Drowsiness refers to feeling unusually sleepy during the day. Being drowsy may lead to additional symptoms, such as forgetfulness or falling asleep at inappropriate times.

Various factors can cause drowsiness, ranging from mental states and lifestyle habits to underlying medical conditions.

Lifestyle factors

Certain lifestyle factors may lead to increased drowsiness, such as working very long hours or switching between time shifts at work. In most cases, your drowsiness will subside as your body adapts to the new schedule.

Mental state

Drowsiness can also occur due to your mental, emotional, or psychological state.

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

Medical conditions

Several medical conditions can lead to fatigue or drowsiness (a tendency to fall asleep). Diabetes is one of them — high or low blood sugar, dehydration, and sleep disruption in people with diabetes often contribute to fatigue.

Disorders that affect metabolism or electrolyte balance, such as hypothyroidism or hyponatremia, can also cause low energy and drowsiness. Infectious mononucleosis (mono) commonly causes extreme fatigue during the acute illness, and in a minority of people, it can trigger a persistent postviral fatigue syndrome or chronic fatigue syndrome (CFS).

However, drowsiness also frequently occurs due to sleep disorders, medication side effects, or mood disorders, so it’s important to look at the full picture.

Medications

Many medications, particularly 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 them.

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

Sleeping disorder

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

Treatment of drowsiness depends on its cause.

Self-treatment

Some drowsiness can be treated at home, especially if it’s the result of 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. It’s also important to investigate the source of the problem, such as stress or anxiety, and take steps to reduce these factors.

Medical care

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

Be prepared to answer questions about:

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 whether you actually fall asleep during the day and if you wake up feeling refreshed.

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

Drowsiness as a side effect of medication is often curable. Your doctor may swap the medication for a different type or change your dosage until the drowsiness subsides. However, never change your dosage or stop a prescription medication without first talking with a healthcare professional.

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:

If your healthcare team 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 a 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.

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

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

Getting enough quality sleep each night can often prevent drowsiness. Most adults require about 8 hours of sleep to feel fully refreshed. Some people may need more, especially those with medical conditions or a particularly active lifestyle.

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

You may find that drowsiness subsides as your body adjusts to a new schedule or as you become less stressed, depressed, or anxious.

However, if the drowsiness is due to a medical problem or sleep disorder, it’s unlikely to get better on its own. In fact, the issue 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.