T51.1X4A Toxic effect of methanol, undetermined, initial encounter

ICD-10-CM Diagnosis Code T51.1X4A: Toxic effect of methanol, undetermined, initial encounter

ICD-10-CM code T51.1X4A identifies the toxic effect of methanol when the intent of the injury is undetermined, specifically for an initial encounter. This diagnostic classification belongs to the injury and poisoning code range and captures exposures to nonmedicinal substances where intent remains unknown. 1 2 5

Plain-language overview

The diagnostic entity T51.1X4A denotes a toxic effect of methanol, categorizing the event as an injury or poisoning when the intent behind the exposure remains undetermined. 1 2

What this code represents

Code T51.1X4A represents a toxic effect of methanol with undetermined intent during an initial encounter, functioning as an active terminology concept under the parent code T51.1X4. 1

The sixth character of this code signifies undetermined intent, a designation applied when the intent of the injury is not known or not well documented in the medical record. 2

Coding details

The seventh character A identifies this as an initial encounter, indicating the patient is receiving active treatment for the toxic effect rather than routine recovery care or sequelae. 2

Toxic effects of nonmedicinal substances like methanol are assigned diagnosis codes within the T51 through T65 range rather than separate external cause codes, embedding the mechanism directly into the diagnosis. 2

Documentation considerations

Codes for undetermined intent may be assigned for injury or poisoning events when the intent of the injury is not known or not well documented in the medical record. 2

Coverage and utilization context

State health and violent injury code lists include T51.1X4A alongside other toxic effect codes for substances such as 2-Propanol, though these documents do not explicitly state the codes' reporting requirements. 5 6

What the sources add

While the terminology record defines the code's hierarchical structure, state public documents list T51.1X4A within broader compilations of undetermined overdoses and violent injury codes. 1 5 6

Federal health statistics explain the structural coding rules for embedding intent and encounter type, whereas the terminology record confirms the specific code label and active status. 1 2

Sources

1. ICD-10-CM T51.1X4A terminology record — National Cancer Institute Enterprise Vocabulary Services; accessed 2026-07-27.
2. National Health Statistics Reports — cdc.gov; accessed 2026-07-27.
3. ACMT 2019 Annual Scientific Meeting Abstracts—San Francisco, CA — pmc.ncbi.nlm.nih.gov; accessed 2026-07-27.
4. Toxicological profile for methylene chloride — atsdr.cdc.gov; accessed 2026-07-27.
5. ICD 10 codes for reportable Undetermined overdoses — hhs.nd.gov; accessed 2026-07-27.
6. Violent Injury ICD-10 Inclusion Codes — dph.illinois.gov; accessed 2026-07-27.