T42 vs T42-T43
T42 (Poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs) compared with T42-T43 (Anticonvulsants & Psychotropics (T42-T43)), from the official CMS tabular data.
Summary
These codes represent different levels of the same hierarchy: T42 is the non-billable header that contains T42-T43, so only T42-T43 (or a sibling) is reported.
Registry fact- What is different?
The conditions named.T42 is “Poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs”; T42-T43 is “Anticonvulsants & Psychotropics (T42-T43)”.
Registry fact
- Can these codes be reported together?
Not as a pair.T42 is the non-billable header that contains T42-T43. A header is not reported on a claim, so the choice is T42-T43 or a sibling that matches the documentation.
Registry fact
- Is there an Excludes1 relationship?
None.Neither entry carries an Excludes1 note that names the other code. T42 carries 1 Excludes1 note and T42-T43 carries 1 Excludes1 note covering other codes; the side-by-side table quotes them.
Official rule
- Is there an Excludes2 relationship?
None.Neither entry carries an Excludes2 note that names the other code. T42 carries 6 Excludes2 notes and T42-T43 carries 5 Excludes2 notes covering other codes; the side-by-side table quotes them.
Official rule
- Is one more specific?
Yes.T42-T43 is a subdivision of T42 in the tabular hierarchy, so it is the more specific of the two.
Registry fact
- Is one a parent or header code?
Yes.T42 is the non-billable header that contains T42-T43. A header stands for the whole family beneath it and is not reported on a claim.
Registry fact
- Are there sequencing instructions?
None.Neither entry carries a Code First or Use Additional Code note that names the other.
Official rule
- Are there other coding relationships?
None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.
MedCoder-derived
Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels
Can these codes be reported together?
Not as a pair — T42 is not reportable. T42 is the non-billable category that contains T42-T43.
A header stands for the whole family of codes beneath it and is not reported on a claim, so the choice is T42-T43 or a sibling that matches the documentation. No Excludes1/Excludes2 relationship exists between these codes in the official tabular list.
Official guidance behind these answers
Section I.B.2 — Level of Detail in Coding · applies to: T42 and T42-T43
Diagnosis codes are to be used and reported at their highest number of characters available and to the highest level of specificity documented in the medical record. ICD-10-CM diagnosis codes are composed of codes with 3, 4, 5, 6 or 7 characters. Codes with three characters are included in ICD-10-CM as the heading of a category of codes that may be further subdivided by the use of fourth and/or fifth characters and/or sixth characters, which provide greater detail. A three-character code is to be used only if it is not further subdivided. A code is invalid if it has not been coded to the full number of characters required for that code, including the 7th character, if applicable.
ICD-10-CM Official Guidelines FY2026
Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum
Side by side
| T42Poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs | T42-T43Anticonvulsants & Psychotropics (T42-T43) | |
|---|---|---|
| Billing status | Non-billable header Report instead: T42.0X1A, T42.0X1D, T42.0X1S, T42.0X2A, T42.0X2D | Non-billable header |
| Classification | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) |
| Definition | Poisoning by, adverse effect of and underdosing of antiepileptic, sedative- hypnotic and antiparkinsonism drugs is a non-billable ICD-10-CM category code (T42). | Anticonvulsants & Psychotropics (T42-T43) is a non-billable ICD-10-CM category code (T42-T43). |
| 7th character | The appropriate 7th character is to be added to each code from category T42 | — |
| Includes | adverse effect of correct substance properly administered poisoning by overdose of substance poisoning by wrong substance given or taken in error underdosing by (inadvertently) (deliberately) taking less substance than prescribed or instructed | adverse effect of correct substance properly administered poisoning by overdose of substance poisoning by wrong substance given or taken in error underdosing by (inadvertently) (deliberately) taking less substance than prescribed or instructed |
| Excludes1 | toxic reaction to local anesthesia in pregnancy (O29.3-) | toxic reaction to local anesthesia in pregnancy (O29.3-) |
| Excludes2 | drug dependence and related mental and behavioral disorders due to psychoactive substance use (F10.--F19.-) abuse and dependence of psychoactive substances (F10-F19) abuse of non-dependence-producing substances (F55.-) immunodeficiency due to drugs (D84.821) drug reaction and poisoning affecting newborn (P00-P96) pathological drug intoxication (inebriation) (F10-F19) | abuse and dependence of psychoactive substances (F10-F19) abuse of non-dependence-producing substances (F55.-) immunodeficiency due to drugs (D84.821) drug reaction and poisoning affecting newborn (P00-P96) pathological drug intoxication (inebriation) (F10-F19) |
| Code first | , for adverse effects, the nature of the adverse effect, such as: adverse effect NOS (T88.7) | , for adverse effects, the nature of the adverse effect, such as: adverse effect NOS (T88.7) |
| Use additional code | code(s) to specify: manifestations of poisoning underdosing or failure in dosage during medical and surgical care (Y63.6, Y63.8-Y63.9) | code(s) to specify: manifestations of poisoning underdosing or failure in dosage during medical and surgical care (Y63.6, Y63.8-Y63.9) |
Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on.
Derived from the official CMS ICD-10-CM tabular data (FY2027). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources