2027 ICD-10-CM Diagnosis Code T52.821AToxic effect of cycloparaffins, accidental (unintentional), initial encounter
T52.821A is a billable ICD-10-CM diagnosis code for toxic effect of cycloparaffins, accidental (unintentional), 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 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 917 through 918.
Code Identity
Code Classification
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Toxic effect of organic solvents (T52). 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 2027, published by CMS and the National Center for Health Statistics.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to T52.821A: its own notes plus those printed at T52, block T51-T65, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- halogen derivatives of aliphatic and aromatic hydrocarbons (T53.-)
- contact with and (suspected) exposure to toxic substances (Z77.-)
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify any retained foreign body, if applicable (Z18.-)
Notes
General instructions on how these codes are used.
- When no intent is indicated code to accidental. Undetermined intent is only for use when there is specific documentation in the record that the intent of the toxic effect cannot be determined.
- Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
- The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.
7th Character
Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.
- The appropriate 7th character is to be added to each code from category T52
- Ainitial encounter this code
- Dsubsequent encounter
- Ssequela
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Clinical InformationClinical
Cycloparaffins
alicyclic hydrocarbons in which three or more of the carbon atoms in each molecule are united in a ring structure and each of the ring carbon atoms is joined to two hydrogen atoms or alkyl groups. the simplest members are cyclopropane (c3h6), cyclobutane (c4h8), cyclohexane (c6h12), and derivatives of these such as methylcyclohexane (c6h11ch3). (from sax, et al., hawley's condensed chemical dictionary, 11th ed)
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 |
|---|---|---|---|---|---|---|
| Cycloalkanes | T52.821 | T52.822 | T52.823 | T52.824 | – | – |
| Cyclohexane | T52.821 | T52.822 | T52.823 | T52.824 | – | – |
| Cycloparaffins | T52.821 | T52.822 | T52.823 | T52.824 | – | – |
| Hexamethylene | T52.821 | T52.822 | T52.823 | T52.824 | – | – |
| Methyl::cyclohexane | T52.821 | T52.822 | T52.823 | T52.824 | – | – |
| Naphthenes | T52.821 | T52.822 | T52.823 | T52.824 | – | – |
Code History & ChangesHistory
New Code T52.821A was added to the ICD-10-CM code set for FY 2027, effective October 1, 2026.
Replacement T52.821A replaces the following previously assigned code(s):
- T52.8X1A - Toxic effect of organic solvents, accidental, init
Questions About T52.821AOverview
Is T52.821A (Toxic effect of cycloparaffins, accidental (unintentional)) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of cycloparaffins, accidental (unintentional), initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character A in T52.821A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for toxic effect of cycloparaffins, accidental (unintentional), such as an emergency visit or first evaluation.
What MS-DRG does T52.821A group to?
When toxic effect of cycloparaffins, accidental (unintentional), initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 918, 917, with relative weights from 0.8716 to 1.5698 depending on complications. Higher weights mean higher Medicare reimbursement.
Can T52.821A be reported with a code from T53?
Not as a rule. The Excludes1 note at T52, which applies to T52.821A, lists "halogen derivatives of aliphatic and aromatic hydrocarbons (T53.-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
