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ICD10BillableValid for clinical use

ICD-10 Code G90.81: Serotonin syndrome

G90.81 is a billable ICD-10 diagnosis code used to classify Serotonin syndrome in medical records and claims. You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records. ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Diseases of the nervous system (G00-G99).

What is this code?

ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Diseases of the nervous system (G00-G99).

When is it used?

  • May be used when a clinician documents serotonin syndrome in a patient's medical record.
  • May appear in hospital records, claims, referrals, and clinical documentation.
  • This code can be used as a clinically usable diagnosis entry in standardized coding workflows.

What it does not mean

  • A code alone does not explain severity, treatment plan, or outcome.
  • A medical code should not be treated as a substitute for a doctor's diagnosis or advice.

Code hierarchy

chapter
6Diseases of the nervous system (G00-G99)
block
G89-G99Other disorders of the nervous system
category
G90Disorders of autonomic nervous system
category
G90.8Other disorders of autonomic nervous system
currentG90.8

Official coding notes

Inclusion terms
  • Serotonin toxicity
Applicable to
  • code for adverse effect, if applicable, to identify drug, such as:
  • linezolid (T36.8X5)
  • monoamine oxidase inhibitors (T43.1X5)
  • selective serotonin and norepinephrine reuptake inhibitors [SSNRI] (T43.215)
  • selective serotonin reuptake inhibitors [SSRI] (T43.225)
  • code, if applicable, to identify:
  • disseminated intravascular coagulation (D65)
  • hypertensive crisis (I16.-)
  • metabolic acidosis (E87.2-)
  • shock, not elsewhere classified (R57.-)
  • toxic encephalopathy (G92.-)
  • ventricular tachycardia (I47.2-)
  • poisoning due to drug or toxin, such as:
  • linezolid (T36.8X- with sixth character 1-4)
  • monoamine oxidase inhibitors (T43.1X with sixth character 1-4)
  • selective serotonin and norepinephrine reuptake inhibitors [SSNRI] (T43.21 with sixth character 1-4)
  • selective serotonin reuptake inhibitors [SSRI] (T43.22 with sixth character 1-4)
Code first
  • poisoning due to drug or toxin, such as:
  • linezolid (T36.8X- with sixth character 1-4)
  • monoamine oxidase inhibitors (T43.1X with sixth character 1-4)
  • selective serotonin and norepinephrine reuptake inhibitors [SSNRI] (T43.21 with sixth character 1-4)
  • selective serotonin reuptake inhibitors [SSRI] (T43.22 with sixth character 1-4)
Use additional code
  • code for adverse effect, if applicable, to identify drug, such as:
  • linezolid (T36.8X5)
  • monoamine oxidase inhibitors (T43.1X5)
  • selective serotonin and norepinephrine reuptake inhibitors [SSNRI] (T43.215)
  • selective serotonin reuptake inhibitors [SSRI] (T43.225)
  • code, if applicable, to identify:
  • disseminated intravascular coagulation (D65)
  • hypertensive crisis (I16.-)
  • metabolic acidosis (E87.2-)
  • shock, not elsewhere classified (R57.-)
  • toxic encephalopathy (G92.-)
  • ventricular tachycardia (I47.2-)

Where you may see this code

You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records.

Related specialists

NeurologistGeneral Physician

Coverage-related procedures and services

CPT 70460high
COMPUTED TOMOGRAPHY, HEAD OR BRAIN; WITH CONTRAST MATERIAL(S)
Source: CMS coverage guidance
CPT 70450high
COMPUTED TOMOGRAPHY, HEAD OR BRAIN; WITHOUT CONTRAST MATERIAL
Source: CMS coverage guidance
CPT 70470high
COMPUTED TOMOGRAPHY, HEAD OR BRAIN; WITHOUT CONTRAST MATERIAL, FOLLOWED BY CONTRAST MATERIAL(S) AND FURTHER SECTIONS
Source: CMS coverage guidance
HCPCS G0255high
CURRENT PERCEPTION THRESHOLD/SENSORY NERVE CONDUCTION TEST, (SNCT) PER LIMB, ANY NERVE
Source: CMS coverage guidance
CPT 95873high
ELECTRICAL STIMULATION FOR GUIDANCE IN CONJUNCTION WITH CHEMODENERVATION (LIST SEPARATELY IN ADDITION TO CODE FOR PRIMARY PROCEDURE)
Source: CMS coverage guidance
CPT 95700high
ELECTROENCEPHALOGRAM (EEG) CONTINUOUS RECORDING, WITH VIDEO WHEN PERFORMED, SETUP, PATIENT EDUCATION, AND TAKEDOWN WHEN PERFORMED, ADMINISTERED IN PERSON BY EEG TECHNOLOGIST, MINIMUM OF 8 CHANNELS
Source: CMS coverage guidance

Coding guidelines

Common synonyms

Serotonin syndrome

Frequently asked questions

Code details

CodeG90.81
SystemICD10
Display nameSerotonin syndrome
ChapterDiseases of the nervous system (G00-G99)
BlockOther disorders of the nervous system

Flags

BillableYes
Valid clinical useYes

Source

SourceICD-10
Version2026-annual
Releaseannual
Year2026

Index terms

Matched terms
Syndrome

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.