ICD-10-CM 2027
ICD-10 code for serotonin syndrome
From the official ICD-10-CM alphabetic index entry “Syndrome › serotonin”. Page updated September 29, 2026.
About coding serotonin syndrome
The ICD-10-CM code for serotonin syndrome is G90.81 (Serotonin syndrome).
Within G90.8 (other disorders of autonomic nervous system), G90.81 is specifically for serotonin syndrome. Related codes cover other disorders of autonomic nervous system (G90.89).
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) and selective serotonin reuptake inhibitors [SSRI] (T43.22 with sixth character 1-4).
Use an additional 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) and selective serotonin reuptake inhibitors [SSRI] (T43.225). Use an additional code, if applicable, to identify: disseminated intravascular coagulation (D65), hypertensive crisis (I16.-), metabolic acidosis (E87.2-), shock, not elsewhere classified (R57.-), toxic encephalopathy (G92.-) and 1 more.
Common questions about serotonin syndrome ICD-10 codes
What is the ICD-10 code for serotonin syndrome?
- G90.81 — Serotonin syndrome.
Is G90.81 billable?
- Yes. G90.81 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can G90.81 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict G90.81 as a principal diagnosis.
Is G90.81 a CC or MCC?
- No. G90.81 is neither a CC nor an MCC under MS-DRG v44.0.