Fatigue is not the same as being tired. When you are tired, you still have some energy. You may be short-tempered, forgetful, or impatient, but you can generally make it through the day.

Fatigue, on the other hand, is more serious. It is more than just physical tiredness. It tends to last much longer, and you feel so drained that it begins to interfere with your everyday life. You may have an overwhelming urge to sleep and rarely feel rested when you wake up. Many things can cause fatigue; some are much more serious than others.

Lifestyle Habits

Lifestyle factors are one of the most common causes of temporary fatigue. Although these habits are all things you can fix, some take time and effort.

Habits most likely to cause fatigue are alcohol or drug use, an unhealthy diet, or having poor sleep habits and never getting enough rest. Both too much physical activity and a sedentary lifestyle can cause fatigue, and people who travel often experience fatigue as jet lag.

exhausted man on hotel bed has jet lag



A poor diet can lead to vitamin deficiencies, which can cause fatigue. For example, an iron deficiency can lead to anemia, where there are not enough healthy red blood cells to deliver oxygen to the body. You may have an iron deficiency if you do not eat foods rich in iron, like red meat, rice, eggs, or beans.

Other deficiencies can cause fatigue, too. A vitamin B12 deficiency affects the health of red blood cells, and a vitamin D deficiency drains muscle and bone strength.

exhausted looking woman has iron deficiency anemia


Weight Problems and Eating Disorders

Weight problems and eating disorders can lead to fatigue. Obesity fatigue results from having a sedentary lifestyle. When you are overweight and spend a lot of time sitting, your body stiffens. When you try to get up and move again, you experience aches and pains, making it more difficult to move and adding to the problem.

Eating disorders, like anorexia nervosa and bulimia, can lead to deficiencies, and studies show that eating disorders are related to disrupted sleep.

exhausted woman with empty plate beside her; eating disorder concept


Hormonal Imbalances

Hormones are chemical messengers controlled by the endocrine system that signal hundreds of bodily processes. When hormones are imbalanced due to a problem with any part of the endocrine system, it results in fatigue.

The most common endocrine problem that causes fatigue is hypothyroidism. The thyroid gland makes thyroid hormone, which controls how your body uses energy. If the gland does not produce enough, bodily processes slow down, causing fatigue.

doctor checking patient's thyroid


Sleep Disorders

A variety of sleep disorders can cause fatigue to the point where the person feels very sleepy during the day and falls asleep at inappropriate times. Some common sleep disorders include insomnia, which is when you have a hard time falling or staying asleep, and narcolepsy, when you have feelings of extreme tiredness during the day and fall asleep suddenly.

Conditions that prevent you from getting a good night's sleep can cause fatigue, too. For example, sleep apnea causes abnormal breathing patterns while you sleep, and restless leg syndrome causes the urge to move your legs while you try to fall asleep.

woman lying awake in bed; insomnia concept


Medications and Treatments

Many types of medication can cause fatigue. Some common over-the-counter medications, like antihistamines in allergy medications, lead to fatigue.

Prescription medications can as well, including those to treat high blood pressure, depression, seizures, and anxiety, and pain medications and muscle relaxants. Fatigue is also a common side effect of chemotherapy and bone marrow transplants.

woman with fatigue surrounded by medications


Mental Health Conditions

Fatigue is also a symptom of several mental health conditions, including common ones like anxiety and depression. It is a sign of multiple types of depressive disorders, including major depression, persistent depressive disorder, and premenstrual dysphoric disorder.

Conditions that lead to sleep disturbances, like post-traumatic stress disorder, can also cause fatigue.

unhappy looking man lying on his bed


Autoimmune Disorders

Autoimmune disorders happen when the body mistakenly attacks its own healthy cells. There are more than 80 autoimmune diseases, including rheumatoid arthritis, psoriasis, lupus, psoriatic arthritis, and type 1 diabetes.

Although each of these affects the body differently, many of them have overlapping symptoms, one of the most common of which is fatigue.

chalkboard that says autoimmune disese


Heart and Lung Problems

Any condition that affects the heart or lungs can cause fatigue. This includes severe heart conditions:

  • those that affect the blood vessels, like coronary artery disease
  • those that affect the heart muscle, like cardiomyopathy
  • those that affect the valves, like endocarditis.

Lung conditions like emphysema and COPD also cause fatigue because they affect how oxygen gets into the blood. To learn more about symptoms of COPD, see our Facty article on the topic.

woman lying on the couch having lung issues trouble breathing


Disease and Infection

Many diseases and infections can cause fatigue. Some, like the flu, are more common and mild, while others are more serious.

Severe fatigue that does not resolve can be a sign of cancer. Chronic kidney disease can lead to chronic fatigue, and studies show it can delay recovery and increase mortality. People with HIV deal with fatigue, particularly if they have had the virus for many years. Various factors may be to blame, including HIV medication, pain medications, depression, anxiety, and the effects of the virus itself.

sick man in bed with chills and fatigue


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This site offers information designed for educational purposes only. You should not rely on any information on this site as a substitute for professional medical advice, diagnosis, treatment, or as a substitute for, professional counseling care, advice, diagnosis, or treatment. If you have any concerns or questions about your health, you should always consult with a physician or other healthcare professional.