Delayed sleep phase — officially known as delayed sleep-wake phase sleep disorder — is an internal sleep clock (circadian rhythm) sleep disorder in which your sleep pattern is delayed two hours or more from a conventional sleep pattern, causing you to go to sleep later and wake up later.

To diagnose your condition, your doctor may review your family and medical history and conduct a physical examination. Your doctor may order several tests to diagnose your condition or any other related conditions, such as:

• Actigraphy. In this test, you wear a small device that tracks your sleep-wake behavior at home.
• Sleep diary. Your doctor may ask you to keep a sleep diary in which you log your daily sleep and wake times to help show your sleep pattern.
• Polysomnogram. If your doctor suspects you have a different sleep disorder, he or she may order a polysomnogram. In this test, you stay in a sleep center overnight. A polysomnogram monitors your brain activity, heart rate, oxygen levels, eye movements and breathing function as you sleep.

Your doctor will work with you to create a plan for you to treat your condition.

Your plan may include:

• Improving sleep habits. Your doctor may call this sleep hygiene. Good sleep hygiene involves maintaining a regular sleep schedule, avoiding caffeine and stimulating activities near bedtime, avoiding tobacco and alcohol, and only using your bedroom for sleeping and sex. It's also helpful to exercise in the morning, and avoid moderate to vigorous exercise close to bedtime.
• Melatonin supplements. Doctors may prescribe a melatonin supplement to take in the early evening, to help adjust your circadian rhythm.
• Light therapy. Having light exposure in the morning may adjust your internal sleep clock (circadian rhythm).
• Chronotherapy. In chronotherapy, doctors may prescribe you a sleep schedule that delays your bedtime by one to 2.5 hours every six days, until the desired bedtime is reached. You should maintain your sleep schedule once it is established.