Narcolepsy is typically diagnosed after a sleep study followed by a Multiple Sleep Latency Test. The sleep study is an overnight test conducted in a controlled environment (usually a clinic designed for these types of tests) and is used to set a baseline of what a 'typical' night's sleep is like. After the overnight sleep study, the MSLT is usually done the next day. The person is asked to stay awake (no unscheduled naps). Once every two hours or so, clinic staff come in the person's room and ask him or her to lay down and take a 20-minute nap. This is repeated anywhere from 4 - 6 times during the day. Measurements taken during the MSLT include: Did the person fall asleep during the scheduled nap? If yes, how long did it take the person to fall asleep? Did the person go into REM sleep during the nap? If yes, how long did it take?
People who tend to fall asleep fast (within 5 - 10 minutes of laying down) AND who enter REM sleep quickly (within 5 minutes of falling asleep) could be narcoleptic.
Doctors who are certified as sleep specialists and/or neurologists are essential for those who are diagnosed with narcolepsy.
Additionally, there is a genetic marker for narcolepsy, although this does not appear in all PWN, so is not a definitive test.