Lethargy, or fatigue, describes a state in which you are exhausted and have little to no energy. It is more profound and long-lasting than simply being tired or sleepy. Lethargy can be a symptom of certain diseases and health conditions or it can be a normal response to not getting enough sleep, stress, or eating poorly.

When lethargy develops as a response to various life situations, it often resolves with rest, increased sleep, good nutrition, and being active. However, in the case of illness, lethargy can linger for days, weeks, or even months.

This article discusses the symptoms and potential causes of lethargy. It also covers treatment options and information on when to contact your healthcare provider.

Symptoms of lethargy
Verywell / JR Bee 

Symptoms of Lethargy

Lethargy has been described as unrelenting exhaustion that includes chronic fatigue, lack of energy, and sluggishness. People who are lethargic may also experience:

  • Depression
  • Apathy (lack of interest in or enthusiasm for things)
  • Lack of motivation
  • Feeling less alert
  • Cognitive difficulties (forgetfulness and trouble concentrating)
  • Severe drowsiness

Other symptoms that may accompany lethargy include:

  • Aches and pains that won’t go away despite treatment
  • Sleep problems
  • Sensitivity to hot and cold temperatures
  • Eye inflammation
  • Chronic fatigue lasting more than two weeks
  • Swollen neck glands
  • Unexplained weight changes
  • Feeling sad, empty, or irritable

People who are lethargic may act as if they are in a daze. They may not move as quickly as they usually do and may be aware that they are in poor health.

Causes of Lethargy

Lethargy has a number of possible causes. It can be the body’s response to not getting enough sleep, overexertion, stress, lack of activity, or improper nutrition. It can also be a side effect of medication or the body’s response to alcohol. Consumption of alcohol while on medication can also cause a person to feel lethargic.

Lethargy is a symptom of many acute (abrupt onset) conditions, including the flu, stomach viruses, fever, dehydration, and nutritional deficiencies. Other serious medical conditions that cause lethargy include, but are not limited to:

Lethargy can also be a symptom of mental health disorders, including major depression and postpartum depression.

How to Treat Lethargy

If lethargy is caused by emotional or physical stress or exhaustion, it may not require medical treatment. It is often resolved by getting enough sleep, maintaining a healthy diet, and managing stress.

When lethargy is determined to be caused by an underlying cause, treatment is aimed at the cause. Here are possible treatments for lethargy, listed by the cause:

  • Dehydration: Treatment includes intravenous fluids and/or electrolyte consumption.
  • Hypothyroidism: Treatment may include thyroid replacement hormone, such as levothyroxine
  • Autoimmune diseases: Treatment may include relieving inflammation with disease-modifying antir-rheumatic drugs (DMARDs), nonsteroidal anti-inflammatory drugs (NSAIDs), and corticosteroids.
  • Depression: This can be treated by managing depressive symptoms with psychotherapy and/or antidepressant medications, such as Zoloft (sertraline) and Lexapro (escitalopram).
  • Cancer-associated lethargy: Healthcare providers may prescribe stimulant medications, such as Provigil (modafinil) for short periods to boost energy and increase wakefulness.

Are There Tests to Diagnose Lethargy?

The first step in determining the cause of lethargy is to see a practitioner. Your healthcare provider will take a medical history, ask you about your symptoms, and perform a physical exam. They may also do tests, including:

  • Blood tests to check for anemia, diabetes, inflammatory diseases, and possible infection
  • Kidney function tests
  • Liver function tests
  • Thyroid function tests
  • Urinalysis

Your healthcare provider may also recommend seeing a specialist if the cause of lethargy and other symptoms cannot be established. 

When to See a Healthcare Provider

Lethargy is rarely a medical emergency. However, it can become one if it is accompanied by other serious symptoms. It is important to seek immediate medical attention or call 911 for the following, which may be signs of a medical emergency:

  • Abdominal pain
  • Altered consciousness
  • Blurred vision
  • Chest pain
  • Confusion
  • Facial paralysis
  • High fever
  • Inability to move arms and legs
  • Nausea and vomiting
  • Rapid heart rate
  • Severe dizziness
  • Severe headache
  • Severe pain
  • Shortness of breath
  • Significant changes in behavior (including thoughts of self-harm)
  • Slurred speech
  • Sudden and severe swelling
  • Sudden energy loss

Lethargy in Babies and Children

Lethargy can also affect children and babies. Symptoms of lethargy that need immediate medical attention in young children and babies include:

  • Difficulty with waking or appearing to be in a daze, especially when accompanied by fevers higher than 102 degrees F
  • Weakness
  • Dehydration (including reduced tears, dry mouth, and decreased urine output)
  • Rashes
  • Vomiting


Lethargy involves more than being tired, sleepy, or drowsy. It is a state of being exhausted, with little to no energy, and it tends to linger. In some cases, lethargy may be due to certain life situations and lifestyle habits, but it can also be a symptom of certain diseases and health conditions. Treatment depends on the underlying cause.

A Word From Verywell

It can be challenging to nail down a cause for ongoing lethargy. Once the cause of lethargy is determined, it is important to follow the treatment plan prescribed by your healthcare provider to feel better and reduce your risk for any potential complications.

Frequently Asked Questions

  • What does lethargic mean?

    A person who appears sluggish, severely fatigued, and shows a lack of energy is referred to as lethargic. They may also experience depression, a lack of motivation, forgetfulness, difficulty concentrating, drowsiness, and more.

  • What does listless mean?

    Listless is another way to describe a lack of energy. Listlessness is considered a symptom of lethargy.

  • Should I be concerned about a lethargic baby?

    Lethargy in a baby is a serious concern. It may be difficult to tell whether a baby is lethargic or just drowsy from sleeping. If they seem less alert, don't smile, are too weak to cry, have difficulty waking up, or show a fever greater than 102 degrees F, they should be immediately brought to a healthcare professional.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Mount Sinai. Fatigue.

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  4. National Library of Medicine. Medline Plus. Dehydration.

  5. American Thyroid Association. Hypothyroidism.

  6. National Library of Medicine. Medline Plus. Autoimmune diseases.

  7. National Institute of Mental Health. Depression.

  8. Spathis A, Fife K, Blackhall F, et al. Modafinil for the treatment of fatigue in lung cancer: Results of a placebo-controlled, double-blind, randomized trial. Journal of Clinical Oncology 2014 32:18, 1882-1888. doi:10.1200/JCO.2013.54.4346

  9. Johns Hopkins Medicine. When to call for help.

  10. Seattle Children's Hospital. Emergency symptoms not to miss.

Additional Reading

By Lana Barhum
Lana Barhum has been a freelance medical writer since 2009. She shares advice on living well with chronic disease.