T42.1X5 (Adverse effect of iminostilbenes) compared with T42.1X6 (Underdosing of iminostilbenes), from the official CMS tabular data. T42.1X5 and T42.1X6 code the same substance (Carbamazepine) with a different intent.
Same substance, different circumstance of exposure.
Same substance — underdosing (Carbamazepine)
Accidental poisoning, intentional self-harm, assault, undetermined intent, adverse effect and underdosing are mutually exclusive columns — exactly one applies to a given encounter.
Source: CMS Table of Drugs and Chemicals
Same substance, different intent. T42.1X5 and T42.1X6 code the same substance (Carbamazepine) with a different circumstance of exposure.
From the CMS Table of Drugs and Chemicals: accidental poisoning, intentional self-harm, assault, undetermined intent, adverse effect and underdosing are mutually exclusive columns — only one of them applies to a given encounter.
| T42.1X5Adverse effect of iminostilbenes | T42.1X6Underdosing of iminostilbenes | |
|---|---|---|
| Billing status | Non-billable header | 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 | Adverse effect of iminostilbenes is a non-billable ICD-10-CM category code (T42.1X5). | Underdosing of iminostilbenes is a non-billable ICD-10-CM category code (T42.1X6). |
| 7th character | The appropriate 7th character is to be added to each code from category T42 | 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 |
| 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) |
| 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) |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources