T32.21
BillableCorrosions involving 20-29% of body surface with 10-19% third degree corrosion
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is T32.21 an HCC code?
Yes. T32.21 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 T32.21
For T32.21 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 T32.21 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
T32.21 is the ICD-10-CM diagnosis code for corrosions involving 20-29% of body surface with 10-19% third degree corrosion. Chemical burn affecting 20-29% of the body surface with moderate deep tissue damage (10-19% third degree burns). T32.21 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, T32.21 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, T32.21 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.
Burns of this extent typically require hospitalization and specialized burn care. Because T32.21 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 T32.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Burns of this extent typically require hospitalization and specialized burn care
- •Coordinate coding with documentation of fluid resuscitation needs and burn center consultation
Clinical Significance
Corrosions involving 20-29% of body surface area with 10-19% third-degree involvement represent major chemical burn injury requiring immediate specialized intervention and ongoing monitoring for systemic toxicity. Chemical burns can continue progressing for hours after initial exposure, making aggressive decontamination, neutralization protocols, and continuous assessment critical for optimal outcomes.
Documentation Requirements
- ✓Documentation of 20-29% total body surface area chemical involvement
- ✓Clear documentation that 10-19% of affected area has third-degree corrosion
- ✓Identification and documentation of the causative chemical agent
- ✓Detailed documentation of decontamination and neutralization procedures
- ✓Assessment of chemical burn progression and ongoing tissue damage
- ✓Evidence of specialized chemical burn treatment protocols
- ✓Monitoring for systemic toxicity and chemical-specific complications
- ✓Documentation of multidisciplinary care including toxicology consultation
Commonly Confused Codes
- •T31.21 — Thermal burns 20-29% TBSA with 10-19% third degree (thermal, not chemical)
- •T32.20 — Corrosions 20-29% TBSA with no third degree involvement
- •T32.22 — Corrosions 20-29% TBSA with 20-29% third degree (more third-degree)
- •T32.11 — Corrosions 10-19% TBSA with 10-19% third degree (smaller total area)
- •T32.31 — Corrosions 30-39% TBSA with 10-19% third degree (larger total area)