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

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

  • DepressionApathy (lack of interest in or enthusiasm for things)Lack of motivationFeeling less alertCognitive difficulties (forgetfulness and trouble concentrating)Severe drowsiness

Other symptoms that may accompany lethargy include:

  • Aches and pains that won’t go away despite treatmentSleep problemsSensitivity to hot and cold temperaturesEye inflammationChronic fatigue lasting more than two weeksSwollen neck glandsUnexplained weight changesFeeling 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:

  • Adrenal problems
  • Anemia
  • Autoimmune disorders
  • Cancer
  • Chronic fatigue syndrome
  • Depression
  • Fibromyalgia
  • Hyperthyroidism
  • Hypothyroidism
  • Hydrocephalus (brain swelling) or brain injuries
  • Kidney failure
  • Meningitis
  • Pituitary diseases

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.

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

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 infectionKidney function testsLiver function testsThyroid function testsUrinalysis

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 painAltered consciousnessBlurred visionChest painConfusionFacial paralysisHigh feverInability to move arms and legsNausea and vomitingRapid heart rateSevere dizzinessSevere headacheSevere painShortness of breathSignificant changes in behavior (including thoughts of self-harm)Slurred speechSudden and severe swellingSudden energy loss

Summary

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.

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:

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.

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.

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

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.