The main symptom of Idiopathic Hypersomnia (IH) is feeling sleepy during the day. There are two forms of IH. In one, the person has a normal amount of sleep at night (i.e. up to 9 hours). In the other, they sleep for longer than usual at night (e.g. 12-14 hours). In both forms, people also sleep during the day, usually in long naps of 1-2 hours. However these naps are not refreshing and they wake up still feeling tired. Many people with IH also have a lot of trouble waking up in the morning. They may feel quite groggy as they surface from being asleep.

If you are always feeling sleepy and cannot explain why, you should talk to your doctor (see excessive daytime sleepiness). You probably don’t have IH if you feel tired or fatigued without the urge to sleep during the day. If you wake up refreshed after having a long sleep, then you probably don’t have IH.

If your GP feels you may have a sleep problem you will be referred to a sleep specialist. Many patients have IH for many years without knowing it. To determine if you have IH or another sleep disorder (e.g. narcolepsy), you may have a “Multiple Sleep Latency Test” in a clinic that does sleep studies.

For more information visit Sleep Health Foundation’s website.