ICD code T31.44 – Burns involving 40-49% of body surface with 40-49% third degree burns

Key takeaways

T31.44 is a billable ICD-10-CM code covering 40-49% TBSA burns where 40-49% of that area is third-degree injury, valid from October 1, 2025.

The fourth digit reports the third-degree share of the burned area in 10-point bands. T31.40 covers 0-9%, T31.41 covers 10-19%, and T31.44 covers 40-49%.

TBSA is calculated with the Rule of Nines for adults. The Lund-Browder chart is preferred for pediatric patients, whose body proportions differ by age.

T31 codes cover thermal burns classified by extent, and T32 codes cover corrosions. The mechanism of injury, not the depth, decides which category applies.

ICD-10 code T31.44: quick reference at a glance

The table below covers the core reference data coders and clinicians need before billing or documenting a T31.44 encounter. All details reflect the FY2026 ICD-10-CM edition.

What does ICD-10 code T31.44 mean clinically?

ICD-10 code T31.44 means the patient has thermal burns across 40-49% of total body surface area. Of that burned area, 40-49% is third-degree injury. Third-degree burns destroy the epidermis, dermis, and underlying subcutaneous tissue. They present as dry, leathery, or waxy wounds that are insensate at the burn site, because the sensory nerve endings have been destroyed.

The clinical picture at T31.44 is a major burn injury requiring intensive care. Patients typically need fluid resuscitation calculated from the Parkland formula, surgical debridement, and skin grafting over large surface areas. Wound-depth mapping has to be captured at each surgical encounter. The code at discharge can differ from the admission code once depth assessments are refined during treatment.

Two clinical distinctions matter for coding accuracy. First, third-degree burns are distinct from deep partial-thickness (deep second-degree) burns. Deep partial-thickness burns spare some dermal appendages and may be moist with reduced sensation, while third-degree burns spare none. Conflating the two changes the fourth digit.

Second, the 40-49% band has to be met twice over. The total burn extent and the third-degree subset must each fall inside it before T31.44 applies.

T31 burn coding TBSA: How the category structure works

The T31 category organizes burn diagnoses by the percentage of body surface area involved rather than by anatomical location. That is what separates T31 from the anatomically specific burn codes in T20-T25. When a burn spans several body regions, T31 gives a single code for overall severity based on extent.

The first digit after the decimal sets the TBSA range, in 10-point steps. T31.0 covers less than 10% TBSA, T31.4 covers 40-49%, and the series runs up to T31.9 for 90% or more. A recount that puts the total at 50-59% leaves the T31.4 group, and with 30-39% third degree the code is T31.53.

How the Rule of Nines determines your TBSA percentage

The Rule of Nines assigns a fixed percentage of body surface area to each anatomical region for adult patients. Clinicians sum the involved regions to obtain TBSA. The standard adult assignments are:

• Head and neck: 9%
• Each upper extremity: 9% (18% total)
• Anterior trunk: 18%
• Posterior trunk: 18%
• Each lower extremity: 18% (36% total)
• Perineum / genitalia: 1%

One route to 45% TBSA is the full posterior trunk at 18%, both upper extremities at 18%, and half of one lower extremity at 9%. The Lund-Browder chart is preferred for patients under 15, because head-to-leg proportions shift a great deal during development. In young children the Rule of Nines overstates head involvement and understates the legs. Any TBSA figure in the record should name the tool used, per CMS ICD-10-CM coding guidelines.

Understanding the fourth digit: Third-degree burn percentage in T31.4x

The fourth digit in the T31.4x subcategory specifies what proportion of the established TBSA burn is third-degree injury. The percentage is nested. It applies to the burned area only, not to the patient’s total body surface.

Take a 45% TBSA burn where 20 of those 45 points are third-degree. That is roughly 44% of the burned area, so T31.44 applies. If only 10 of the 45 points are third-degree, the share drops to 22% and T31.42 applies instead.

The five subcodes tile the range in continuous 10-point bands, so every third-degree proportion up to 49% has exactly one code. A calculated share of 35% lands in T31.43, and 41% moves the same claim to T31.44. The ladder below shows where each band sits.

T31 vs T32: Burns versus corrosions

T31 and T32 are parallel code categories. T31 covers thermal burns classified by extent, and T32 covers corrosions, meaning chemical burns, classified the same way. The mechanism of injury decides the category, not the wound depth or the TBSA.

A frequent coding error is applying T31.44 to a chemical plant injury where a corrosive agent caused the wound. The clinical appearance can be identical to a flame burn, but the ICD-10-CM Official Guidelines make the mechanism decide the category. Check the emergency department note or the incident report for language like “acid exposure,” “alkali splash,” or “chemical burn.” Any of those routes the claim to T32.44 instead.

Burn coding documentation requirements for T31.44

Supporting T31.44 through a claim takes documentation that goes well beyond the code description. Most burn coding denials come from missing TBSA measurement detail or thin burn-depth characterization, not from picking the wrong code. The clinical record has to answer five questions before the claim leaves the facility.

• Total TBSA percentage: The physician or advanced practice provider documents the burned surface area as a percentage. The note names the assessment tool used and confirms the figure falls in the 40-49% range.
• Third-degree burn percentage: The depth-specific breakdown is documented separately from total TBSA. A note reading “45% TBSA burn” does not support T31.44 without a line such as “of which approximately 42% is full-thickness.”
• Wound mapping or body surface diagram: Many burn centers complete a front-and-back body diagram at admission and update it at each surgical encounter. The diagram is the audit trail tying the percentages to anatomical locations.
• Burn depth characterization: The note distinguishes third-degree from deep partial-thickness in accepted terms. “Full-thickness,” “insensate,” “dry or leathery wound,” and “eschar formation” all defend the code. “Severe burn” alone does not.
• Mechanism of injury: A thermal cause such as flame, scald, contact, radiation, or electrical exposure has to be documented to support T31 over T32.

Depth estimates are often revised between admission and discharge, which is clinically normal as edema resolves and the wound demarcates. The discharge summary should explain any change from the admission code. The code that goes out on the claim has to match the discharge summary, not the emergency department triage note.

A downward revision can change both percentages at once. A patient remeasured at 35% total with 10-19% third degree no longer sits in T31.4, and the claim becomes ICD-10-CM code T31.31.

MS-DRG and reimbursement implications of T31.44

T31.44 maps to MS-DRG groups in the burn injury family under Medicare’s Inpatient Prospective Payment System (IPPS). Burns are among the highest-cost DRG categories, because of the ICU stays, repeat surgeries, and long rehabilitation they usually involve. Three things decide which MS-DRG a T31.44 encounter lands in. They are the procedure codes billed alongside the diagnosis, the discharge disposition, and any Major Complication or Comorbidity (MCC).

Under IPPS grouping logic, extensive burns with a large third-degree component commonly fall in MS-DRG 927. That group covers extensive or full-thickness burns with 96 or more ventilator hours plus a skin graft. Related burn DRG pairs pick up the rest, depending on ventilator hours and grafting performed. Weights and payment amounts are updated annually in the CMS IPPS Final Rule, so verify the current year before relying on any published figure.

Billing teams should expect payer requests for clinical records whenever the MS-DRG weight is this high. Three checks before submission:

• TBSA documentation supports the 40-49% level the code states, for both percentages.
• Procedure codes for grafting agree with the operative reports.
• Secondary diagnoses such as sepsis, inhalation injury, or fluid overload are coded and sequenced correctly.

Those secondary diagnoses shift DRG assignment, and some of them qualify as MCCs on their own. On the procedure side, surgical preparation of the burn wound before grafting is reported with CPT code 15002. The operative note behind it has to agree with the burn diagnosis on the same claim.

ICD-10-CM 2026 update: Is T31.44 still valid?

T31.44 is a valid, active ICD-10-CM code for FY2026. It became effective October 1, 2025, under the annual update cycle maintained by CMS and the National Center for Health Statistics (NCHS). The FY2026 update made no revisions to the T31.44 descriptor or its position in the T31 hierarchy.

The ICD-10-CM code set is updated every October 1. Checking the current edition against the CDC/NCHS ICD-10-CM web tool before billing confirms billable status and surfaces new inclusion or exclusion notes. T31.44 has kept the same description across recent editions. Coding guidelines, payer policies, and MS-DRG assignments can still change around a code that does not.

Coders working across the wider ICD-10-CM code set will recognize conventions that apply system-wide, such as seventh-character extensions for injury sequencing. T31.44 does not take a seventh character. The site-specific burn codes in T20-T25 do, using A for an initial encounter, D for a subsequent encounter, and S for sequela.

Approximate synonyms and clinical terminology for T31.44

Several clinical and administrative terms map to T31.44. Coders meet them in physician notes, operative reports, and trauma documentation, and should read them as equivalent expressions of the same diagnosis.

• Burns involving 40-49% body surface area with 40-49% full-thickness burns
• Major burn with 40-49% TBSA and 40-49% third-degree injury
• Extensive thermal burn, 40-49% total body surface area, 40-49% third-degree
• 40 to 49 percent total body surface area burn with 40 to 49 percent full-thickness involvement
• Burn classified by extent – 40-49% TBSA, 40-49% third degree
• ICD-10-CM T31.44 (abbreviated form used in burn registries and trauma databases)

Where the record says “full-thickness” rather than “third-degree,” the terms are interchangeable for coding purposes and ICD-10-CM accepts both. “Deep partial-thickness” and “deep second-degree” are not synonyms for third-degree. Neither supports T31.44 unless a physician recharacterizes the wound as full-thickness on a later assessment.

How Pabau keeps burn diagnosis codes consistent from admission to claim

A burn admission produces one diagnosis code on day one and a revised one after the first debridement. In most facilities those revisions sit in the operative notes, and the billing team finds out about them by reading the chart at discharge.

Practice management software like Pabau keeps the code, the wound-mapping note, and the claim on one patient record. Pabau’s software for billing teams flags encounters where the diagnosis changed mid-stay. The version that reaches the payer is then the one the discharge summary supports.

Coders can then open the documentation behind a T31.44 claim without logging into a second system. Denials that turn on TBSA detail get caught before submission rather than after the remittance arrives.

Keep burn coding consistent from admission to claim

Pabau links every diagnosis code to the clinical encounter behind it and flags mid-stay code changes. Billing teams get the documentation a payer will ask for, without a second system.

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Conclusion

The hard part of T31.44 is not finding the code. It is producing a record that shows two separate percentages, measured with a named tool, and revised in writing when the wound demarcates.

Practices that treat the wound-mapping diagram as a billing document spend less time answering payer record requests on high-weight burn claims. The diagram is what connects a percentage to an anatomical location, and it is the first thing a reviewer asks for.

Fix the documentation and the code follows. Book a demo to see how Pabau keeps burn diagnosis codes and their supporting notes on one record from admission through payment.

Continue your research

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