ICD-10 Code G47.21 – Circadian rhythm sleep disorder, delayed sleep phase type (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G47.21 – Circadian rhythm sleep disorder, delayed sleep phase type
What it is
G47.21 identifies a circadian rhythm sleep disorder in which the patient’s sleep schedule is delayed relative to the desired or socially required time. Sleep onset and wake time occur later than expected, causing difficulty falling asleep and waking on time.
Clinical signs
Typical findings include persistent late sleep onset, trouble waking for school or work, and better sleep when allowed to follow a delayed schedule. Clinical features vary; refer to documentation.
When to use this code
Use this code when the provider documents delayed sleep phase type circadian rhythm sleep disorder, delayed sleep-wake phase disorder, or an equivalent diagnosis. Apply it when the main problem is a stable shift in sleep timing, not simple insomnia. Confirm the chart supports a circadian rhythm disorder rather than another sleep condition.
Do not use for
Do not use this code for general insomnia, poor sleep hygiene, or sleep loss from shift work unless the provider specifically documents delayed sleep phase type. Check documentation if the sleep complaint is better explained by another disorder.
Coding tip
Code only when the delayed phase diagnosis is clearly stated; if the wording is vague, query the provider for clarification.