2026 ICD-10-CM Diagnosis Code T33.811SSuperficial frostbite of right ankle, sequela
T33.811S is a billable ICD-10-CM diagnosis code for superficial frostbite of right ankle, sequela. The 7th character S marks it as a sequela code, which reports a problem that remains after the original condition has resolved. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 922 through 923. The code is exempt from POA reporting. Coders also document this condition as frostbite of ankle. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Effect of other external causes, sequela.
Code Identity
Code Classification
Present on Admission (POA)Billing
T33.811S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Frostbite of ankle
- Frostbite of right ankle
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Superficial frostbite (T33). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Frostbite
Frostbite is an injury to the body that is caused by freezing. It most often affects the nose, ears, cheeks, chin, fingers, or toes. Frostbite can permanently damage the body, and severe cases can lead to amputation.
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Convert T33.811S to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T33.811SOverview
Is T33.811S (Superficial frostbite of right ankle) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report superficial frostbite of right ankle, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in T33.811S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the superficial frostbite of right ankle itself has resolved, not the original event.
What MS-DRG does T33.811S group to?
When superficial frostbite of right ankle, sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.
Is T33.811S exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for superficial frostbite of right ankle, sequela on inpatient claims.
What is the ICD-9 equivalent of T33.811S?
Under the General Equivalence Mappings, superficial frostbite of right ankle, sequela converts to ICD-9-CM 909.4 (late eff cert ext cause). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
