healing or recovery, or a sequela?
   Yes → Assign the matching 7th character; the variant codes are in the 7th Character Guide.
   No → The code is invalid without its 7th character — query for the missing element.

Consider T33.4. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement

Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Anatomical site

At the most specific level the record states; a site the classification separates cannot be assumed from a procedure or a measurement.

Encounter type

Active treatment, healing or recovery phase, or sequela — the basis of the 7th character (Guidelines I.C.19.a).

External cause, place and activity

For the external cause codes reported with the injury or poisoning, where documented (Guidelines I.C.20.a).

Official instructions as workflow

• Excludes2 — not part of T33.4(2 notes)

  Coding workflow: The conditions named in this note are not included in T33.4. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

  CompareT33.5, T68, T69

  See the official tabular notes · Guidelines I.A.12.b

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Don’t confuse T33.4 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of T33.4 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• T33.40XA— Encounter relationship (Review)

  Same underlying diagnosis, different encounter phase.

  The same diagnosis at a different phase of care; one encounter takes one 7th character.

  What moves you there: Documentation of a initial encounter moves the case to T33.40XA.

  Full comparison: T33.4 vs T33.40XA →

• T33.40XD— Encounter relationship (Review)

  Same underlying diagnosis, different encounter phase.

  The same diagnosis at a different phase of care; one encounter takes one 7th character.

  What moves you there: Documentation of a subsequent encounter moves the case to T33.40XD.

  Full comparison: T33.4 vs T33.40XD →

• T33.5— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of superficial frostbite of wrist and hand adds T33.5; it is not part of this code and both may be reported when both are documented.

  Full comparison: T33.4 vs T33.5 →

• T68— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of hypothermia and other effects of reduced temperature adds T68; it is not part of this code and both may be reported when both are documented.

  Full comparison: T33.4 vs T68 →

• T69— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of hypothermia and other effects of reduced temperature adds T69; it is not part of this code and both may be reported when both are documented.

  Full comparison: T33.4 vs T69 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Verify Before Coding

• Not billable as written — a more specific code is required: T33.40XA, T33.40XD, T33.40XS, T33.41XA, T33.41XD.
• Requires a 7th character. "The appropriate 7th character is to be added to each code from category T33" Options: T33.40XA, T33.40XD, T33.40XS, T33.41XA, T33.41XD, T33.41XS

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name T33.4 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes1 note: T07 — Unspecified multiple injuries (via T33.-).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 112 Excludes2 notes across 2 chapters: I73 — Other peripheral vascular diseases (via T33.-), S00 — Superficial injury of head (via T33.-), S00-S09 — Injuries to the head (S00-S09) (via T33.-), S01 — Open wound of head (via T33.-), S02 — Fracture of skull and facial bones (via T33.-), S03 — Dislocation and sprain of joints and ligaments of head (via T33.-), S04 — Injury of cranial nerve (via T33.-), S05 — Injury of eye and orbit (via T33.-), S06 — Intracranial injury (via T33.-), S07 — Crushing injury of head (via T33.-), S08 — Avulsion and traumatic amputation of part of head (via T33.-), S09 — Other and unspecified injuries of head (via T33.-), S10 — Superficial injury of neck (via T33.-), S10-S19 — Injuries to the neck (S10-S19) (via T33.-), S11 — Open wound of neck (via T33.-), S12 — Fracture of cervical vertebra and other parts of neck (via T33.-), S13 — Dislocation and sprain of joints and ligaments at neck level (via T33.-), S14 — Injury of nerves and spinal cord at neck level (via T33.-), S15 — Injury of blood vessels at neck level (via T33.-), S16 — Injury of muscle, fascia and tendon at neck level (via T33.-), +92 more.

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Related Codes

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Frostbite”; these codes share that main term but sit in a different category of the Tabular List.

T34.01 — Frostbite with tissue necrosis of ear (ear, with tissue necrosis), T34.02 — Frostbite with tissue necrosis of nose (nose, with tissue necrosis), T34.09 — Frostbite with tissue necrosis of other part of head (head, with tissue necrosis), T34.1 — Frostbite with tissue necrosis of neck (neck, with tissue necrosis), T34.2 — Frostbite with tissue necrosis of thorax (thorax, with tissue necrosis), T34.3 — Frostbite with tissue necrosis of abdominal wall, lower back and pelvis (pelvis, with tissue necrosis), T34.4 — Frostbite with tissue necrosis of arm (arm, with tissue necrosis), T34.51 — Frostbite with tissue necrosis of wrist (wrist, with tissue necrosis), T34.52 — Frostbite with tissue necrosis of hand (hand, with tissue necrosis), T34.53 — Frostbite with tissue necrosis of finger(s) (finger, with tissue necrosis), T34.6 — Frostbite with tissue necrosis of hip and thigh (hip, with tissue necrosis), T34.7 — Frostbite with tissue necrosis of knee and lower leg (knee, with tissue necrosis), T34.81 — Frostbite with tissue necrosis of ankle (ankle, with tissue necrosis), T34.82 — Frostbite with tissue necrosis of foot (foot, with tissue necrosis), T34.83 — Frostbite with tissue necrosis of toe(s) (toes, with tissue necrosis), T34.90 — Frostbite with tissue necrosis of unspecified sites (with, tissue necrosis), T34.99 — Frostbite with tissue necrosis of other sites (leg, with tissue necrosis)

Contextual Map

Every relationship of T33.4 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run T33.4 with these 10 related codes in Claim Check

Hierarchy

• S00-T88 — Chapter 19: Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) (S00-T88)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• T33-T34 — Frostbite[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Excludes2

• T33.5 — Superficial frostbite of wrist, hand, and fingers[Excludes2]: “superficial frostbite of wrist and hand (T33.5-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Excludes1 notes

• T07 — Unspecified multiple injuries[Excludes1](via T33.-): “frostbite (T33-T34)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Excludes2 notes (112)

• I73 — Other peripheral vascular diseases[Excludes2](via T33.-): “frostbite (T33-T34)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S00 — Superficial injury of head[Excludes2](via T33.-): “frostbite (T33-T34)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S00-S09 — Injuries to the head (S00-S09)[Excludes2](via T33.-): “frostbite (T33-T34)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S01 — Open wound of head[Excludes2](via T33.-): “frostbite (T33-T34)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S02 — Fracture of skull and facial bones[Excludes2](via T33.-): “frostbite (T33-T34)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S03 — Dislocation and sprain of joints and ligaments of head[Excludes2](via T33.-): “frostbite (T33-T34)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S04 — Injury of cranial nerve[Excludes2](via T33.-): “frostbite (T33-T34)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S05 — Injury of eye and orbit[Excludes2](via T33.-): “frostbite (T33-T34)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• and 104 more

Nearest codes (40)

• T33 — Superficial frostbite[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• T33.02 — Superficial frostbite of nose[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• T33.02XA — Superficial frostbite of nose, initial encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• T33.02XD — Superficial frostbite of nose, subsequent encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• T33.02XS — Superficial frostbite of nose, sequela[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• T33.09 — Superficial frostbite of other part of head[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• T33.09XA — Superficial frostbite of other part of head, initial encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• T33.09XD — Superficial frostbite of other part of head, subsequent encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 32 more

Change history

• FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Common coding questions

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data

CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page

Claim edits Official source data

CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page

Change history and date-of-service validity Official source data

CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page

Comparisons, relationships and the contextual map MedCoder structured relationship

Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears

Summary and FAQ answers MedCoder explanation

Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Nearest Codes in This Family

Official ICD-10-CM classifications closest to T33.4 in its code family, with their registry titles.

• T33.2XXS — Superficial frostbite of thorax, sequela
• T33.3 — Superficial frostbite of abdominal wall, lower back and pelvis
• T33.3XXA — Superficial frostbite of abdominal wall, lower back and pelvis, initial encounter
• T33.3XXD — Superficial frostbite of abdominal wall, lower back and pelvis, subsequent encounter
• T33.3XXS — Superficial frostbite of abdominal wall, lower back and pelvis, sequela
• T33.40 — Superficial frostbite of unspecified arm
• T33.40XA — Superficial frostbite of unspecified arm, initial encounter
• T33.40XD — Superficial frostbite of unspecified arm, subsequent encounter
• T33.40XS — Superficial frostbite of unspecified arm, sequela
• T33.41 — Superficial frostbite of right arm

View all codes in the T33 family