Fatigue is different from drowsiness. Drowsiness is feeling the need to sleep. Fatigue is a lack of energy and motivation. Drowsiness and apathy (a feeling of not caring about what happens) can be symptoms that go along with fatigue.

Fatigue can be a normal and important response to physical activity, emotional stress, boredom, or lack of sleep. Fatigue is a common symptom, and it is usually not due to a serious disease. But it can be a sign of a more serious mental or physical condition. When fatigue is not relieved by enough sleep, good nutrition, or a low-stress environment, it should be evaluated by your health care provider.

There are many possible causes of fatigue, including:

• Anemia (including iron deficiency anemia)
• Depression or grief
• Iron deficiency (without anemia)
• Medicines, such as sedatives or antidepressants
• Persistent pain
• Sleep disorders such as insomnia, obstructive sleep apnea, or narcolepsy
• Thyroid gland that is underactive or overactive
• Use of alcohol or drugs, such as cocaine or narcotics, especially with regular use

Fatigue can also occur with the following illnesses:

• Addison disease (a disorder that occurs when the adrenal glands don't produce enough hormones)
• Anorexia or other eating disorders
• Arthritis, mainly adult or juvenile rheumatoid arthritis
• Autoimmune diseases such as systemic lupus erythematosus
• Cancer
• COVID-19
• Diabetes
• Fibromyalgia
• Heart failure
• Infection, especially one that takes a long time to recover from or treat, such as bacterial endocarditis (infection of the heart muscle or valves), parasitic infections, hepatitis, HIV/AIDS, tuberculosis, and mononucleosis
• Kidney disease
• Liver disease
• Malnutrition

Certain medicines may also cause drowsiness or fatigue, including antihistamines for allergies, blood pressure medicines, sleeping pills, steroids, and diuretics (water pills).

Chronic fatigue syndrome (CFS) is a condition in which symptoms of fatigue persist for at least 6 months and do not resolve with rest. The fatigue may be worsened with physical activity or mental stress. It is diagnosed based on the presence of a specific group of symptoms and after all other possible causes of fatigue are ruled out.

Here are some tips for reducing fatigue:

• Get enough sleep each night.
• Make sure your diet is healthy and well-balanced, and drink plenty of water throughout the day.
• Exercise regularly.
• Learn better ways to relax. Try yoga or meditation.
• Maintain a reasonable work and personal schedule.
• Change or reduce your stressors, if possible. For example, if you are able, take a vacation or resolve relationship problems.
• Discuss with your provider whether any supplemental vitamins might help you.
• Avoid alcohol, nicotine, and drug use.

If you have long-term (chronic) pain or depression, treating it often helps the fatigue. Be aware that some antidepressant medicines may cause or worsen fatigue. If your medicnie is one of these, your provider may have to adjust the dosage or switch you to another medicine. DO NOT stop or change any medicines without first talking to your provider.

Stimulants (including caffeine) are not effective treatments for fatigue. They can make the problem worse when they are stopped. Sedatives also tend to worsen fatigue.

Contact your provider right away if you have any of the following:

• Confusion or dizziness
• Blurred vision
• Little or no urine output
• Recent swelling and weight gain
• Thoughts of harming yourself or of suicide

Contact your provider for an appointment if you have any of the following:

• Unexplained weakness or fatigue, especially if you also have a fever, unintentional weight loss, or regular sweats
• Constipation, dry skin, weight gain, or you cannot tolerate cold
• Wake up and fall back to sleep many times during the night
• Frequent headaches
• Are taking medicines, prescribed or non-prescribed, or using drugs that may cause fatigue or drowsiness
• Feel sad or depressed
• Insomnia

You will be asked about your medical history, fatigue symptoms, and your lifestyle, habits, and feelings.

Your provider will likely perform a complete physical examination, paying special attention to your heart, lymph nodes, thyroid, abdomen, and nervous system.

Tests that may be ordered include the following:

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

Treatment depends on the cause of your fatigue symptoms.

Tiredness; Weariness; Exhaustion; Lethargy

Clauw DJ. Fibromyalgia. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 253.

Regehr J. Fatigue. In: Kellerman RD, Rakel DP, Heidelbaugh JJ, Lee EM, eds. Conn's Current Therapy 2023. Philadelphia, PA: Elsevier 2023:14-15.

Seller RH, Symons AB. Fatigue. In: Seller RH, Symons AB, eds. Differential Diagnosis of Common Complaints. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 14.

Updated by: Jacob Berman, MD, MPH, Clinical Assistant Professor of Medicine, Division of General Internal Medicine, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.