G90.81 Serotonin syndrome

Billable ICD-10-CM code, FY2026.

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-)

Applies from G90 Disorders of autonomic nervous system

Excludes1 (never code together)

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

MS-DRG index

Defines the logic of DRG(s) 073-074 in MDC 01.

Diagnosis Index entries for G90.81

• Syndrome › serotonin

Nearby codes

• G90.522 Complex regional pain syndrome I of left lower limb
• G90.523 Complex regional pain syndrome I of lower limb, bilateral
• G90.529 Complex regional pain syndrome I of unspecified lower limb
• G90.59 Complex regional pain syndrome I of other specified site
• G90.8 Other disorders of autonomic nervous system
• G90.81 Serotonin syndrome (this code)
• G90.89 Other disorders of autonomic nervous system
• G90.9 Disorder of the autonomic nervous system, unspecified
• G90.A Postural orthostatic tachycardia syndrome [POTS]
• G90.B LMNB1-related autosomal dominant leukodystrophy