G90.81
Serotonin syndrome
Billable FY2026 2025-10-01 → 2026-09-30
FY2025–2027 only
Exclusions 9 never code together
G00-G99chapter
Excludes2
- certain conditions originating in the perinatal period (P04-P96)P04-P96
- certain infectious and parasitic diseases (A00-B99)A00-B99
- complications of pregnancy, childbirth and the puerperium (O00-O9A)O00-O9A
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Q00-Q99
- endocrine, nutritional and metabolic diseases (E00-E88)E00-E88
- injury, poisoning and certain other consequences of external causes (S00-T88)S00-T88
- neoplasms (C00-D49)C00-D49
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)R00-R94
Excludes1 — never code together. The excluded condition and this one are mutually exclusive.
Excludes2 — not included here, but the patient may have both. Code both when documented.
Instructional notes 18
G90.81code
Inclusion terms
- Serotonin toxicity
Code first
- poisoning due to drug or toxin, such as:
- linezolid (T36.8X- with sixth character 1-4)T36.8X-
- monoamine oxidase inhibitors (T43.1X with sixth character 1-4)T43.1X
- selective serotonin and norepinephrine reuptake inhibitors [SSNRI] (T43.21 with sixth character 1-4)T43.21
- selective serotonin reuptake inhibitors [SSRI] (T43.22 with sixth character 1-4)T43.22
Use additional code
- code for adverse effect, if applicable, to identify drug, such as:
- linezolid (T36.8X5)T36.8X5
- monoamine oxidase inhibitors (T43.1X5)T43.1X5
- selective serotonin and norepinephrine reuptake inhibitors [SSNRI] (T43.215)T43.215
- selective serotonin reuptake inhibitors [SSRI] (T43.225)T43.225
- code, if applicable, to identify:
- disseminated intravascular coagulation (D65)D65
- hypertensive crisis (I16.-)I16.-
- metabolic acidosis (E87.2-)E87.2-
- shock, not elsewhere classified (R57.-)R57.-
- toxic encephalopathy (G92.-)G92.-
- ventricular tachycardia (I47.2-)I47.2-
Index entries leading here 1
- Syndrome — see also Disease
- serotonin G90.81
Alongside this code 1 same parent — G90.8
Additional references
AHA Coding Clinic® Licence required
Official coding advice for this code. Published by the American Hospital Association. Not included in this installation.