2026 ICD-10-CM Diagnosis Code T88.7XXAUnspecified adverse effect of drug or medicament, initial encounter

ICD-10-CM Codes›S00–T88›T80-T88›T88

ICD-10-CM T88.7XXA
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T88.7XXA is a billable ICD-10-CM diagnosis code for unspecified adverse effect of drug or medicament, 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 919 through 921. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Complication of other surgical or medical care, injury, initial encounter.

Code Identity

ICD-10-CM Code
T88.7XXA
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified adverse effect of drug or medicament, initial encounter
Short Description
Unsp adverse effect of drug or medicament, init encntr
Parent Code
T88.7
Unspecified adverse effect of drug or medicament

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT80-T88Complications of surgical and medical care, not elsewhere classified
CategoryT88Other complications of surgical and medical care, not elsewhere classified
This CodeT88.7XXAUnspecified adverse effect of drug or medicament, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Adverse drug interaction
  • Adverse medication interaction with alcohol
  • Adverse medication interaction with food
  • Adverse medication interaction with medication
  • Chemotherapy-induced nausea and vomiting
  • Drug interaction with alcohol
  • Drug interaction with drug
  • Drug-induced personality disorder
  • Fixed drug reaction
  • Medication interaction
  • Medication interaction potentiation
  • Medication interaction with food
  • Multiple drug hypersensitivity syndrome
  • Nausea and vomiting
  • Non-allergic drug hypersensitivity disorder
  • Phototoxicity

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Other complications of surgical and medical care, not elsewhere classified (T88). 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 INJ037
Complication of other surgical or medical care, injury, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Drug Reactions

Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions, such as drug interactions, side effects, and allergies.

The full article covers:

  • What is a drug interaction?
  • What are side effects?
  • What are drug allergies?
  • How can I stay safe when taking medicines?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert T88.7XXA to ICD-9-CMHistory

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

ICD-9-CM
999.9 Complic med care NEC/NOS
Approximate The match is approximate rather than exact.

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 T88.7XXAOverview

Is T88.7XXA (Unspecified adverse effect of drug or medicament) a billable code?

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

What does the 7th character A in T88.7XXA mean?

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

What MS-DRG does T88.7XXA group to?

When unspecified adverse effect of drug or medicament, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 919, 920, 921, with relative weights from 0.6884 to 1.8308 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of T88.7XXA?

Under the General Equivalence Mappings, unspecified adverse effect of drug or medicament, initial encounter converts to ICD-9-CM 999.9 (complic med care NEC/NOS). 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.