ICD-10 Code F51.13 – Hypersomnia due to other mental disorder (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code F51.13 – Hypersomnia due to other mental disorder
What it is
This code identifies hypersomnia that is caused by, or occurs with, another mental disorder. Use it when excessive sleepiness is documented as part of a psychiatric condition rather than a primary sleep disorder.
Clinical signs
Patients may report prolonged sleep time, repeated daytime sleep episodes, or marked difficulty staying awake. Clinical features vary; refer to documentation, and confirm the mental disorder link is stated clearly.
When to use this code
Use F51.13 when the record shows hypersomnia is secondary to a mental disorder such as depression or another psychiatric diagnosis. You should code it when the provider documents the relationship, not when sleepiness is unexplained.
Do not use for
Do not use this code for primary hypersomnia, narcolepsy, or sleepiness due to medications, substances, or medical illness. Check documentation if the cause is not clearly tied to a mental disorder.
Coding tip
Verify that the mental disorder and the causal link to hypersomnia are both documented before assigning F51.13.