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We all have the occasional sleepy day — maybe after a bad night’s sleep or a late night out with friends. But when overwhelming fatigue and sleepiness happen every day — even after a full night’s rest — it may point to a sleep disorder.

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Could you be dealing with hypersomnia or narcolepsy? Both conditions cause persistent daytime sleepiness. But they affect your sleep-wake cycle in different ways, says sleep medicine specialist Nancy Foldvary-Schaefer, DO.

Hypersomnia vs. narcolepsy

“Hypersomnia” is an umbrella term for any condition that makes you feel extremely sleepy during the day (excessive daytime sleepiness) or have an excessive need to sleep. But when people talk about hypersomnia, they’re often referring to idiopathic hypersomnia (IH).

Both narcolepsy and IH are specific types of hypersomnia. They’re neurological sleep disorders that make it hard to stay awake during the day, which can interfere with everyday life. But they’re not the same condition.

The key differences between them come down to symptoms, Dr. Foldvary-Schaefer explains.

Idiopathic hypersomnia

Idiopathic hypersomnia is a condition that causes excessive sleepiness during the day, even when you’ve gotten plenty of sleep at night. “Idiopathic” means there’s no obvious cause for the condition.

Symptoms

If you have idiopathic hypersomnia, you may:

Sleep unusually long hours: “We generally think of people with IH as being deeper, longer sleepers than people with narcolepsy,” Dr. Foldvary-Schaefer says. “Some people with IH can sleep 10 to 16 or more hours within a 24-hour period.”
Experience sleep inertia: This is when your body has trouble transitioning from sleeping to waking up. You may feel disoriented, groggy and “sleep drunk.”
Find naps unrefreshing: Some people with IH feel that they have to take long and frequent naps. “Many choose not to nap, though, because it makes them feel even groggier,” Dr. Foldvary-Schaefer says.
Struggle to stay awake during the day: IH often brings low energy and fatigue, which can make daytime activities difficult or even impossible. “You may not have the energy to socialize or do much more than the core requirements for the day,” she says.
Have brain fog or memory and attention problems: Most people with IH report some degree of cognitive impairment, which may improve as the day goes on. Many experience irritability, depressed mood or anxiety, too, Dr. Foldvary-Schaefer notes.

These symptoms can make it hard to accomplish daily tasks, and they can start to affect your work, school performance, relationships and more.

“Most people with idiopathic hypersomnia have difficulty with day-to-day functioning and can become isolated,” Dr. Foldvary-Schaefer says. “They may be viewed by others as lazy, and they end up changing their lifestyles to fit their sleep disorder.”

Causes

When you have idiopathic hypersomnia, it means healthcare providers can’t identify a clear underlying cause for the condition.

“There are diagnostic tests that can confirm IH,” Dr. Foldvary-Schaefer says. “But we don’t yet understand the underlying biology of this condition.”

But again, don’t confuse IH for hypersomnia in general. IH is just one type of hypersomnia, and other types have clearer causes. Those types are called “secondary hypersomnia” — meaning excessive daytime sleepiness is a direct result of some other medical or psychiatric disorder, or some type of medication or substance.

Treatment

Treatment for idiopathic hypersomnia is focused on improving daytime alertness and managing symptoms. That may include:

Medication: “Stimulants and wake-promoting medications have historically been the go-to medications to promote wakefulness,” Dr. Foldvary-Schaefer explains. Lower-sodium oxybate is the only U.S. Food and Drug Administration (FDA)-approved treatment for IH. It’s been shown to alleviate many of the symptoms of IH, including sleep inertia and the need for naps.
Lifestyle changes: Stricter sleep hygiene practices, like maintaining a consistent sleep schedule, can help regulate your circadian rhythm.
Treating other medical conditions: If other health conditions could be making your sleepiness worse, your healthcare provider will want to focus on managing them. They’ll also look into adjusting any other medications you take that could make your sleepiness worse.
Education and support: Dr. Foldvary-Schaefer recommends looking into organizations like the Hypersomnia Foundation, which provides a variety of resources to help people with IH and their caregivers.

“People with IH often say that they’ve struggled with sleepiness for years, if not decades, and they feel they've been written off as being lazy or unmotivated,” Dr. Foldvary-Schaefer reports. “It can be a difficult diagnosis to pin down.”

But she adds that new treatments are being studied. Current clinical trials are looking into medications that target different wake-promoting pathways in the brain.

Narcolepsy

Narcolepsy is characterized by excessive daytime sleepiness, even after you’ve had the opportunity to get enough sleep at night. People with narcolepsy experience sudden “sleep attacks,” meaning they may fall asleep unexpectedly during the day — even during activities like talking, eating or working.

This condition is divided into two types:

Narcolepsy type 1 (NT1) is characterized by a type of sudden muscle weakness known as cataplexy.
Narcolepsy type 2 (NT2) does not involve cataplexy.

Symptoms

In addition to excessive daytime sleepiness, other narcolepsy symptoms may include:

Cataplexy: “This sudden muscle weakness, which only happens with narcolepsy type 1, is triggered by strong emotions — usually positive, like laughing or joking,” Dr. Foldvary-Schaefer says. You may feel your head droop or your knees buckle.
Hallucinations: You may have vivid, dream-like and sometimes-scary hallucinations when you fall asleep or wake up. You might, for example, feel like you’re levitating, sense someone is touching you or hear a sound that isn’t there.
Sleep paralysis: This is the feeling that you can’t move or speak as you fall asleep or as you’re waking up. It often happens at the same time as hallucinations.
Daytime naps: People with narcolepsy generally feel refreshed after sleep — at least temporarily, anyway.
Sleep disruptions: “People often think that narcoleptics must be really sound sleepers at night,” Dr. Foldvary-Schaefer says. “But people with narcolepsy often wake up a lot, often with vivid dream recollection.”

Causes

Narcolepsy is linked to problems in the areas of the brain that regulate sleep.

“Narcolepsy with cataplexy is caused by an autoimmune-mediated loss of neurons in the brain that produce hypocretin,” Dr. Foldvary-Schaefer explains. “Hypocretin is a neurotransmitter that helps regulate wakefulness and REM sleep.”

But experts don’t yet fully understand what causes narcolepsy type 2.

“Narcolepsy type 2 has features that overlap with narcolepsy type 1 but also with IH,” she continues. “We do not yet understand the neurobiology of it.”

Sometimes, other medical conditions, like a stroke, multiple sclerosis or head trauma, cause narcolepsy. This is known as secondary narcolepsy.

Treatment

“There’s no cure for narcolepsy,” Dr. Foldvary-Schaefer says. “But many people with narcolepsy successfully manage their symptoms with the right treatment plan.”

Treatment strategies often include:

Medication: Various types of medications (including stimulants, oxybates and histamine-affecting drugs) help promote wakefulness. “They can treat the symptoms but don’t get to the underlying deficiency that causes narcolepsy,” Dr. Foldvary-Schaefer points out.
Lifestyle changes: Your healthcare provider may recommend habit changes that can help you stay awake, like getting enough sleep, maintaining a regular sleep-wake schedule and avoiding alcohol.
Naps: Short, scheduled naps (20 to 30 minutes) may help ward off sleep attacks. In some cases, your provider may recommend that you seek accommodations at work or school so that you can take daytime naps.
Education and support: “Organizations like Narcolepsy Network and Project Sleep offer top-notch support for people with narcolepsy and their caregivers,” Dr. Foldvary-Schaefer advocates.

Importantly, she says that new narcolepsy treatments are on the horizon.

“There’s a lot of active investigation in this area,” Dr. Foldvary-Schaefer shares. “Right now, there are clinical trials studying drugs that boost a neurotransmitter called orexin in the brain. These trials show tremendous promise for treating the source of the problem in people with narcolepsy type 1.”

When to seek treatment

It’s one thing to feel tired some days. But it’s another thing to feel persistently, overwhelmingly sleepy every day.

Talk to a healthcare provider if you:

Feel excessively sleepy during the day despite getting enough sleep or require excessive sleep
Struggle to stay awake (or frequently fall asleep) during normal daily activities
Have an especially hard time waking up or feeling alert in the morning
Experience sudden muscle weakness, sleep paralysis or hallucinations related to sleep
Notice that your sleepiness is interfering with work, school or your own safety

Your healthcare provider may recommend that you have a sleep study to help figure out what’s causing your symptoms.

“Identifying the right condition is an important step toward finding treatment that can help you stay alert and improve your quality of life,” Dr. Foldvary-Schaefer says. “Both of these conditions are manageable. We can help.”