Multiple Sleep Latency Testing is ordered on patients who are suspected of having narcolepsy or other causes of hypersomnia (Idiopathic hypersomnia, Kleine-Levin Syndrome, shift work desynchronosis, and other causes of excessive daytime sleepiness).

The order for MSLT is usually given by the sleep specialist who assesses the referral form. Often the patient is phoned to get further information if hypersomnia is suspected from the referral.

Apnea as a cause of excessive daytime sleepiness is usually excluded prior to performing MLSTs and a overnight sleep test (PSG) is always performed prior to the daytime test to ensure accuaracy of the daytime napping pattern. A diagnosis of narcolepsy can have a profound effect on a patient's life.