A careful history will usually help diagnose insomnia. Maintaining a sleep diary for two weeks will provide additional information. Here a record is made of when the person goes to sleep and when he wakes up, along with how long he is awake during the night. The sleep diary will help the doctor understand the patient's sleeping pattern.
Epworth sleepiness scale is a questionnaire filled out by the patient, estimating the likelihood of falling asleep in different situations. This permits a standardized subjective assessment of daytime sleepiness, which is an indicator of insomnia.
Polysomnogram is an over night sleep study, which can be undertaken to rule out other sleep disorders.