ICD-10 Code F51.09 – Other insomnia not due to a substance or known physiological condition (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code F51.09 – Other insomnia not due to a substance or known physiological condition
What it is
Use this code for insomnia that is not explained by a substance, medication, or a known medical condition. It describes sleep difficulty such as trouble falling asleep, staying asleep, or waking too early.
Clinical signs
Clinical features vary; refer to documentation. Commonly recorded findings include persistent sleep disturbance, daytime fatigue, poor concentration, and distress or impaired functioning related to inadequate sleep.
When to use this code
Use F51.09 when the record documents insomnia and the clinician does not link it to alcohol, drugs, medications, or a physiological disorder. It may fit cases labeled as other insomnia, atypical insomnia, or insomnia NOS when the cause remains unclear. Check documentation if the note suggests another primary sleep disorder.
Do not use for
Do not use this code when insomnia is caused by a substance, medication, or an identified medical condition. If the chart supports a specific sleep disorder or another documented cause, code that condition instead.
Coding tip
Assign this code only after the provider rules out substance-related and physiological causes in the documentation.