The main symptom of 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.