How Do You Code a Third-Degree Burn in ICD-10-CM?
Code a third-degree burn by first identifying the body site and burn depth and assigning a code from categories T20–T25 (with laterality and the 7th character for encounter type). When burns involve multiple or unspecified regions, add a code from T31.- (burns) or T32.- (corrosions) to show the percentage of total body surface area (TBSA) involved, including the portion that is third-degree. Sequence the highest-degree burn first, unless the circumstances of the admission indicate a different principal diagnosis. When several degrees affect the same site, report only the highest degree for that site.
What Is a Third-Degree (Full-Thickness) Burn?
A third-degree burn, also called a full-thickness burn, is a severe injury that destroys the epidermis and dermis and may extend into the subcutaneous tissue. Clinical features include:
- Skin that looks dry, leathery, stiff, or waxy
- Coloration ranging from white and brown to black
- Reduced or absent sensation in the affected area, because the full thickness of skin is destroyed
What Documentation Do Coders Need for Third-Degree Burns?
Before choosing a code, the medical record should clearly identify the anatomical site and the depth of the burn. Complete documentation includes:
| Documentation element | Why it matters |
|---|---|
| Specific body site | Supports selection from categories T20–T25 |
| Burn depth (degree) | Determines the 5th/6th character of the code |
| Laterality (left, right, bilateral) | Needed for site-specific codes where applicable |
| Encounter type (initial, subsequent, sequela) | Determines the 7th character |
| Each site and its degree, when multiple sites are involved | Supports complete and accurate code assignment |
| Intent (accidental, intentional self-harm, assault, undetermined) | Supports external cause codes |
| Activity and place of occurrence | Provides context for injury reporting and analysis |
ICD-10-CM Categories T20–T25: Site-Specific Burn Codes
Categories T20–T25 cover burns and corrosions by anatomical region:
| Category range | Region |
|---|---|
| T20 | Head, face, and neck |
| T21 | Trunk |
| T22 | Shoulder and upper limb, except wrist and hand |
| T23 | Wrist and hand |
| T24 | Hip and lower limb, except ankle and foot |
| T25 | Ankle and foot |
Examples of third-degree burn codes:
- T20.3-: third-degree burn of the head, face, and neck
- T23.3-: third-degree burn of the wrist and hand
- T24.3-: third-degree burn of the hip and lower limb, excluding the ankle and foot
These codes show where the burn occurred and how deep the tissue injury is. Remember to add the laterality and 7th character required for the specific code.
Extent of Body Surface Involved: T31.- and T32.- Codes
Site-specific codes do not tell you how much of the body is affected. An additional code from T31.- (burns classified by extent of body surface involved) or T32.- (corrosions classified by extent of body surface involved) identifies the percentage of total body surface area (TBSA) involved, including the proportion attributable to third-degree burns when known. This is used when burns affect multiple or unspecified body regions.
Example: T31.41 describes burns involving 40–49% of the body surface, with 10–19% third-degree burns.
The clinician may estimate TBSA with an accepted method, such as the Rule of Nines in adults, as long as the estimate is clinically appropriate and adequately documented.
The Rule of Nines: Estimating TBSA in Adults
The Rule of Nines divides the adult body into regions, each assigned a percentage of TBSA:
| Body region | % TBSA |
|---|---|
| Head and neck | 9% |
| Each arm | 9% |
| Each leg | 18% |
| Chest and abdomen | 18% |
| Upper and lower back | 18% |
| Perineal region | 1% |
Add the percentages of all affected regions to estimate total TBSA burned. Example: burns to the entire right arm (9%) and the chest and abdomen (18%) equal an estimated 27% TBSA.
This estimate supports selection of the correct T31.- or T32.- code, including the percentage that is third-degree. For children, body proportions differ from adults, so adjustments or alternative assessment methods may be needed.
Burn Sequencing Guidelines in ICD-10-CM
Sequencing depends on the severity of the burns, the anatomical sites involved, and the circumstances of the encounter.
Rule 1: Highest-Degree Burn First
When a patient has multiple burns, sequence the code for the highest-degree burn first. This also applies when the reason for the encounter is treatment of multiple external burns.
Example: A third-degree burn of the right hand and a second-degree burn of the left forearm. Sequence the third-degree burn first, followed by the second-degree burn.
Rule 2: Internal Burns, Inhalation Injury, and Related Conditions
When a patient has both internal and external burns, or is admitted with burns plus related conditions such as smoke inhalation or respiratory failure, the circumstances of the admission determine the principal or first-listed diagnosis. Review the clinical documentation to establish the reason for the encounter instead of relying on burn severity alone.
Rule 3: Same Site, Different Degrees
When burns of different degrees affect the same anatomical site and the same side of the body, assign the code for the highest degree documented for that site rather than separate codes for each degree.
Example: Second- and third-degree burns of the right thigh are reported with the code for the third-degree burn of the right thigh, with the appropriate encounter character.
Rule 4: Avoid T30.- When Specific Sites Are Documented
Do not use T30.- (burn and corrosion, body region unspecified) when the record provides specific anatomical details.
Rule 5: Use T31.- and T32.- Correctly
Categories T31.- and T32.- should be reserved for cases where the individual sites are not specified in the record. Under the guidelines summarized here:
- When the burn site is unspecified, a T31.- or T32.- code may be used as the primary code.
- When the site is specified, the T31.- or T32.- code is generally used as a supplementary code.
These codes provide important information about overall injury severity and support clinical reporting, burn-center analysis, and mortality assessment.
Coding Example: Unspecified Sites With Extensive Burns
A patient is admitted with burns involving 60–69% of the body surface, with 30–39% third-degree burns, caused by a house fire. The documentation does not specify the burn sites.
- Burn code: T31.63 (burns involving 60–69% of body surface with 30–39% third-degree burns)
- Then: any applicable external cause codes (such as intent, activity, and place of occurrence)
Third-Degree Burn Coding Checklist
- Is the body site documented for every burn?
- Is the depth (degree) documented for each site?
- Are laterality and encounter type (initial, subsequent, sequela) clear?
- Is TBSA documented, including the percentage of third-degree burns, with the estimation method?
- Is the highest-degree burn sequenced first, unless admission circumstances dictate otherwise?
- Are same-site burns of different degrees reported with only the highest degree?
- Are T30.-, T31.-, and T32.- used only as appropriate for the documentation?
- Are intent, activity, and place of occurrence documented for external cause codes?
Frequently Asked Questions (FAQ)
What is a third-degree burn?
A third-degree (full-thickness) burn destroys the epidermis and dermis and may reach the subcutaneous tissue. It can look dry, leathery, stiff, or waxy, and the area may have reduced sensation.
Which ICD-10-CM categories cover third-degree burns by body site?
Categories T20–T25 cover burns and corrosions of the head and neck, trunk, shoulder and upper limb, wrist and hand, hip and lower limb, and ankle and foot.
What is the ICD-10-CM code for a third-degree burn of the wrist and hand?
T23.3- identifies a third-degree burn of the wrist and hand. Add the laterality and 7th character required.
What does T31.41 mean?
T31.41 describes burns involving 40–49% of the body surface, with 10–19% of the body surface affected by third-degree burns.
How is TBSA estimated for coding?
Clinicians may use an accepted method such as the Rule of Nines in adults, as long as the estimate is clinically appropriate and documented. Children may need adjusted methods.
Which burn is sequenced first when a patient has multiple burns?
Generally the highest-degree burn, unless the circumstances of the admission (for example, inhalation injury or respiratory failure) indicate a different principal diagnosis.
How do I code second- and third-degree burns on the same site?
Assign the code for the highest degree documented for that site (for example, third-degree burn of the right thigh), not separate codes for each degree.
When should T30.- be avoided?
Avoid T30.- when the documentation provides specific anatomical details of the burn.
Key Takeaways
- Start with site, depth, laterality, and encounter type to select from T20–T25.
- Add T31.-/T32.- to report TBSA and the third-degree percentage when multiple or unspecified regions are involved.
- Sequence the highest-degree burn first, but let admission circumstances decide the principal diagnosis for internal burns and related conditions.
- Report the highest degree only for burns at the same site and side.
- Avoid T30.- when specific sites are documented.
- Document intent, activity, and place to support external cause codes.
Disclaimer: This article is for educational purposes and does not replace the official ICD-10-CM Official Guidelines for Coding and Reporting. Always verify codes against the current code set and follow your organization’s policies.
