If you find yourself forcing yourself to stay awake at work, unintentionally dozing off while reading, attending meetings, or traveling, this problem may be more than just general fatigue. "Drowsiness" refers to a tendency to fall asleep or difficulty maintaining alertness, while "fatigue" is feeling exhausted or lacking energy, but not necessarily needing to sleep. Both can occur simultaneously, but they shouldn't always be used interchangeably.¹^,3

Excessive daytime sleepiness is a symptom, not a disease. Causes can range from common issues like insufficient sleep, irregular sleep schedules, shift work, alcohol consumption, or certain medications, to sleep disorders and other health problems. Assessment therefore requires considering 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 had the chance to sit still right now, would I likely fall asleep?"” If the answer is yes, or you've accidentally fallen asleep, that's closer to drowsiness than fatigue.³

What is the difference between feeling sleepy and feeling tired?

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.

It's also worth noting that you may have fallen asleep while reading, watching television, in a meeting, traveling in a car, or driving for extended periods.³^,8

Physical and mental health conditions, stress, and poor sleep can all contribute to drowsiness and fatigue. If these symptoms persist or significantly impact your life, consult a doctor to determine the cause.³

What should be emphasized is not just "how many times" you feel drowsy, but whether the symptoms make it difficult to work, study, travel, converse, or carry out daily activities. Because drowsiness that affects safety and quality of life should be evaluated to determine its 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 consistently get at least seven hours of sleep per night. However, individual needs vary, and sleep health depends on timing, consistency, quality, and the presence of sleep disorders, not just the number of hours slept.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. If you work nights or shifts, your work hours may not align with your body's natural sleep and wake cycles, potentially leading to shorter sleep periods or reduced sleep quality. Research among the US workforce has 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 discuss with your doctor or pharmacist. Alcohol can increase drowsiness and impair your ability to drive.³^,8

Caffeine may provide a temporary boost of alertness, but it cannot compensate for severe sleep deprivation or make driving safe when drowsy.⁸

Sleep is disturbed, even though I sleep for the full number of hours.

Spending a lot of time in bed doesn't always mean getting uninterrupted or restful sleep. Difficulty falling asleep, frequent awakenings, or sleep-related breathing disorders can lead to feeling unrested and drowsy upon waking up.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 helps evaluate levels of drowsiness, and the STOP-Bang model can screen for initial risk of OSA, but scores from the assessments cannot be used 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 separate diagnosis from other conditions. Excessive sleepiness alone is insufficient to confirm a specific disorder, and each condition is treated differently. A clear diagnosis is necessary before treatment; self-medication with stimulants is not recommended.⁹^,10

If you experience sudden episodes of intense drowsiness or involuntary sleepiness, or temporary muscle weakness when experiencing emotions such as laughter, excitement, or anger, you should describe these symptoms in detail to your doctor. These symptoms are for evaluation purposes only and are not proof 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 numerous and the symptoms may overlap. Therefore, self-checking a list of illnesses will not help to confirm which condition it is.³

Doctors will choose to take a medical history, perform a physical examination, or order tests based on each individual's information. It is not necessary to test everything or perform a sleep test on everyone.³

What can you check before seeing a doctor?

Try keeping a continuous journal for about 2 weeks, recording as much information as you can, as follows: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 activities at that time.
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

During data collection, ensure you get enough sleep and try to go to bed and wake up at a consistent time if possible. However, avoid using sleep schedules as an excuse to postpone doctor's appointments if symptoms occur frequently, affect your daily life, or pose a risk of accidents.¹^,2

Do not stop your medication on your own. Do not buy stimulants to wake you up. And do not start CPAP based on the assumption that you have OSA. The 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 may indicate OSA, such as loud snoring, being seen to stop breathing, gasping or choking, and waking up feeling unrested.⁵^,7
Experience episodes of intense drowsiness or sudden, involuntary sleepiness, or temporary muscle weakness when experiencing emotions such as laughter, excitement, or anger. 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 start with a sleep test. A doctor may begin with a history of sleep, medication, physical and mental health, and then select additional tests based on the suspected cause.³

What should you do if you're driving or working in a risky job while drowsy?

If you're struggling to stay awake, losing focus, your car starts drifting out of its lane, or you step on a roadside warning strip... Don't drive any further. Stop at a safe location 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 medication labels and consult a specialist if the medication contains warnings about drowsiness or driving.

Coffee or energy drinks may provide a short-term boost and may make you feel more awake than you actually are, especially when you're severely sleep-deprived. Therefore, this should not be used as an excuse to continue driving.⁸

Drowsiness and fatigue reduce alertness and increase the risk of workplace injury. If you must work with machinery, at heights, on electricity, or perform other tasks where mistakes could lead to injury, do not continue. Inform your supervisor or responsible person 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?

The doctor may ask when you started feeling drowsy, at what time of day, whether you fell asleep unintentionally, how many hours you sleep at night, whether you wake up frequently, whether you work shifts, whether anyone has noticed your symptoms while you sleep, and whether you are using 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.
This screening questionnaire is for initial assessment, not confirmation of 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; questionnaires or predictive algorithms should not be used alone.⁶

FAQ

Why am I still sleepy even after sleeping for 7-8 hours?

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" helps to differentiate the problems better than using a general term for tiredness.¹^,3

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

It's not conclusive that OSA is just one of many causes. Several symptoms should be considered together, such as loud snoring, sleep apnea, startled awakenings, frequent 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 organize initial information, but the score is not a diagnosis. The UK's National Institute for Health and Care Excellence (NICE) states that Epworth scores should not be used alone to determine referral, and the AASM recommends against using clinical tools or OSA diagnostic questionnaires without a 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 check the name of the medication, dosage, timing of use, and any side effects with your doctor or pharmacist, 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 the symptoms affect your life or safety, if you remain drowsy even when you have the opportunity to get enough sleep, or if you have any accompanying symptoms that suggest a sleep disorder. Early detection doesn't mean everyone needs a sleep test, but it can help select the most appropriate assessment to address 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 have many 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

Start by differentiating between "drowsiness that suggests a likelihood of falling asleep" and "fatigue but not necessarily sleepy." Note down your sleep patterns and associated symptoms. Review your medication with a specialist and consider the impact on your life. If you feel drowsy while driving, pull over in a safe place. If you feel drowsy while performing risky work, 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, questionnaire scores, or answers to 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?