G90.81 — Serotonin syndrome
G90.81 is a billable, specific ICD-10-CM code for serotonin syndrome. It is valid for submission on a claim.
Code first
The underlying condition must be sequenced before this code.
- 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
Add a secondary code to capture the detail described below.
- 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-)
Inclusion terms
Alternative wordings a physician may use in the chart for this same code.
- Serotonin toxicity
Risk adjustment
G90.81 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.
Medicare coverage
G90.81 is named in 3 Medicare coverage policies — 3 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.
- A56612Billing and Coding: CT of the Head
- A56771Billing and Coding: Special Electroencephalography
- A57668Billing and Coding: Nerve Conduction Studies and Electromyography
How G90.81 is indexed
Coders do not find codes by browsing the tabular list — they look them up in the alphabetic index, under the word the physician wrote. These are the index entries that lead here, so you can see which chart wordings map to G90.81.
- Syndrome›serotonin
Related codes at this level
Codes that share G90.8. If G90.81 is not quite right, the correct code is usually one of these.
Questions about G90.81
- Is G90.81 a billable ICD-10-CM code?
- Yes. G90.81 is a billable, specific ICD-10-CM code and is valid for submission on a claim.
- Where does G90.81 sit in the tabular list?
- Diseases of the nervous system (G00-G99), in the block Other disorders of the nervous system (G89-G99).