G90.81 – Serotonin syndrome

ICD-10-CM 2027 diagnosis code · Other disorders of the nervous system

Billable code

ICD-10-CM code G90.81

Code: G90.81 (claims format: G9081)
Description: Serotonin syndrome
Billable: Yes – valid for HIPAA-covered transactions
Valid for: Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter: 6. Diseases of the nervous system (G00-G99)
Block: G89-G99 Other disorders of the nervous system
Parent codes: G90 › G90.8

Notes for G90.81

Applicable to:

Serotonin toxicity

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-)

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

G90 – Disorders of autonomic nervous system

Excludes1 (not coded here):

dysfunction of the autonomic nervous system due to alcohol (G31.2)

Index terms for G90.81

Entries in the ICD-10-CM alphabetic index that lead to this code:

Syndrome, serotonin

Related codes in G90.8

G90.89 – Other disorders of autonomic nervous systemBillable

Frequently asked questions

What is ICD-10 code G90.81?

G90.81 is the ICD-10-CM code for serotonin syndrome, in the block G89-G99 (Other disorders of the nervous system).

Is G90.81 a billable code?

Yes. G90.81 is a billable/specific code that can be used to indicate a diagnosis for reimbursement purposes.

What category does G90.81 belong to?

It belongs to category G90 – Disorders of autonomic nervous system.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.