Lethargy is more than just feeling tired. People who have to wake up extra early to catch a flight or get home from work late after a grueling day often feel tired. Lethargy, however, is often prolonged and affects not only energy levels but also motivation and the ability to concentrate. Often, lethargy is a symptom of a larger issue or illness.

What Is Lethargy?

Lethargy is a state of reduced awareness and alertness paired with extreme tiredness. While lethargy is usually relatively mild, it can last for a prolonged period and can be disruptive to a person's quality of life. Lethargy usually has a treatable underlying cause. The first step in treatment is to identify this cause.

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Lethargy vs. Fatigue

While lethargy and fatigue are often used interchangeably, they are not the same. Fatigue is a feeling of weariness, lack of motivation, irritability, or sleepiness that results from a period of physical or mental activity, rather than an illness. The symptoms someone experiences with lethargy and fatigue are similar, but the causes are different.

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Anemia occurs when the body does not have enough red blood cells to deliver sufficient oxygen to the systems. There are a few types of anemia, each with a different cause. Aplastic anemia develops when the body stops making enough red blood cells. Iron deficient anemia results from low iron and vitamin deficient anemia from low folate, vitamin B12, and vitamin C. When the body does not get enough oxygen, lethargy and weakness are common.

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Anxiety and Depression

Anxiety and depression both cause changes in sleeping patterns, which can have significant effects on the body. People with these conditions often have trouble relaxing and feel nervous and on edge much of the time. Someone experiencing anxiety or depression may not get enough restorative sleep, which leads to prolonged periods of lethargy, weakness, and general lack of motivation.

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COPD and Emphysema

Emphysema is one of the contributing factors of chronic obstructive pulmonary disease (COPD), chronic inflammation of the lungs that leads to difficulty breathing, increased mucus production, coughing, and wheezing. Emphysema specifically affects the alveoli, small air sacs in the lungs at the ends of the bronchioles. It occurs as a result of exposure to irritants like cigarette smoke or other particulates. COPD and emphysema make it difficult for the body to get enough oxygen, which leads to lethargy.

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Lethargy is one of the defining symptoms of fibromyalgia, a disorder characterized by musculoskeletal pain and issues with mood and memory. Researchers believe that fibromyalgia is caused by how the brain interprets pain signals from the body. Research suggests it may be linked to anxiety and depression, which can also contribute to the feelings of lethargy that accompany this condition.

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Heart Disease

Heart disease is not a single ailment but a range of conditions that affect the heart, including coronary artery disease, arrhythmias, and congenital heart defects. All of these conditions affect the ability of the heart to effectively pump blood containing the essential oxygen and nutrients the body needs. Extreme lethargy can be a sign of heart disease because this lack of sufficient blood flow deprives the body of components it needs to function normally.

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Sleep Apnea

Sleep apnea causes a person's breathing to stop and start repeatedly while sleeping. There are different types of sleep apnea. Obstructive sleep apnea is the most common form and happens when the throat muscles relax during sleep, blocking the airway. Central sleep apnea occurs when incorrect signals are sent from the brain to the body, but the muscles used for breathing do not function properly. Complex sleep apnea occurs when someone experiences a combination of the two. Lethargy is one of the main signs of sleep apnea, particularly when the person feels lethargic even after a full night's sleep.

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Thyroid Issues

Thyroid hormones are secreted into the blood and travel to every tissue in the body. They help the body use energy and keep organs functioning properly. Hypothyroidism occurs when the body does not make enough thyroid hormone, which drastically affects energy processing. Lethargy is one of the main symptoms of hypothyroidism. Interestingly, hyperthyroidism, when the thyroid produces excessive thyroid hormones, also causes fatigue as a result of sleep disturbances from tachycardia, anxiety, and tremors.

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Anyone who consistently gets a full night of sleep and still feels lethargic in the morning should see their doctor to rule out any underlying problems. The cause of the lethargy determines the treatment. For example, if lethargy is due to hypothyroidism, the doctor will likely prescribe synthetic thyroid hormones. Supplements can be given to correct deficiencies causing anemia and BIPAP or CPAP machines can correct sleep apnea.

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