Fatigue is a common symptom. Almost everyone feels it during short-term illness. Fortunately, fatigue usually goes away when the illness is over.

But sometimes fatigue doesn’t go away. It doesn’t get better with rest. And the cause might be unclear.

Fatigue reduces energy, the ability to do things and the ability to focus. Ongoing fatigue affects quality of life and state of mind.

Causes

Most of the time fatigue can be traced to one or more lifestyle issues, such as poor sleep habits or lack of exercise. Fatigue can be caused by a medicine or linked to depression. Sometimes fatigue is a symptom of an illness that needs treatment.

Lifestyle factors
Fatigue may be related to:

Alcohol or drug use
Eating poorly
Medicines, such as ones used to treat allergies or coughs
Not enough sleep
Too little physical activity
Too much physical activity
Conditions
Exhaustion that doesn’t let up might be a sign of:

Adrenal insufficiency
Amyotrophic lateral sclerosis (ALS)
Anemia — a condition in which the body doesn’t get oxygen due to a lack of healthy red blood cells.
Anxiety disorders
Cancer
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)
Chronic infection or inflammation
Chronic kidney disease
COPD (chronic obstructive pulmonary disease) — the blanket term for a group of diseases that block airflow from the lungs — including emphysema.
Coronavirus disease 2019 (COVID-19)
Depression (major depressive disorder) or other mood disorders
Diabetes
Fibromyalgia
Grief
Heart disease
Heart failure
Hepatitis A
Hepatitis B
Hepatitis C
HIV/AIDS
Hyperthyroidism (overactive thyroid)
Hypothyroidism (underactive thyroid)
Inflammatory bowel disease (IBD)
Liver disease
Low vitamin D
Lupus
Medicines and treatments, such as chemotherapy, radiation therapy, pain medicines, heart medicines and antidepressants
Mononucleosis
Multiple sclerosis
Obesity
Parkinson’s disease
Physical or emotional abuse
Polymyalgia rheumatica
Pregnancy
Rheumatoid arthritis
Sleep apnea — a condition in which breathing stops and starts many times during sleep.
Stress
Traumatic brain injury

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