T31.21
BillableBurns involving 20-29% of body surface with 10-19% third degree burns
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is T31.21 an HCC code?
Yes. T31.21 maps to Severe Skin Burn or Condition under the CMS-HCC V28 risk adjustment model (and Severe Skin Burn or Condition under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for T31.21
For T31.21 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed T31.21 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
T31.21 is the ICD-10-CM diagnosis code for burns involving 20-29% of body surface with 10-19% third degree burns. A burn injury affecting 20-29% of the body surface area with 10-19% of the burn being deep (third degree). T31.21 sits in the ICD-10-CM chapter for injury, poisoning and certain other consequences of external causes (s00-t88), within the section covering burns and corrosions of multiple and unspecified body regions (t30-t32).
Under the CMS-HCC V28 risk adjustment model, T31.21 maps to Severe Skin Burn or Condition (HCC 385) with a community, non-dual, aged base RAF weight of 0.350. Under the older V24 model, T31.21 mapped to the same category but with a base RAF weight of 0.517 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
The second digit (1) indicates 10-19% third degree burns; this represents a moderate to severe burn requiring specialized care. Because T31.21 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for T31.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •The second digit (1) indicates 10-19% third degree burns; this represents a moderate to severe burn requiring specialized care
- •Document the extent of third degree burns carefully as this affects treatment decisions and prognosis
Clinical Significance
Burns involving 20-29% of body surface area with 10-19% third-degree involvement represent major burn injury requiring immediate hospitalization and specialized burn center care. This level of injury carries significant risk of complications including infection, fluid and electrolyte imbalances, and potential need for multiple surgical procedures.
Documentation Requirements
- ✓Precise calculation showing 20-29% total body surface area involvement
- ✓Documentation that 10-19% of the burn area is third-degree (full thickness)
- ✓Use of standardized burn assessment tools (Rule of Nines, Lund-Browder)
- ✓Description of burn depth characteristics consistent with third-degree injury
- ✓Documentation of anatomical distribution of burns
- ✓Assessment by burn-qualified healthcare provider
- ✓Evidence of systemic impact or complications from burn injury
- ✓Treatment protocols including fluid resuscitation and surgical planning
Commonly Confused Codes
- •T31.20 — Burns 20-29% TBSA with no third degree involvement
- •T31.22 — Burns 20-29% TBSA with 20-29% third degree (higher third-degree percentage)
- •T31.11 — Burns 10-19% TBSA with 10-19% third degree (smaller total area)
- •T32.21 — Corrosions 20-29% TBSA with 10-19% third degree (chemical injury)
- •T31.31 — Burns 30-39% TBSA with 10-19% third degree (larger total area)