Common Causes of Fatigue

Why am I always tired?
Verywell / Brianna Gilmartin

If you find yourself sleeping until the last possible second before dragging yourself out of bed, you may be wondering, "Why am I always tired?" Or maybe you just don't have the energy to get things done the way you once did. Fatigue and a lack of energy are a big problem for many people, but these problems can only be addressed if you know what is wrong.


Common Causes of Fatigue

If you are feeling constantly tired, the first thing you should do is see your personal physician for a checkup. Your doctor can take a careful history, perform a physical exam, and do any needed testing to determine the cause of your fatigue.

A few of the possible causes of fatigue include the following:


Lack of Sleep

Senior man in his early 60s with greying beard is sick and sleepless in bed while night.

While a lack of sleep may seem to be an obvious cause of chronic fatigue, it is a surprisingly common reason for feeling tired. Many people go through life feeling too stressed or too busy to slow down and get all of the sleep that they need to feel good.

While a lack of sleep isn't a medical condition per se, your doctor may be able to help you learn about ways to reduce your stress or prescribe medications to help you with occasional sleeplessness.

It's helpful to begin by determining your sleep needs. The "average" adult needs around eight hours per night, but few people are average. You may also have a sleep debt you have accumulated, and this requires extra sleep to catch up.



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Depression is a condition believed to be caused abnormalities in mood-regulating chemicals called neurotransmitters in the brain.

People with depression tend to have problems with sleep and energy level. They may have trouble falling asleep or wake up during the night. Some people with depression may also have trouble waking up in the morning and sleep too long. Depression often makes people feel sluggish and unmotivated.

Some of the other symptoms of depression include feeling sad or empty, losing interest in activities that you once enjoyed, changes in appetite or weight, feeling worthless or guilty, and having recurring thoughts of death or suicide.

If you are having suicidal thoughts, contact the National Suicide Prevention Lifeline at 1-800-273-8255 for support and assistance from a trained counselor. If you or a loved one are in immediate danger, call 911. 

For more mental health resources, see our National Helpline Database.

If you feel like you may be depressed, talk to your doctor. She may recommend that you also see a therapist who can help you work through your feelings. Untreated depression not only leads to tiredness but can affect every aspect of your life.



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When you have anemia, your body either has a lower than normal number of red blood cells or it doesn't have enough hemoglobin. Hemoglobin is the substance which gives red blood cells their color. It is also involved in carrying oxygen throughout your body.

When you have too little hemoglobin or not enough red blood cells, your body doesn't get enough oxygen so you feel tired or weak. You may also have symptoms such as pale skin, shortness of breath, dizziness, or headaches.

Iron deficiency alone, even without anemia, is now thought to be a cause of chronic fatigue.

 A simple blood test at your doctor's office can tell you whether or not you have anemia. Keep in mind that anemia is not just iron deficiency and there are a great many possible causes.



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Hypothyroidism is a disease in which thyroid gland does not produce enough thyroid hormone. Thyroid disease is very common, especially in women, and affects 27 to 60 million people in the United States alone.

Thyroid hormones control your metabolism so that when levels are low, you may have symptoms of tiredness, weight gain, and feeling cold.

Making the condition even more confusing, hypothyroidism can mimic depression symptoms.

Thankfully, a simple blood test can determine if your thyroid gland is functioning up to par, and treatment can be instituted if not.


Heart Disease

Doctor talking to patient in office

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Heart disease, especially heart failure, can cause you to feel tired all of the time and unable to tolerate exercise. With heart failure, ​the heart is less effective in pumping oxygenated blood to muscles and other tissues in the body. Even your regular daily activities, like walking or carrying your groceries in from the car, can become difficult.

Other possible symptoms of heart disease include chest pain, palpitations, dizziness, fainting, and shortness of breath.

In recent years it's been noted that the symptoms of heart disease in women often differ from those in men and may be more subtle, for example, presenting as fatigue rather than chest pain. It's thought that this lack of recognition of heart disease in women is a reason why women are more likely than men to die from the disease.

It's important to talk to your doctor about all of your symptoms as well as your family history of medical conditions. Based on these findings, you and your doctor may decide that further tests to evaluate your heart are needed.


Sleep Apnea

Woman sleeping with pillow over head
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Sleep apnea is a chronic condition in which there may be pauses in breathing, or shallow breathing, lasting anywhere from a few seconds to a minute while a person is sleeping. These pauses and shallow breaths can occur as many as 30 times a minute. And, each time breathing returns to normal, often with a snort or a choking sound, it can be very disruptive to a person's sleep.

This disrupted and poor quality sleep can be a common cause of daytime sleepiness.

Other symptoms associated with sleep apnea include morning headaches, memory problems, poor concentration, irritability, depression, and a sore throat upon waking.

Your doctor will likely ask you if others have noticed problems with your sleep such as irregular breathing or snoring, and may also be concerned if you have risk factors for sleep apnea or experience daytime tiredness. A sleep study is often recommended to document sleep apnea, and if present, treatments such as CPAP may be recommended.

It's important to note that untreated sleep apnea not only results in tiredness, but can lead to heart disease, stroke, or even sudden death.



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Hepatitis is an inflammation of the liver with several possible causes ranging from infections to obesity.

The liver serves many important functions in the body from breaking down toxins to manufacturing proteins that control blood clotting, to metabolizing and storing carbohydrates, and much more. When the liver is inflamed, these important processes can come to a halt.

In addition to being tired, some of the symptoms that you might experience with hepatitis include jaundice (a yellowish discoloration of the skin and whites of the eyes, abdominal pain, nausea, dark yellow urine, and light-colored stools.

Liver function tests are easily done in most clinics, and if abnormal, can lead you and your doctor to look for the possible causes.



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Diabetes is a condition in which either the body doesn't make enough insulin or it doesn't use it as well as it should. Insulin is a hormone produced by the pancreas that helps glucose get into the body's cells to be used for energy production. There are several reasons that diabetes may be causing you to feel tired all the time.

Other symptoms of diabetes include frequent urination, extreme thirst, unexplained weight loss, extreme hunger, sudden vision changes, tingling or numbness in the hands or feet, dry skin, slow-healing wounds or more infections than usual.

A simple blood sugar test can be done in most clinics, and a test called hemoglobin A1C can help determine what your average blood sugar has been over the past three months.


Chronic Fatigue Syndrome

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Chronic fatigue syndrome is a disorder characterized by intense fatigue that does not improve with rest and which may be made worse by physical or mental exertion. It is unknown what causes this condition.

In addition to debilitating fatigue, some of the other symptoms which define chronic fatigue syndrome include impairment in short-term memory or concentration, muscle and joint pain, headaches, tender lymph nodes, and frequent sore throat.



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Fatigue can be a side effect of several different medications. Some of the most common medications which may cause fatigue include:

  • Blood pressure medications
  • Statins and fibrates (used to treat high cholesterol)
  • Proton pump inhibitors (used to treat stomach conditions such as acid reflux)
  • Benzodiazepines (used to treat anxiety, muscle spasms, seizures)
  • Antihistamines (used to treat allergies)
  • Antidepressants (used to treat depression)
  • Antipsychotics (used to treat schizophrenia, bipolar disorder, and other serious psychiatric conditions)
  • Antibiotics (used to treat bacterial infections)
  • Diuretics (used to treat high blood pressure, glaucoma, and edema)
  • Narcotic pain medications

Your doctor or pharmacist can tell you if fatigue is a possible side effect of any medications that you are taking, both prescription and over-the-counter.

A Word From Verywell

The causes of fatigue listed above are fairly common, but there is a multitude of medical conditions which can result in fatigue. If you feel your tiredness is out of the ordinary, and you aren't simply missing out on the sleep you need to feel rested, make an appointment to see your doctor. She can take a careful history including your family history of medical conditions, perform a physical exam, and order any blood work needed to begin looking for causes.

It can be frustrating, at times, as you wait for answers to your tiredness, but don't give up. Finding a reason for your fatigue can not only result in improvement with treatment but may detect conditions which should be diagnosed for other reasons as well.

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6 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  5. Berry RB, Budhiraja R, Gottlieb DJ, et al. Rules for scoring respiratory events in sleep: update of the 2007 AASM Manual for the Scoring of Sleep and Associated Events. Deliberations of the Sleep Apnea Definitions Task Force of the American Academy of Sleep Medicine. J Clin Sleep Med. 2012;8(5):597-619. doi:10.5664/jcsm.2172

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