2026 ICD-10-CM Diagnosis Code T43.655AAdverse effect of methamphetamines, initial encounter

ICD-10-CM Codes›S00–T88›T36-T50›T43

ICD-10-CM T43.655A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T43.655A is a billable ICD-10-CM diagnosis code for adverse effect of methamphetamines, 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. The code is not accepted as a principal diagnosis by the Medicare Code Editor. Coders also document this condition as adverse reaction caused by methamphetamine. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Adverse effects of drugs and medicaments, initial encounter; and Stimulant-related disorders.

Code Identity

ICD-10-CM Code
T43.655A
Billable Status
Yes — Valid for Submission
Code Describes
Adverse effect of methamphetamines, initial encounter
Short Description
Adverse effect of methamphetamines, initial encounter
Same as the full description in the CMS dataset.
Parent Code
T43.655
Adverse effect of methamphetamines

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT36-T50Poisoning by, adverse effect of and underdosing of drugs, medicaments and biological substances
CategoryT43Poisoning by, adverse effect of and underdosing of psychotropic drugs, not elsewhere classified
This CodeT43.655AAdverse effect of methamphetamines, initial encounter

Code EditsBilling

Medicare Code Editor checks that affect claim validity for T43.655A.

Unacceptable principal diagnosis
There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Adverse reaction caused by methamphetamine
  • Amphetamine group adverse reaction

Coding GuidelinesGuidance

When coding an adverse effect of a drug that has been correctly prescribed and properly administered, assign the appropriate code for the nature of the adverse effect followed by the appropriate code for the adverse effect of the drug.

The appropriate 7th character is to be added to each code from block Poisoning by, adverse effect of and underdosing of psychotropic drugs, not elsewhere classified (T43). 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 INJ028
Adverse effects of drugs and medicaments, initial encounter
Default principal diagnosis: inpatient No · outpatient Yes
CCSR MBD021
Stimulant-related disorders
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Methamphetamine

    a central nervous system stimulant and sympathomimetic with actions and uses similar to dextroamphetamine. the smokable form is a drug of abuse and is referred to as crank, crystal, crystal meth, ice, and speed.

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
DesoxyephedrineT43.651T43.652T43.653T43.654T43.655T43.656
MetamfetamineT43.651T43.652T43.653T43.654T43.655T43.656
MethamphetamineT43.651T43.652T43.653T43.654T43.655T43.656
MethedrineT43.651T43.652T43.653T43.654T43.655T43.656
MethylamphetamineT43.651T43.652T43.653T43.654T43.655T43.656
SpeedT43.651T43.652T43.653T43.654T43.655T43.656

Code History & ChangesHistory

Replacement T43.655A replaces the following previously assigned code(s):

  • T43.625A - Adverse effect of amphetamines, initial encounter
FY 2023AddedAdded to the ICD-10-CM code setEffective October 1, 2022.
FY 2024–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About T43.655AOverview

Is T43.655A (Adverse effect of methamphetamines) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report adverse effect of methamphetamines, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in T43.655A mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for adverse effect of methamphetamines, such as an emergency visit or first evaluation.

What MS-DRG does T43.655A group to?

On inpatient claims, adverse effect of methamphetamines, initial encounter maps to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.

Can T43.655A be a principal diagnosis?

No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of methamphetamines, initial encounter describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.

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.