If you find yourself forcing yourself to stay awake at work, or unintentionally dozing off while reading, attending a meeting, or traveling, this might be more than just ordinary fatigue. "Drowsiness" means a tendency to fall asleep or difficulty staying awake, while "fatigue" is feeling exhausted or lacking energy, but not necessarily needing to sleep. These two symptoms can occur together, but they shouldn't always be considered the same thing.^[1,3]

Excessive daytime sleepiness is a symptom, not a disease. Causes range from common issues like insufficient sleep, irregular sleep schedules, shift work, alcohol consumption, or certain medications, to sleep disorders and other health problems. Therefore, assessment requires considering multiple factors, including sleep patterns, medications used, co-occurring symptoms, and the impact on quality of life. A single symptom should not be used to conclude the cause.^[1,3]

How is excessive drowsiness different from fatigue?

Ask yourself: “"If I just sat still right now, would I fall asleep?"” If the answer is yes, or if you've ever unintentionally fallen asleep, that feeling is closer to "drowsiness" than "fatigue."“^[3]

Comparing drowsiness with fatigue.

sleepy

It is likely that you will fall asleep or have difficulty waking up.

Heavy eyelids, falling asleep, or losing concentration because you're about to fall asleep.

tired

Feeling tired or drained, but not necessarily needing to sleep.

Easily tired, lack of interest in activities, or feeling weak.

Another thing to consider is whether you've ever fallen asleep while reading, watching television, in a meeting, riding in a car, or driving for long periods of time.^[3,8]

Physical and mental health issues, stress, and poor sleep can all cause drowsiness and fatigue. If these symptoms persist or affect your daily life, you should consult a doctor to determine the cause.^[3]

The important thing is not just "how many times you feel drowsy," but whether that drowsiness makes work, studying, traveling, talking, or daily life difficult. Because if drowsiness affects your safety and quality of life, you should consult a doctor to evaluate and determine the cause.^[1]

What can cause daytime sleepiness?

Insufficient sleep or irregular sleep patterns.

The first thing to reconsider is whether you're actually getting enough sleep. The American Academy of Sleep Medicine (AASM) and the Sleep Research Society (SRS) recommend that healthy adults get at least 7 hours of sleep per night regularly, but individual needs vary. Furthermore, good sleep isn't measured solely by the number of hours; it also depends on the timing of sleep, consistency, quality, and the presence of any co-existing sleep disorders.^[2]

Going to bed late, waking up early, getting insufficient sleep for several days, or frequently changing sleep schedules can all contribute to daytime drowsiness. For those who work night shifts or rotating shifts, their work hours may not align with the body's natural sleep and wake cycles, leading to shorter sleep periods or reduced sleep quality. Research on a group of workers in the United States found a correlation between night shifts and increased sleep problems and drowsiness, but this doesn't mean all shift workers experience the same symptoms.^[4]

Drugs, alcohol, other substances, and caffeine.

Many types of medication can cause drowsiness, such as sleeping pills, some antihistamines, some pain relievers, anti-anxiety medications, and some psychiatric drugs. However, side effects vary depending on the specific medication, dosage, timing of use, and the individual.^[3]

If you suspect that the medication is causing you drowsiness. Do not stop taking your medication, reduce the dosage, or change the time you take it on your own. You should bring a list of prescription medications, over-the-counter drugs, and supplements to your doctor or pharmacist. Alcohol can also increase drowsiness and impair driving ability.^[3,8]

Caffeine may provide a temporary boost of alertness, but it doesn't compensate for severe sleep deprivation and doesn't make driving while drowsy safe.^[8]

I got my full night's sleep, but my sleep was disturbed.

Spending a lot of time in bed doesn't necessarily mean uninterrupted sleep or complete rest. If you have difficulty falling asleep, wake up frequently, or experience breathing difficulties during sleep, you may wake up feeling unrested and drowsy during the day.^[3,7]

Obstructive sleep apnea, or OSA, can also be a cause of sleep disturbance. Several symptoms should be observed together, such as loud snoring, being noticed stopping breathing, gasping or choking during sleep, frequent awakenings, feeling unrested after sleep, and excessive daytime sleepiness. These symptoms are signs that warrant further medical evaluation, but they don't necessarily confirm OSA.^[5,7]

The Epworth assessment measures levels of drowsiness, and the STOP-Bang model screens for initial risk of OSA, but scores from these assessments are not sufficient to diagnose OSA. Diagnosis requires a comprehensive sleep assessment combined with an appropriate sleep study.^[5,6]

Diseases that directly cause abnormal drowsiness.

Narcolepsy and idiopathic hypersomnia are sleep disorders that require differential diagnosis. Excessive sleepiness alone is insufficient to confirm a specific condition, and because each condition requires different treatments, a clear diagnosis is crucial before starting treatment. Self-medicating with stimulants should be avoided.^[9,10]

If you experience sudden, intense drowsiness that is uncontrollable, involuntarily falling asleep, or temporary muscle weakness when experiencing strong emotions such as laughter, excitement, anger, or fear, you should describe these symptoms in detail to your doctor. These symptoms are for evaluation purposes only and are not evidence of narcolepsy.^[10]

Other health factors

Drowsiness or fatigue can be related to physical health problems, mental health issues, or chronic pain, but the causes are diverse and the symptoms may overlap. Therefore, simply comparing symptoms to a list of diseases alone cannot confirm which condition it is.^[3]

The doctor will choose the most suitable assessment method, whether it's taking a medical history, performing a physical examination, or ordering tests, based on each individual's information. It's not necessary to test everything, and not everyone needs a sleep study.^[3]

What can you check before seeing a doctor?

Try keeping a sleep journal for about two consecutive weeks, recording as much information as you can about the following.^[11]

Bedtime, expected sleep time, wake-up time, and periods of nighttime awakenings.
Napping or accidentally falling asleep during the day, along with the time and what you were doing at that moment.
Are you feeling refreshed after waking up, or are you still very sleepy?
Symptoms such as snoring, gasping for breath, choking, or apnea that are noticed by those close to the patient.^[5,7]
Medications, supplements, alcohol, and the timing of caffeine consumption.
Work shift schedule, days with long drives, or hazardous work.^[4,8,12]
It can affect concentration, memory, mood, work, studies, or relationships.^[1]

While keeping a journal, if possible, allocate time for sufficient sleep and try to maintain a consistent bedtime and wake-up time. However, if symptoms occur frequently, affect daily life, or pose a risk of accidents, do not delay adjusting your sleep schedule and postpone your doctor's appointment.^[1,2]

Do not stop your medication on your own. Do not buy stimulants to wake you up. And do not start using a CPAP machine simply because you suspect you have OSA. Appropriate care and treatment must be chosen based on the cause diagnosed by your doctor.^[3,6,9]

When should you see a doctor?

You should schedule an appointment with a doctor for an evaluation if any of the following conditions apply.^[1,3]

Do you frequently fall asleep or nearly fall asleep during the day?
Drowsiness can affect work, studies, travel, relationships, or daily routines.
I'm still very sleepy even though I've made sure to get enough and consistent sleep.
Several symptoms suggest OSA (Obstructive Sleep Apnea), such as loud snoring, being observed to stop breathing, gasping or choking, and waking up feeling unrested.^[5,7]
There may be periods of intense, rapid, and irresistible drowsiness, or involuntary sleepiness, or temporary muscle weakness during intense emotions such as laughter, excitement, anger, or fear. These symptoms are for assessment purposes only and are not evidence of narcolepsy.^[10]
I suspect that the medication or substance I'm using is causing me to feel drowsy.

An evaluation doesn't always have to begin with a sleep study. A doctor may start with a history of sleep, medications, physical and mental health, and then select additional tests based on the suspected cause.^[3]

What should you do if you feel drowsy while driving or performing risky work?

If you're struggling to stay awake, your concentration wavers, your car starts drifting out of its lane, or your wheels run over the roadside warning strips. Don't drive any further. Find a safe place and park the car first.^[8]

Change drivers or use an alternative mode of transportation.
If you are still sleepy or not focused... You should not go back to driving or doing risky work.^[8,12]
Check the medication label for warnings about drowsiness or driving. If so, consult your doctor or pharmacist and do not stop or adjust your medication on your own.

Coffee or energy drinks may only provide a short-term boost and may make you feel more alert than you actually are, especially when you're severely sleep-deprived. Therefore, you shouldn't assume that drinking them will allow you to continue driving.^[8]

Drowsiness and fatigue reduce alertness and increase the risk of work-related injury. If you have to work with machinery, at heights, on electrical systems, or any other task where a mistake could lead to injury, do not continue. Inform your supervisor or the person in charge so they can manage the risk according to workplace protocols.^[12]

A well-dressed man is yawning while seated at a table with other senior figures in a conference room with no readable text.

What might a doctor assess?

Your doctor may ask when you started feeling drowsy, what time of day you usually feel drowsy, if you've ever unintentionally fallen asleep, how many hours you sleep at night, how often you wake up, whether you work shifts, if anyone has ever noticed you feeling drowsy while you sleep, and if you use any medications, alcohol, or other substances.^[3]

Factors that may be used in the evaluation include:^[3,6]

Sleep history and sleep records.
List of medications, supplements, alcohol, and other substances.
Impact on quality of life and safety.
The screening questionnaire, used for initial assessment, does not confirm the disease.
Certain blood tests are performed when a physical cause is suspected.
A sleep study should be conducted when a patient's history indicates a sleep disorder that warrants examination.

For OSA, the American Academy of Sleep Medicine (AASM) guidelines state that diagnosis should be made in conjunction with a complete sleep assessment and the use of appropriate sleep studies. Clinical tools, questionnaires, or predictive risk models alone should not be used to diagnose OSA without such studies.^[6]

FAQ

I've slept enough, why am I still sleepy?

The number of hours of sleep is only one factor. You may wake up frequently, have irregular sleep schedules, poor sleep quality, are taking medications that cause drowsiness, work shifts, or have underlying health problems or sleep disorders. If you experience persistent drowsiness even when you have the opportunity to get enough sleep, you should consult a doctor to find the cause.^[2,3]

How is feeling sleepy all the time different from feeling tired?

Drowsiness refers to a tendency to fall asleep or difficulty staying awake, while fatigue is feeling exhausted or lacking energy without necessarily needing to sleep. Both can occur simultaneously. Telling your doctor "when you accidentally fall asleep" and "when you feel exhausted but can't sleep" will help differentiate the problems better than simply saying "I'm tired."“^[1,3]

Does feeling sleepy during the day mean I have sleep apnea?

It's not conclusive yet. OSA is just one of many causes of excessive sleepiness. Several symptoms should be considered together, such as loud snoring, sleep apnea, sudden awakenings, restless sleep, and excessive drowsiness. Confirmation of the condition requires evaluation and a sleep study.^[5,6]

Can the Epworth or STOP-Bang assessments diagnose diseases?

No, the assessment helps to screen and gather initial information, but the score is not a diagnosis. The National Institute for Health and Care Excellence (NICE) in the UK states that the Epworth score should not be used alone to decide whether to refer a patient, and the AASM recommends that clinical tools, questionnaires, or risk assessments alone should not be used to diagnose OSA without a proper sleep study.^[5,6]

Should I stop taking the medication if I'm drowsy?

You should not stop taking medication on your own. You should consult a doctor or pharmacist about the name of the medication, the dosage, the time of use, and any symptoms you experience, as stopping or changing the dosage yourself can be dangerous.^[3]

How sleepy should you be before you should see a doctor?

You should see a doctor if you frequently fall asleep unintentionally, if it affects your life or safety, if you still feel sleepy even after getting enough sleep, or if you have other symptoms that suggest a sleep disorder. Seeing a doctor early doesn't mean everyone needs a sleep study, but it can help you choose the most appropriate assessment to determine the cause.^[1,3]

If you feel drowsy while driving, can coffee help you keep driving?

Don't assume that drinking coffee will allow you to continue driving safely. Caffeine only provides temporary alertness, and with severe sleep deprivation, you may still fall asleep without realizing it. Pull over to a safe place, change drivers or use an alternative mode of transportation, and get enough rest.^[8]

summarize

Excessive daytime sleepiness can stem from a variety of causes, ranging from insufficient sleep, irregular sleep schedules, shift work, certain medications, alcohol consumption, and sleep disturbances, to sleep disorders and other health problems.^[2,3,4]

First, try to differentiate between "drowsiness that makes you likely to fall asleep" and "fatigue but not to the point of falling asleep." Note down your sleep patterns and associated symptoms. Review any medications you are taking with your doctor or pharmacist, and consider the impact on your life. If you feel drowsy while driving, pull over to a safe place. If you feel drowsy while performing a risky task, inform your supervisor and follow safety protocols. Do not force yourself or rely on caffeine to continue.^[3,8,12]

Doctors need to find the cause before they can choose the appropriate treatment. Symptoms alone, scores from questionnaires, or answers from articles cannot be used to confirm a disease or replace a doctor's diagnosis.^[1,3,6]

What causes excessive daytime sleepiness, and what can I do about it?