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T42.1 vs T42.6X2

T42.1 (Poisoning by, adverse effect of and underdosing of iminostilbenes) compared with T42.6X2 (Poisoning by other antiepileptic and sedative-hypnotic drugs, intentional self-harm), from the official CMS tabular data.

Summary

These codes should not be reported together because T42.6X2’s tabular entry lists T42.1 under Excludes1.

Official rule
What is different?

Title wording.The titles share “Poisoning by”; T42.1 says “adverse effect of and underdosing of iminostilbenes” where T42.6X2 says “other antiepileptic and sedative-hypnotic drugs, intentional self-harm”.

Registry fact

Can these codes be reported together?

No.T42.6X2’s entry carries an Excludes1 note covering T42.1: “poisoning by, adverse effect of and underdosing of carbamazepine (T42.1-)”. Both may be reported only when the documentation shows the two conditions are unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes1 relationship?

Yes.T42.6X2’s tabular entry: “poisoning by, adverse effect of and underdosing of carbamazepine (T42.1-)”. The note covers T42.1.

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes2 relationship?

None.Neither entry carries an Excludes2 note that names the other code. T42.1 carries 6 Excludes2 notes and T42.6X2 carries 6 Excludes2 notes covering other codes; the side-by-side table quotes them.

Official rule

Is one more specific?

No.Neither is a subdivision of the other, and neither title is the unspecified form; they describe different conditions within category T42.

Registry fact

Is one a parent or header code?

Both are headers.Both are non-billable headers, and neither contains the other.

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?

Conflict

Excludes1 conflict

T42.6X2
Poisoning by other antiepileptic and sedative-hypnotic drugs, intentional self-harm
↔
T42.1
Poisoning by, adverse effect of and underdosing of iminostilbenes

What we found

No — do not report together.T42.6X2 carries an Excludes1 note covering T42.1: “poisoning by, adverse effect of and underdosing of carbamazepine (T42.1-)”

Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

What to review

Report one of the two. Both may be reported only when the documentation shows the two conditions are unrelated to each other.

Guide: Excludes1 vs Excludes2Check these on a claim

Why it matters

An Excludes1 note means the two conditions cannot occur together, so the pair should not be reported for the same encounter. The sole exception is when the conditions are documented as unrelated to each other.

Source / rule

CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a

Official guidance behind these answers

  • Section I.A.12.a — Excludes1 · applies to: Excludes1

    A type 1 Excludes note is a pure excludes note. It means “NOT CODED HERE!” An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition. An exception to the Excludes1 definition is the circumstance when the two conditions are unrelated to each other. If it is not clear whether the two conditions involving an Excludes1 note are related or not, query the provider. For example, code F45.8, Other somatoform disorders, has an Excludes1 note for "sleep related teeth grinding (G47.63)," because "teeth grinding" is an inclusion term under F45.8. Only one of these two codes should be assigned for teeth grinding. However psychogenic dysmenorrhea is also an inclusion term under F45.8, and a patient could have both this condition and sleep related teeth grinding. In this case, the two conditions are clearly unrelated to each other, and so it would be appropriate to report F45.8 and G47.63 together.

    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

T42.1Poisoning by, adverse effect of and underdosing of iminostilbenesT42.6X2Poisoning by other antiepileptic and sedative-hypnotic drugs, intentional self-harm
Billing statusNon-billable header

Report instead: T42.1X1A, T42.1X1D, T42.1X1S, T42.1X2A, T42.1X2D

Non-billable header

Report instead: T42.6X2A, T42.6X2D, T42.6X2S

ClassificationS00-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)
DefinitionPoisoning by, adverse effect of and underdosing of iminostilbenes is a non-billable ICD-10-CM category code (T42.1).Poisoning by other antiepileptic and sedative-hypnotic drugs, intentional self-harm is a non-billable ICD-10-CM category code (T42.6X2).
7th characterThe appropriate 7th character is to be added to each code from category T42The 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-)
poisoning by, adverse effect of and underdosing of carbamazepine (T42.1-)
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)
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)
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.

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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