What is ICD-10 code T32.21?

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 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. T32.21 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. T32.21 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. T32.21 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for T32.21?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For T32.21, V28 maps to Severe Skin Burn or Condition at RAF 1.291 while V24 mapped to Severe Skin Burn or Condition at RAF 0.224. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting T32.21?

Burns of this extent typically require hospitalization and specialized burn care Coordinate coding with documentation of fluid resuscitation needs and burn center consultation Because T32.21 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

2026 ICD-10-CM T32.21: Corrosions involving 20-29%

ICD-10-CM Code View

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Code lookupT32.21Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Injury, poisoning and certain other consequences of external causes (S00-T88) / Burns and corrosions of multiple and unspecified body regions (T30-T32)

T32.21

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

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).

Buddy Insight

CMS-HCC V28

Mapped

HCC 385

Severe Skin Burn or Condition

RAF 1.291

CMS-HCC V24

Mapped

HCC 162

Severe Skin Burn or Condition

RAF 0.224

ACA/HHS

Mapped

HCC 218

HHS-HCC 218

Varies by metal level

ESRD/PACE

Mapped

HCC 162

Severe Skin Burn or Condition

RAF 0.155

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

T32Corrosions classified according to extent of body surface involved

T32.2Corrosions involving 20-29% of body surface

T32.21Corrosions involving 20-29% of body surface with 10-19% third degree corrosion

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for T32.21 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for T32.21 in this effective period.

Related Child Codes

Official

T32.20Corrosions involving 20-29% of body surface with 0% to 9% third degree corrosion

T32.22Corrosions involving 20-29% of body surface with 20-29% third degree corrosion

Includes

Official

ICD-10-CM does not list Includes notes for T32.21 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for T32.21 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for T32.21 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for T32.21 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for T32.21 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

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

MEAT Support

HCC Buddy guidance

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

Audit Caution

HCC Buddy guidance

Failing to distinguish chemical corrosions from thermal burns

Not recognizing the progressive nature of chemical tissue damage

Inadequate documentation of chemical-specific treatment protocols

Missing the need for ongoing assessment of chemical burn progression

Common Mistakes

HCC Buddy guidance

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)

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is T32.21 an HCC code?

Yes. T32.21 (Corrosions involving 20-29% of body surface with 10-19% third degree corrosion) maps to Severe Skin Burn or Condition under the CMS-HCC V28 risk adjustment model (and Severe Skin Burn or Condition under V24), with a community non-dual aged RAF of 1.291. It is billable for payment year 2026.

Coder answer: T32.21 is billable and maps to V28 HCC 385, Severe Skin Burn or Condition. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: T32.21
Description: Corrosions involving 20-29% of body surface with 10-19% third degree corrosion
HCC (V28): HCC 385 — Severe Skin Burn or Condition
RAF: 1.291
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 385, Severe Skin Burn or Condition

1.291

V24HCC 162, Severe Skin Burn or Condition

0.224

ESRDHCC 162, Severe Skin Burn or Condition

0.155

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. 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.

Work T32.21 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

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.

Coder workflow notes

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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 1.291. Under the older V24 model, T32.21 mapped to the same category but with a base RAF weight of 0.224, 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)