2026 ICD-10-CM Diagnosis Code T54.2X4AToxic effect of corrosive acids and acid-like substances, undetermined, initial encounter
T54.2X4A is a billable ICD-10-CM diagnosis code for toxic effect of corrosive acids and acid-like substances, undetermined, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 917 through 918. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: fire/burn; initial encounter; External cause codes: intent of injury, undetermined; and Toxic effects, initial encounter.
Code Identity
Code Classification
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Toxic effect of corrosive substances (T54). 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.
Clinical InformationClinical
Oxalates
derivatives of oxalic acid. included under this heading are a broad variety of acid forms, salts, esters, and amides that are derived from the ethanedioic acid structure.Oxalic Acid
a strong dicarboxylic acid occurring in many plants and vegetables. it is produced in the body by metabolism of glyoxylic acid or ascorbic acid. it is not metabolized but excreted in the urine. it is used as an analytical reagent and general reducing agent.
Table of Drugs and ChemicalsClinical
Substances in the Table of Drugs and Chemicals that reference this code family. Always confirm in the Tabular List before coding.
| Substance | Accidental | Self-harm | Assault | Undetermined | Adverse Effect | Underdosing |
|---|---|---|---|---|---|---|
| Acetic | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Acetic::acid | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Acetic::acid::with sodium acetate (ointment) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Acetic::acid::ester (solvent) (vapor) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Acetic::acid::irrigating solution | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Acetic::acid::medicinal (lotion) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Acetic::anhydride | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Acetic::ether (vapor) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Acid (corrosive) NEC | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Aqua fortis | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Battery acid or fluid | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Formic acid | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Formic acid::vapor | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Hydrazoic acid, azides | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Hydrochloric acid (liquid) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Hydrochloric acid (liquid)::medicinal (digestant) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Hydrochloric acid (liquid)::vapor | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Hydrofluoric acid (liquid) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Hydrofluoric acid (liquid)::vapor | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Mineral | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Mineral::acids | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Mineral::oil (laxative) (medicinal) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Mineral::oil (laxative) (medicinal)::emulsion | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Mineral::oil (laxative) (medicinal)::nonmedicinal | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Mineral::oil (laxative) (medicinal)::topical | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Mineral::salt NEC | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Mineral::spirits | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Nitric | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Nitric::acid (liquid) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Nitric::acid (liquid)::vapor | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Nitric::oxide (gas) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Nitrohydrochloric acid | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Nitrous | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Nitrous::acid (liquid) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Nitrous::acid (liquid)::fumes | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Nitrous::ether spirit | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Nitrous::oxide | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Orthotolidine (reagent) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Osmic acid (liquid) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Osmic acid (liquid)::fumes | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Oxalic acid | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Oxalic acid::ammonium salt | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Phosphoric acid | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Picric (acid) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Saniflush (cleaner) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Storage battery (cells) (acid) | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Sulfuric acid | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Trichloroacetic acid, Trichloracetic acid | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
| Trichloroacetic acid, Trichloracetic acid::medicinal | T54.2X1 | T54.2X2 | T54.2X3 | T54.2X4 | – | – |
Convert T54.2X4A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T54.2X4AOverview
Is T54.2X4A a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of corrosive acids and acid-like substances, undetermined, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T54.2X4A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for toxic effect of corrosive acids and acid-like substances, undetermined, such as an emergency visit or first evaluation.
What MS-DRG does T54.2X4A group to?
When toxic effect of corrosive acids and acid-like substances, undetermined, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of T54.2X4A?
Under the General Equivalence Mappings, toxic effect of corrosive acids and acid-like substances, undetermined, initial encounter converts to ICD-9-CM 983.1 (toxic effect acids) and E924.1 (accid-caustic substance). 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.
