2026 ICD-10-CM Diagnosis Code T65.822AToxic effect of harmful algae and algae toxins, intentional self-harm, initial encounter

ICD-10-CM Codes›S00–T88›T51-T65›T65

ICD-10-CM T65.822A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T65.822A is a billable ICD-10-CM diagnosis code for toxic effect of harmful algae and algae toxins, intentional self-harm, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 917 through 918. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, self-harm; External cause codes: natural/environment; initial encounter; and Suicidal ideation/attempt/intentional self-harm.

Code Identity

ICD-10-CM Code
T65.822A
Billable Status
Yes — Valid for Submission
Code Describes
Toxic effect of harmful algae and algae toxins, intentional self-harm, initial encounter
Short Description
Toxic eff of harmful algae and algae toxins, slf-hrm, init
Parent Code
T65.822
Toxic effect of harmful algae and algae toxins, intentional self-harm

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT51-T65Toxic effects of substances chiefly nonmedicinal as to source
CategoryT65Toxic effect of other and unspecified substances
This CodeT65.822AToxic effect of harmful algae and algae toxins, intentional self-harm, initial encounter

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Toxic effect of other and unspecified substances (T65). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR EXT021
External cause codes: intent of injury, self-harm
Default principal diagnosis: inpatient No · outpatient No
CCSR EXT011
External cause codes: natural/environment; initial encounter
Default principal diagnosis: inpatient No · outpatient No
CCSR MBD012
Suicidal ideation/attempt/intentional self-harm
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INJ023
Toxic effects, initial encounter
Default principal diagnosis: inpatient No · outpatient No

Table of Drugs and ChemicalsClinical

Substances in the Table of Drugs and Chemicals that reference this code family. Always confirm in the Tabular List before coding.

SubstanceAccidentalSelf-harmAssaultUndeter­minedAdverse
Effect		Under­dosing
Algae (harmful) (toxin)T65.821T65.822T65.823T65.824––

Convert T65.822A to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
989.89 Tox eff nonmed subst NEC
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.
ICD-9-CM
E950.9 Poison-solid/liquid NEC
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About T65.822AOverview

Is T65.822A a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of harmful algae and algae toxins, intentional self-harm, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in T65.822A mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for toxic effect of harmful algae and algae toxins, intentional self-harm, such as an emergency visit or first evaluation.

What MS-DRG does T65.822A group to?

When toxic effect of harmful algae and algae toxins, intentional self-harm, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of T65.822A?

Under the General Equivalence Mappings, toxic effect of harmful algae and algae toxins, intentional self-harm, initial encounter converts to ICD-9-CM 989.89 (tox eff nonmed subst NEC) and E950.9 (poison-solid/liquid NEC). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.