ICD-10 Code F51.01 – Primary Insomnia (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code F51.01 – Primary insomnia
What it is
Primary insomnia is a sleep disorder in which difficulty falling asleep, staying asleep, or waking too early is not explained by another medical, psychiatric, or substance-related cause.
Clinical signs
Clinical features vary; refer to documentation. Commonly, you may see persistent trouble initiating or maintaining sleep, nonrestorative sleep, and daytime impairment such as fatigue or poor concentration.
When to use this code
Use F51.01 when the provider documents primary insomnia or insomnia disorder as the main diagnosis and does not identify another cause. It is appropriate when the sleep problem is chronic or clinically significant and the record supports a primary sleep disorder.
Apply the code only when the documentation separates insomnia from another condition, such as depression, pain, medication effects, or a substance use disorder. If the cause is unclear, check documentation before coding.
Do not use for
Do not use this code for insomnia due to a medical condition, mental disorder, medication, or substance use. Do not assign it when the chart only mentions poor sleep without a confirmed insomnia diagnosis.
Coding tip
Confirm the provider’s wording and the absence of an underlying cause before assigning F51.01.