2026 ICD-10-CM Diagnosis Code T88.3XXAMalignant hyperthermia due to anesthesia, initial encounter

ICD-10-CM Codes›S00–T88›T80-T88›T88

ICD-10-CM T88.3XXA
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T88.3XXA is a billable ICD-10-CM diagnosis code for malignant hyperthermia due to anesthesia, 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 922 through 923. Coders also document this condition as drug-induced hyperpyrexia. 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
T88.3XXA
Billable Status
Yes — Valid for Submission
Code Describes
Malignant hyperthermia due to anesthesia, initial encounter
Short Description
Malignant hyperthermia due to anesthesia, initial encounter
Same as the full description in the CMS dataset.
Parent Code
T88.3
Malignant hyperthermia due to anesthesia

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 CodeT88.3XXAMalignant hyperthermia due to anesthesia, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Drug-induced hyperpyrexia
  • Hyperpyrexia
  • Malignant hyperthermia
  • Malignant hyperthermia caused by anesthetic

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

Clinical InformationClinical

  • Malignant Hyperthermia

    rapid and excessive rise of temperature accompanied by muscular rigidity following general anesthesia.

  • Hyperpyrexia

    body temperature of 106 degrees fahrenheit (41.1 degrees celsius) or higher.

  • Malignant Hyperthermia Syndrome|Malignant Hyperpyrexia|Malignant Hyperthermia|Malignant Hyperthermia

    a rare disorder characterized by rapid rise of the body temperature, accompanied by rhabdomyolysis and, if untreated, by collapse and death. it occurs in susceptible individuals who receive certain drugs for general anesthesia, gas anesthetics, or succinylcholine. it may be inherited in an autosomal dominant pattern.

Patient EducationClinical

Anesthesia

Anesthesia is the use of medicines, called anesthetics, to prevent pain during surgery and other medical procedures. Medicine may be given by injection, inhalation, topical lotion, spray, eye drops, or a skin patch.

The full article covers:

  • What is anesthesia?
  • What is anesthesia used for?
  • What are the types of anesthesia?
  • What are the risks of anesthesia?

Read the full article at MedlinePlus

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

Convert T88.3XXA to ICD-9-CMHistory

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

ICD-9-CM
995.86 Malignant hyperthermia
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 T88.3XXAOverview

Is T88.3XXA (Malignant hyperthermia due to anesthesia) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report malignant hyperthermia due to anesthesia, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in T88.3XXA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for malignant hyperthermia due to anesthesia, such as an emergency visit or first evaluation.

What MS-DRG does T88.3XXA group to?

When malignant hyperthermia due to anesthesia, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of T88.3XXA?

Under the General Equivalence Mappings, malignant hyperthermia due to anesthesia, initial encounter converts to ICD-9-CM 995.86 (malignant hyperthermia). 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.