Q&A: ICD-10-CM coding for poisoning with resulting manifestations

Q: What is the correct ICD-10-CM coding approach for poisoning cases that include documented manifestations, and how are these cases reflected in code selections and sequencing?

A: Let’s look at two examples of poisoning, one accidental and the other intentional self-harm, to understand the best approach for coding poisonings with manifestations.

First consider a patient who accidentally takes double the prescribed dose of amitriptyline, a generic prescription classified as a tricyclic antidepressant. Not taking their medication exactly as prescribed causes the patient to feel dizzy and confused. This scenario is classified as a poisoning because the drug was taken incorrectly (i.e., wrong dose), even though the intent was not malicious. ICD-10-CM codes for poisonings are found in categories T36-T50 and are reported first, followed by codes for any resulting clinical manifestations. The code must specify the intent with fifth/sixth character 1, 2, 3, or 4, depending on whether it is accidental, intentional, assault, or undetermined. The intent in this scenario is accidental, so the sixth character would be 1. If the intent was unclear, coders would need to query the provider to avoid making assumptions.

Because a wide variety of medications, illicit substances, and chemicals can be associated with poisoning, it is not practical for the ICD-10-CM Alphabetic Index to list each drug in depth. As a result, many substances are either listed in a limited manner or not individually detailed within the main index entries for the intent. Coders must therefore consult the ICD-10-CM Table of Drugs and Chemicals, which systemically organizes substances by name and identifies the appropriate subcategories based on intent. Locating antidepressant followed by tricyclic leads to a row of subcategories found under T43.01-. The subcategory listed under unintentional poisoning is T43.011-, where the seventh character would be A to represent the initial encounter. All poisoning codes require a seventh character to indicate the encounter type.

Codes for dizziness and disorientation are coded as secondary diagnoses. According to the 2026 ICD-10-CM Alphabetic Index, dizziness is reported with R42, and disorientation is reported with R41.0.

Now consider a teenager who ingests a full bottle of ibuprofen in a suicide attempt, resulting in acute kidney injury. When a poisoning is intentional, it should be classified as a self-harm poisoning, and the external cause must be clearly documented, else the coder will need to query for further clarification. The poisoning is again sequenced first. Ibuprofen is classified as a propionic acid derivative, but the medication is listed as its own substance in the Table of Drugs and Chemicals. The row of subcategories for ibuprofen are under T39.31-. The subcategory listed under intentional self-harm poisoning is T39.312-, where the seventh character would be A to represent the initial encounter.

The secondary code for this scenario would be for acute kidney failure. Looking up “Failure, renal, acute” in the alphabetic index, coders will find N17.9 (acute kidney failure, unspecified) as the assignable code.

Editor’s note: This Q&A originally appeared in JustCoding. It was answered in an HCPro webinar, “Beyond the Bottle: ICD-10-CM Coding Poisoning, Adverse Effects, and Underdosing with Accuracy and Clarity,” presented by Leigh Poland, RHIA, CCS, CDIP, CIC, vice president of coding services at AGS Health.