Lethargy

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Introduction

What is lethargy?

Lethargy can be described as tiredness, weariness, fatigue, or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overworking, stress, lack of exercise, or boredom. When part of a normal response, lethargy often resolves with rest, adequate sleep, decreased stress, and good nutrition.

Persistent lethargy that does not resolve with self-care may be an indication of an underlying physical or psychological disorder. Common causes include allergies, asthma, anemia, cancer and its treatments, chronic pain, heart disease, infection, depression, eating disorders, grief, sleeping disorders, thyroid problems, medication side effects, alcohol use, or drug use.

The cause of lethargy may be suggested by its pattern and accompanying symptoms. If it starts in the morning and lasts all day, it could be due to lack of sleep or depression. If it develops as the day passes and is accompanied by dry skin, constipation, cold sensitivity, and weight gain, it may be caused by an underactive thyroid gland. The combination of shortness of breath and lethargy could be due to heart or lung problems. Persistent lethargy with no clear diagnosis may result from chronic fatigue syndrome, which can start with a flu-like illness and is often not relieved with rest.

The first step in establishing the cause of lethargy is an examination by a physician. The goal of any clinical evaluation for lack of energy is to identify the root cause(s) for the condition. Diagnostic testing may be necessary in order to establish a definitive diagnosis. These tests may include blood and urine tests, imaging tests, and, in some cases, referral to a specialist. The treatment and prognosis of lethargy depend on the underlying cause.

Lethargy by itself is rarely an emergency; however, if it develops suddenly or is accompanied by other serious symptoms it may require immediate evaluation to avoid significant complications. Seek immediate medical care (call 911) for sudden energy loss, dizziness, chest pain, confusion, blurred vision, high fever, decreased urine output, sudden swelling or weight gain, shortness of breath, rapid heart rate, altered level of consciousness, severe pain, or if you think you might be a danger to yourself or others.

If your lethargy is persistent or causes you concern, seek prompt medical care.

Symptoms

What other symptoms might occur with lethargy?

Lethargy may accompany other symptoms that vary depending on the underlying disease, disorder or condition. Lethargy is a nonspecific symptom, so identifying other symptoms may be helpful in determining its cause.

Heart and lung symptoms that may occur along with lethargy

Lethargy may accompany other symptoms affecting the heart or lungs including:

  • Abnormal heart rhythms
  • Chest pain
  • Cough
  • Dizziness
  • Rapid heart rate
  • Shortness of breath (worsens with exertion)
  • Wheezing

Other symptoms that may occur along with lethargy

Lethargy may accompany symptoms related to other body systems including:

  • Anxiety
  • Appetite changes
  • Changes in bowel movements
  • Changes in urination
  • Depressed mood
  • Fever
  • Feeling very thirsty
  • Hair loss
  • Musculoskeletal pain
  • Skin changes
  • Sneezing
  • Unintentional weight gain or loss
  • Weakness

Serious symptoms that might indicate a life-threatening condition

In some cases, lethargy may be a symptom of a life-threatening condition that should be immediately evaluated in an emergency setting. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms including:

Causes

What causes lethargy?

Lethargy can be a normal response to inadequate sleep, overexertion, overworking, stress, lack of exercise, or boredom. When part of a normal response, lethargy often resolves with rest, adequate sleep, decreased stress, and good nutrition. Persistent lethargy that does not resolve with self-care may be due to a variety of diseases, disorders or conditions.

Heart- and lung-related causes of lethargy

Lethargy may be caused by heart and lung problems including:

Psychosocial and neurological causes of lethargy

Lethargy may be caused by psychosocial or neurological conditions including:

  • Alcohol use

  • Anxiety disorders

  • Dementia

  • Depression

  • Drug abuse

  • Eating disorders

  • Grief

  • Lack of exercise

  • Overwork

  • Work shift changes

Other causes of lethargy

Lethargy can also be caused by diseases, disorders or conditions including:

Serious or life-threatening causes of lethargy

In some cases, lethargy may be a symptom of a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These include:

  • Acute decompensated heart failure (rapid deterioration of the heart’s ability to pump blood)

  • Arrhythmia (abnormal heart rhythm)

  • Drug overdose

  • Electrolyte (salt) imbalances

  • Hemorrhage or internal bleeding

  • Leukemia (blast crisis)

  • Severe depression

  • Severe infection

  • Trauma

Questions for diagnosing the cause of lethargy

To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your lethargy including:

  • When did you first notice your lethargy?

  • What kind of sleep are you getting?

  • How often is lethargy affecting you?

  • Do you have any stress in your life?

  • How is your mood?

  • What is your schedule like?

  • What is your diet like?

  • What kind of exercise do you get?

  • Do you have any other symptoms?

  • What medications are you taking?

  • Do you drink any alcohol?

  • Do you use any illicit drugs?

What are the potential complications of lethargy?

Because lethargy can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan that you and your health care professional design specifically for you to reduce the risk of potential complications including:

  • Abnormal menstrual periods or infertility

  • Depression

  • Drug overdose

  • Disability

  • Isolation

  • Persistent symptoms

  • Progressive heart, lung, liver or kidney disease

  • Spread of cancer

  • Spread of infection

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2018 Dec 26
  1. Fatigue. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/003088.htm.
  2. Depression. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/003213.htm.
  3. Ricci JA, Chee E, Lorandeau AL, Berger J. Fatigue in the U.S. workforce: prevalence and implications for lost productive work time. J Occup Environ Med 2007; 49:1.
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