Excessive Daytime Sleepiness: Common Causes and Treatments


Written by Janet Larson

Reviewed by Dr. Michael Breus

Our Editorial Process

Table of Contents

Excessive sleepiness is a common condition that can make people fall asleep during times they are expected to remain awake. As many as 1 in 4 people say they experience excessive sleepiness. Excessive sleepiness may be a sign of a sleep disorder or another condition that could improve with treatment.

Excessive sleepiness can make activities like driving risky, as well as impair school and work performance. Excessive sleepiness can affect quality of life. People with excessive sleepiness often have low energy for activities and worry about falling asleep at inappropriate or unexpected times.

Finding the cause of excessive sleepiness is the first step in getting relief.

Key Takeaways


  • Irregular sleep schedules and high stress levels can impact sleep quality and lead to excessive sleepiness even after a full night of sleep.
  • Chronic sleep deprivation, sleep disorders, mental health conditions, and medications can cause daytime sleepiness.
  • Excessive sleepiness can impair physical and cognitive functioning, increase the risk of accidents, and should be addressed with professional help.

What Is Excessive Daytime Sleepiness?

Excessive daytime sleepiness (EDS) is a condition in which people feel very sleepy in circumstances where they should be alert. People with EDS may find themselves falling asleep unintentionally. Daytime sleepiness is considered excessive when it is so difficult to stay awake during the day that it interferes with normal functioning.

Excessive sleepiness is often used interchangeably with the word fatigue. Although sleepiness and fatigue can overlap, they are different things.

Fatigue is a lack of physical or mental energy. People with fatigue feel a sense of weakness and grow tired very quickly during activities. In contrast, excessive sleepiness means drowsiness so strong that it gets in the way of daily activities, causing people to fall asleep at times they should remain awake.

Signs of Excessive Sleepiness

People with excessive daytime sleepiness tend to fall asleep in situations when others would normally be awake. They can nod off when they don’t want to, including at times that may be dangerous. People with EDS may doze off:

  • In a public place, such as a meeting or classroom
  • While talking to someone
  • While sitting
  • While reading
  • While watching television
  • In a car
  • While watching a theatrical performance

People with excessive daytime sleepiness may nap repeatedly during the day. Oftentimes their daytime naps are not refreshing.

What Causes Excessive Sleepiness?

People can become excessively sleepy during the day if they do not get enough hours of sleep at night.

They may also have EDS if their sleep is low-quality and unrefreshing, even if they sleep for a sufficient number of hours. Causes of insufficient or poor-quality sleep range from busy schedules to sleep disorders and serious medical issues.

Insufficient Sleep

A frequent cause of excessive daytime sleepiness is sleep loss. Although experts recommend that adults sleep 7 to 9 hours per night, many people fall short. In fact, about 1 in 3 adults in the U.S. say they regularly do not get enough sleep.

Work schedules, family life, and social obligations can all interfere with people’s ability to get enough sleep. When there’s a difference between the amount of sleep a person needs and the amount they get, “sleep debt” accumulates. This can lead to excessive sleepiness.

In addition to causing EDS, insufficient sleep can make accidents more common, depress the immune system, and contribute to obesity and cardiovascular problems.

Poor sleep quality can also make someone tired during the day. Sleep quality can be impacted by sleep fragmentation from waking during the night. Awakenings may be due to underlying sleep disorders and can occur without people being aware of them.

Sleep Apnea

Many people with sleep apnea experience EDS. Obstructive sleep apnea occurs when a person’s breathing pauses during sleep because of blocked airways. When this happens, people will partially awaken as they struggle to resume breathing. People are not usually aware of these partial awakenings.

The sleep fragmentation caused by sleep apnea, as well as by other sleep-related breathing problems, leads to a variety of symptoms that include excessive daytime sleepiness.

Sleep-Wake Disorders

We all have an internal sleep-wake cycle that helps us feel sleepy at night and awake during the day. This is one of our circadian rhythms. When circadian rhythms are disrupted, a sleep-wake disorder may develop, resulting in excessive daytime sleepiness. 

  • Jet lag disorder: Jet lag occurs when a traveler’s circadian rhythms don’t match up with a new time zone. Sleep, wake, and meal times will be out of alignment until their internal timing system can adjust.
  • Shift work disorder: Shift work disorder is a mismatch between circadian rhythms and the demands of working on an evening or night schedule. This mismatch can keep people awake when their schedule allows time for sleep and make them sleepy when they need to be alert.
  • Non-24-hour sleep-wake rhythm disorder: This disorder, common in people with blindness, develops when the circadian system is unable to stay in sync with the 24-hour day. 
  • Delayed sleep-wake phase disorder: Most common in teenagers, delayed sleep-wake phase disorder involves a delay in circadian rhythm and delayed sleep and wake times.
  • Advanced sleep-wake phase disorder: Believed to be more common in older people, this disorder develops when a person’s circadian rhythm causes them to wake up very early in the morning and become drowsy early in the evening.

Restless Legs Syndrome

People with restless legs syndrome feel a strong urge to move their legs. Although people may feel this urge while awake, it also frequently disturbs their sleep.

Restless legs syndrome and related disorders can make it harder to fall asleep, as well as to stay asleep. This can result in a person getting poorer quality sleep and less sleep overall.


Narcolepsy is a sleep disorder that usually arises from a lack of particular chemicals in the brain. Without these brain chemicals, people have trouble staying awake during the day. This leads to sleep attacks, during which a person briefly falls asleep while eating, driving, or having a conversation.

Excessive daytime sleepiness is the most prominent symptom of narcolepsy. Other symptoms can include hallucinations, sleep paralysis, and a loss of muscle control.

Mental Health

Certain mental health conditions may be linked to excessive daytime sleepiness. These include major depression, bipolar disorder, and seasonal affective disorder. These conditions can make people sleep more than usual and nap excessively. People with these conditions may also have trouble falling asleep or have frequent sleep disturbances.

Additionally, excessive sleepiness can be a side effect of mental health treatments, such as psychiatric drugs that cause drowsiness.

I always emphasize that a daytime nap is not a replacement for a full night of sleep. Yes, napping can relieve fatigue, but it can’t reverse the negative effects of chronic sleep loss nor provide the same restorative power as a full night’s rest.
Dr. Michael Breus

Health Conditions

A number of medical conditions cause daytime sleepiness. But if the condition responds successfully to treatment, the resulting sleepiness is likely to improve as well. Disorders that cause EDS include:

  • Underactive thyroid
  • Peptic ulcer
  • Gastroesophageal reflux disease
  • Chronic liver disease
  • Cancer
  • Parkinson’s disease
  • Alzheimer’s disease and other types of dementia
  • Brain inflammation, including viral encephalitis


Certain prescription medications, over-the-counter medicines, and recreational drugs may cause excessive daytime sleepiness. Some of these include:

  • Opioid pain medications
  • Antihistamines, often used to treat allergies
  • Antiseizure drugs
  • Drugs for heart disease and high blood pressure
  • Marijuana
  • Alcohol

If you are concerned that a prescribed medication may be causing daytime sleepiness, speak with your doctor before stopping or changing your dose.

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Diagnosing the Cause of Excessive Sleepiness

In some cases, the cause of EDS may be obvious. For instance, people who take certain medications, or who clearly do not get enough sleep, may not need further testing.

If doctors can’t readily determine the cause, they may order several different diagnostic tests. 

  • Health history: Health care providers often ask about a person’s medications, mood, and sleep habits, including any history of snoring or restless legs. They may ask when the sleepiness occurs and recommend keeping a sleep log.
  • Epworth Sleepiness Scale: This is a questionnaire that asks how likely a person is to doze off in certain situations. It can be helpful in distinguishing between people who have excessive sleepiness and those with low energy or fatigue.
  • Polysomnography: Also called a sleep study, polysomnography is performed in a sleep laboratory and involves taking physical measurements during sleep. This test provides information about a person’s sleep that can help diagnose sleep disorders, including sleep apnea and narcolepsy.
  • Home sleep apnea test (HSAT): When providers strongly suspect obstructive sleep apnea, they may order a home sleep test. This test is performed at home during sleep using a portable device.
  • Multiple sleep latency test (MSLT): An MSLT is performed in a sleep laboratory, usually immediately following polysomnography. An MSLT measures sleep latency, which is the amount of time it takes to fall asleep. If a person falls asleep in less than eight minutes, it usually indicates excessive daytime sleepiness.

Treating Excessive Daytime Sleepiness

The treatment of excessive daytime sleepiness depends on its underlying cause. For instance, if someone is sleepy because they are not getting enough sleep, their treatment might involve counseling to help them improve their sleep hygiene and create a sleep schedule.

However, if daytime sleepiness is due to a sleep disorder, treatment generally targets that disorder. Examples might include using a CPAP for sleep apnea or taking iron supplements or other medication for restless legs syndrome.

If a doctor determines that a medication is behind the sleepiness, they may recommend changing the medication or the time of day it is taken–for instance, at bedtime rather than during the day.

Sometimes the symptom of excessive sleepiness itself can be treated with medication. For example, people with narcolepsy might be treated with stimulants or drugs that promote wakefulness.

Risks of Untreated Excessive Sleepiness

Excessive daytime sleepiness can be dangerous. Sleepiness contributes to over 100,000 motor vehicle accidents every year, with 1 of every 6 fatal crashes caused by drowsy driving. It also makes operating other machinery hazardous and leads to overall poorer health.

When excessive daytime sleepiness is caused by sleep deprivation, the health consequences can be particularly severe. In addition to having a higher likelihood of accidents, people who don’t get enough sleep on a regular basis have a greater risk of:

  • Cardiovascular disease
  • Immune system suppression
  • Obesity, metabolic syndrome, and type 2 diabetes
  • Death from all causes

Fortunately, the causes of excessive sleepiness are treatable. And when the problem stems from insufficient sleep, improving sleep hygiene can be effective at increasing how much sleep you get.

Frequently Asked Questions About Excessive Sleepiness

Why am I sleepy even though I got eight hours of sleep last night?

There may be several reasons. First, your sleep quality may have been poor. Poor-quality sleep is marked by frequent awakenings, which you may not be aware of. These awakenings can be caused by a sleep disorder like obstructive sleep apnea or restless legs syndrome. It may also be due to a health condition or its treatment. Narcolepsy, mental health disorders, certain medications, and chronic health conditions can all make you feel sleepy during the day despite adequate nighttime sleep.

What causes excessive sleepiness in older people?

Older people have many of the same issues that cause excessive daytime sleepiness in younger people. But older adults are more susceptible to disorders known to impact sleep, such as dementia, sleep apnea, and acid reflux. In addition, sleep patterns alter as people age. Older people may sleep more lightly and wake more often. They tend to spend more time awake while they are in bed and get less total sleep. Moreover, older people are more likely to take prescription medications, including those that can cause EDS. Because of physical changes that affect how their bodies absorb and eliminate drugs, older people may also have more pronounced side effects from the medications they take.

How can I find out why I am always sleepy?

First, keep track of how much sleep you are getting. Adults need between 7 and 9 hours of sleep a night, and teenagers need 8 to 10. If you are getting less sleep than you need, your daytime sleepiness may simply be due to insufficient sleep. If so, you can try revising your sleep schedule and practicing good sleep hygiene to get more sleep. If you are getting the required amount of sleep but are still sleepy, you should discuss your sleepiness with your health care provider. Your doctor can review your medical history and may order tests to determine what is causing you to feel so drowsy.

What can I do to stop falling asleep during the day?

If you are dealing with excessive daytime sleepiness, it is critical to avoid driving and other activities that could put you or others in danger if you fall asleep. Successful treatments exist for many conditions that cause EDS, so make sure to speak with your doctor. The solution may be as simple as adjusting your sleep schedule and improving your sleep hygiene so you get enough sleep. Your health care provider may need to order tests to learn the cause of your EDS. If they detect a sleep disorder or other medical condition, they may recommend treatment for it.


About The Author

Janet Larson

Staff Writer, Sleep Health

Janet is a freelance writer and editor who lives in Fancy Gap, Virginia. She has a bachelor’s degree in literature from Bennington College and has worked for Fred Hutchinson Cancer Center. Janet particularly likes writing about sleep because it’s both mysterious and ordinary. She says it’s impossible for her to sleep without three pillows.

  • POSITION: Side Sleeper
  • TEMPERATURE: Cold Sleeper
  • CHRONOTYPE: Dolphin

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