Lethargy causes you to feel sleepy or fatigued and sluggish. This sluggishness may be physical or mental. People with these symptoms are described as lethargic.

Lethargy can be related to an underlying physical or mental condition.

Lethargy can cause some or all of the following symptoms:

People with lethargy may act as if they’re in a daze. They may move more slowly than usual.

Many kinds of acute illnesses can make you feel lethargic. This includes the flu or a stomach virus. Other physical or medical conditions can also cause lethargy, such as:

Lethargy can also be the result of mental health conditions. These include:

Lethargy can also be a side effect of taking certain medications, such as narcotics.

Symptoms of lethargy may require emergency medical attention, especially if they come on suddenly. Seek emergency medical attention if you experience lethargy along with the following symptoms:

Any noticeable, marked changes in behavior accompanied by lethargy are often cause for concern. Seek immediate medical attention if you experience thoughts of harming yourself along with lethargy.

You may also want to make an appointment at your doctor’s office if you experience any of these symptoms alongside lethargy:

Lethargy in babies or young children

Babies or young children can also experience lethargy. Symptoms in babies that may need immediate medical attention include:

Your doctor will usually take a full medical history to discuss any of your previous medical conditions.

They may also perform a physical exam that can include:

Diagnostic testing typically depends on what your doctor suspects may be an underlying cause. For example, if your doctor thinks you may have a thyroid disorder, they may order blood tests to determine if your thyroid hormones are high or low.

Your doctor may order imaging studies, such as a CT or MRI scan, if they suspect the cause is brain-related, such as a head injury, stroke, or meningitis.

Treatment for lethargy depends upon its underlying cause.

For example, they may prescribe antidepressants if your lethargy is caused by depression or another mental health disorder.

You can practice healthy habits at home to reduce the fatigue related to lethargy. Examples include:

Make an appointment with your healthcare provider if these healthy habits don’t help your symptoms.