Common symptoms of idiopathic hypersominia (IH) include:

• Chronic excessive daytime sleepiness (EDS): sleepiness during the day that makes it difficult to perform normal daily activities, including both work- and social-related activities.
• Sleeping 9 hours or more over 24-hour periods, yet not feeling refreshed upon waking from nighttime sleep or naps.
• Non-refreshing daytime napping.
• Sleep drunkeness after nighttime sleep and naps: difficulty waking up and feeling an uncontrollable desire to go back to sleep.
• "Brain fog" while awake: experiencing problems with memory, attention and concentration.
• Headaches.

Other symptoms reported by people with IH include:

• Short sleep latency: taking a shorter than normal time to fall asleep, often less than 8 minutes on the multiple sleep latency test (MSLT).
• Harder time regulating body temperature.
• Raynaud's disease.
• Excessive sweating.
• Episodes of feeling faint.
• Blood pressure drops right after standing up (orthostasis).
• Sleep paralysis.
• Sleep-related hallucinations.

Treatments for hypersomnia are generally aimed at excessive daytime sleepiness (EDS), rather than at sleep duration or sleep drunkenness (confusion upon waking up). Although there are multiple treatments approved by the Food and Drug Administration (FDA) for narcolepsy, there are no FDA-approved treatments idiopathic hypersomnia (IH). Therefore, treatment generally involves off-label use of medications approved for narcolepsy. Unfortunately, the use of these medications is inadequate to improve symptoms in many people with IH. These medication options may include:

• Wakefulness-promoting agents (modafinil and armodafinil)
• Traditional psychostimulants (amphetamines, methylphenidate, and their derivatives)

There are also several emerging therapies for cases that do not respond to the above types of medications. These include sodium oxybate, clarithromycin, and flumazenil.Non-medical approaches such as behavior modification are not generally effective for people with IH. Unlike in narcolepsy, where scheduled naps can help, daytime naps in people with IH are typically long and nonrestorative.

People with IH should avoid activities that may be dangerous, and should avoid driving or operating dangerous machinery unless sleepiness is well controlled by medication.

Following up with physicians at least annually (preferably more frequently) is recommended to assess for side effects of medication, sleep or mood disturbances, adequate control of symptoms, and any work-related or social issues.