Insomnia is not a disease, and no specific test can diagnose it. Your doctor may want to do blood tests to rule out certain medical conditions such as thyroid problems. "Normal sleep" differs for each individual. An evaluation of your health and sleep history is an important first step to finding a cause for poor-quality sleep. Talk with your doctor about your medical history and any current medical problems or medicines you are taking.

• Your doctor can learn a lot about your insomnia and its causes by assessing your sleep history.
• You may be asked to keep a sleep diary for 1 or 2 weeks to document your sleep patterns and related lifestyle factors. See an example of a sleep diary(What is a PDF document?).
• If your symptoms point to mental health concerns, such as depression or anxiety, you may be referred for an assessment by a mental health professional.

If your doctor evaluates your present condition, health, and sleep history and suspects that you may be suffering from certain sleep disorders, you may be referred for a clinical sleep study (polysomnography), in which you sleep overnight in a laboratory. This type of study is sometimes used to assess breathing-related sleep disorders, such as sleep apnea.

A clinical sleep study is not done routinely for insomnia. But it is recommended when:⁷

• Insomnia seems to be caused by sleep-related breathing problems (such as sleep apnea) or periodic limb movement disorder.
• Treatment for insomnia is not working.
• Dangerous behavior occurs during sleep or right after waking up.

Sleep studies are not helpful for investigating insomnia caused by mental health problems, fibromyalgia, or chronic fatigue syndrome.⁷