What are the Causes of Drowsiness?

A variety of things may cause drowsiness. These can range from mental states and lifestyle choices to serious medical conditions.

Lifestyle factors

Certain lifestyle factors may lead to increased drowsiness, such as working very long hours or switching to a night shift. In most cases, your drowsiness will subside as your body adapts to your new schedule.

Mental state

Drowsiness can also be a result of your mental, emotional, or psychological state.

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Depression can increase drowsiness, as can high levels of stress or anxiety. Boredom is another known cause of drowsiness. If you’re experiencing any mental conditions, you’re also likely to feel fatigued and apathetic.

Medical conditions

Some medical conditions can cause drowsiness. One of the most common of these is diabetes. Other conditions that may lead to drowsiness include those that cause chronic pain or affect your metabolism or mental states, such as hypothyroidism or hyponatremia. Hyponatremia is when the level of sodium in your blood is too low.

Other medical conditions that are known to cause drowsiness to include:


Many medications, especially antihistamines, tranquilizers, and sleeping pills, list drowsiness as a possible side effect. These medications have a label that warns against driving or operating heavy machinery while using these drugs.

Talk to your doctor if you experience prolonged drowsiness due to your medications. They may prescribe an alternative or adjust your current dosage.

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Sleeping disorder

Excessive drowsiness without a known cause can be a sign of a sleeping disorder. There’s a variety of sleeping disorders, and each has its own unique effects.

In obstructive sleep apnea, a blockage in your upper airways leads to snoring and pauses in your breathing throughout the night. This causes you to wake up frequently with a choking sound.

Other sleep disorders include

  •  narcolepsy
  •  restless leg syndrome (RLS)
  • delayed sleep phase disorder (DSPS).

Treatment of drowsiness depends on its cause.


Some drowsiness can be treated at home, especially if it’s due to lifestyle factors, such as working longer hours, or a mental state, such as stress.

In these cases, it may help to get plenty of rest and distract yourself. It’s also important to investigate what’s causing the problem, like stress or anxiety, and take steps to reduce the feeling.

Medical care

During your appointment, your doctor will try to identify the cause of your drowsiness by discussing the symptom with you. They may ask you about how well you sleep and whether you wake up frequently at night.

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Be prepared to answer questions about:

  • your sleeping habits
  • the amount of sleep you get
  • if you snore
  • how often you fall asleep during the day
  • how often you feel drowsy during the day

Your doctor may ask you to keep a diary of your sleeping habits for a few days, documenting how long you sleep at night and what you’re doing when you feel drowsy during the day.

They may also ask for specific details, such as if you actually fall asleep during the day and whether you wake up feeling refreshed.

If the doctor suspects that the cause is psychological, they may refer you to a counselor or therapist to help you find a solution.

Drowsiness, which’s a side effect of the medication, is often curable. Your doctor may swap the medication for a different type or change your dosage until the drowsiness subsides. Never change your dosage or stop prescription medication without first talking to your doctor.

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If no cause for your drowsiness is apparent, you may need to undergo some tests. Most are usually noninvasive and painless. Your doctor could request any of the following:

  • complete blood count (CBC)
  • electroencephalogram (EEG)
  • urine tests
  • CT scan of the head

If your doctor suspects that you may have obstructive sleep apnea, RLS, or another sleep disorder, they may schedule a sleep study test. For this test, you’ll spend the night in the hospital or a sleep center under the observation and care of a sleep specialist.

Your blood pressure, heart rate, heart rhythm, breathing, oxygenation, brain waves, and certain body movements will be monitored throughout the night for any signs of a sleep disorder.

When to seek emergency care

You should seek medical attention if you begin to feel drowsy after you:

  • start a new medication
  • take an overdose of medication
  • become exposed to the cold
  • sustain a head injury

A regular amount of sleep each night can often prevent drowsiness. Most adults require about eight hours of sleep to feel fully refreshed. Some people may need more, especially those with medical conditions or a particularly active lifestyle.

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Talk to your doctor as soon as possible if you experience any changes in your mood, signs of depression, or uncontrollable feelings of stress and anxiety.

What’s the risk for untreated drowsiness?

You may find that drowsiness goes away naturally as your body becomes used to a new schedule or as you become less stressed, depressed, or anxious.

Nevertheless, if the drowsiness is due to a medical problem or sleep disorder, it’s unlikely to get better on its own. In fact, the drowsiness is likely to worsen without proper treatment.

Some people manage to live with drowsiness. However, it may limit your ability to work, drive, and operate machinery safely.