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Top Causes of Fatigue

If you’re feeling overly tired, you may have an underlying problem that’s making you sleepy.
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Written by Priyanka Gimbel, MD, MPH.
K Health - Telemedicine
Last updated January 23, 2024

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What is fatigue?

Adults need roughly 7 to 9 hours of sleep every night, though some do fine on 6 hours and others need as many as 10. Yet about 30% of people say they get less than 6 hours of sleep a night, according to the Centers for Disease Control and Prevention (CDC).

More than 70 million Americans suffer from chronic sleep problems like insomnia.

Fatigue can feel like sleepiness, tiredness, or physical weakness. Other signs of fatigue are not being able to concentrate, being forgetful, or feeling emotionally drained, moody, or irritable.

A number of illnesses can make you feel tired, from the everyday flu or sore throat to depression or thyroid issues.

A handful of chronic illnesses can also make you feel fatigued, like chronic obstructive pulmonary disease and fibromyalgia.

Treatment usually involves improving sleep hygiene, supplements, or medication.

Sleep hygiene—habits that affect the quality of your sleep—is important for getting adequate sleep. Good sleep hygiene means:

  • Making sleep a priority
  • Sleeping in complete darkness
  • Avoiding late-night eating and drinking
  • Not using electronics close to bed time
  • Going to bed early so you can get at least 7 hours of deep restorative sleep

1. Sleep deprivation

Pro Tip

Make sure you have good sleep hygiene. Many people read on their tablets or other electronics before bed, watch TV in their bedroom, or look at their phones shortly before bed. Try to avoid these activities at least 30 minutes prior to when you hope to go to bed. —Dr. Priyanka Gimbel


People can be sleep deprived if they don’t have the opportunity to get enough sleep. This can happen to new parents, who have to get up frequently to take care of a newborn, or if the demands of school or work interfere with sleep.

Some medical conditions can cause sleep deprivation, such as obstructive sleep apnea, insomnia, or restless leg syndrome.

Treatment involves establishing good sleep hygiene habits and seeing a doctor to rule out medical reasons for your sleep deprivation.

2. Obstructive sleep apnea


  • Excessive daytime fatigue
  • Snoring
  • Waking up at night gasping for air
  • Waking up with a headache
  • Frequent urination during the night
  • Insomnia

Obstructive sleep apnea (OSA) happens when your airways become blocked during sleep. This happens when the tongue or other muscles in the palate relax and fall back during sleep. OSA leads to snoring and frequent awakenings throughout the night as the body tries to overcome the obstruction.

OSA is a common condition, particularly in obese male adults. Your doctor may order a sleep study, conducted at home or at a hospital, to diagnose it.

Treatment includes weight loss and avoiding alcohol and medications that can worsen sleep apnea. Many people need to use a CPAP machine, which pushes air into the airways to keep them open while you sleep.

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  • Prescription medications and supplies shipped to your door

3. Insomnia


  • Fatigue and daytime sleepiness
  • Difficulty falling asleep or staying asleep
  • Frequent worrying about sleep
  • Having a hard time concentrating or remembering things you have to do
  • Feeling depressed, anxious, or irritable
  • Decreased energy and motivation

Insomnia is when you have difficulty falling asleep or staying asleep. It can be a short-term or chronic condition.

Insomnia is often a symptom of depression and anxiety, but can also be related to chronic pain, alcohol or substance use, heart and lung diseases, and certain medications. Sometimes, insomnia is a symptom of other sleep disorders like sleep apnea.

Insomnia is difficult to treat, but treatment approaches include cognitive behavioral therapy, sleep hygiene, and medication.

4. Iron-deficiency anemia

Pro Tip

Fatigue is not always related to sleep problems. It can sometimes be due to multiple underlying causes. There are tests that we can perform to rule in or rule out certain causes of fatigue. —Dr. Gimbel


  • Feeling tired or weak
  • Craving ice or items with no nutritional value
  • Headaches
  • Dizziness or lightheadedness
  • Difficulty breathing at rest or with light activity
  • Unable to exercise at full strength
  • Heart palpitations

There are several different types of anemia, but iron deficiency anemia is the most common. It happens when the body does not have enough iron to form hemoglobin, the protein in red blood cells that carries oxygen throughout the body.

Iron deficiency anemia is caused by blood loss, not getting enough iron, an inability to adequately absorb iron in the body, or pregnancy. Some conditions that can lead to iron deficiency anemia include:

  • Following a strict vegan or vegetarian diet
  • Celiac disease
  • Stomach inflammation
  • Bacterial infections
  • Bariatric surgery
  • Heavy menstrual periods
  • Excess calcium or caffeine intake.

Treatment focuses on iron supplements and treating any associated medical conditions.

5. Hypothyroidism


Hypothyroidism means the thyroid gland is underactive and doesn’t produce enough thyroid hormones. This causes your metabolism to slow down.

It can happen because of an autoimmune disease, surgery or radiation to the thyroid gland, some medications, or pregnancy. If not treated, the symptoms can become very serious, leading to confusion, a very low heart rate, low body temperature, and even coma.

Hypothyroidism is easily managed with a daily oral medication. It is important that your doctor monitor you and test your blood routinely to keep the medication at the correct levels.

6. Depression


  • Fatigue
  • Depressed mood
  • Loss of interest in most or all activities
  • Change in weight or appetite
  • Irritability
  • Difficulty concentrating
  • Feelings of worthlessness or guilt
  • Suicidal thoughts

Depression is a mood disorder in which someone feels sad or loses interest in things they used to care about. You may be depressed if you feel this way most of the day on nearly every day of the week. These symptoms can get in the way of daily life, work, and relationships. It also can cause fatigue even if you’re sleeping a lot.

Treatment often includes psychotherapy with or without antidepressant medications.

7. Fibromyalgia


  • Fatigue
  • Sleeping problems
  • Pain in multiple sites of the body
  • Cognitive changes, known as “fibromyalgia fog”
  • Depression and/or anxiety
  • Headaches
  • Numbness or tingling in the arms and/or legs

Fibromyalgia is a set of chronic symptoms that includes constant fatigue, tenderness to touch, and musculoskeletal pain. Doctors don’t know why it happens.

The majority of people with fibromyalgia are women. Often, they also have other conditions such as irritable bowel syndrome, chronic pelvic pain, psychiatric disorders, and autoimmune conditions like rheumatoid arthritis.

Treatment includes education about fibromyalgia, good sleep hygiene, an exercise regimen, medication, and managing underlying other conditions.

8. Chronic obstructive pulmonary disease (COPD)


  • Fatigue
  • Chronic cough with mucus, usually related to smoking
  • Shortness of breath
  • Wheezing
  • Chest tightness

Chronic obstructive pulmonary disease (COPD) is a progressive inflammation of the lungs that makes it hard to breathe. It is most often caused by long-term exposure to smoking tobacco. However, frequent exposure to dusts, vapors, and pollution can also increase your risk.

Symptoms may take years to develop. COPD is commonly misdiagnosed, so it's important to see your doctor if you have symptoms and get tested. Treatment is crucial as COPD increases your risk for heart disease and lung cancer.

COPD cannot be cured, but you can improve your quality of life by:

  • Quitting smoking
  • Avoiding exposure to other lung irritants
  • Using inhalers and other lung medications
  • Exercising
  • Getting flu and pneumonia vaccines

Other possible causes

A number of conditions may also cause fatigue, though these are either rare or fatigue is not usually the defining symptom. They include:

  • Infections
  • Electrolyte deficiencies
  • Kidney or liver problems
  • Hyperthyroidism
  • Certain medications
  • Substances like marijuana or alcohol
  • Autoimmune disorders (e.g., multiple sclerosis, rheumatoid arthritis, lupus, Sjӧgren’s)
  • Cancer

When to call the doctor

Dr. Rx

If a patient is complaining about not feeling refreshed after sleeping or having a hard time sleeping—I think about sleep deprivation, insomnia, obstructive sleep apnea, restless leg syndrome, or other sleeping disorders. If they are already practicing good sleep hygiene, I would consider referring them to a sleep medicine doctor to do a sleep test that would help us determine the exact cause. —Dr. Gimbel

Call your primary care physician if you experience any of the following:

  • Fatigue that is not getting better despite good sleep hygiene
  • Symptoms of a mood disorder, such as anxiety or depression
  • Body or muscle aches
  • Snoring or frequent night awakenings
  • A cough that will not go away
  • Changes in appetite or weight
  • Irregular menstrual cycle
  • Frequent headaches
  • Difficulty concentrating

Should I go to the ER for fatigue?

You should go to the emergency department if you have any of these signs of a more serious problem.

  • Suicidal thoughts
  • Fever (100.4℉ or greater)
  • Difficulty breathing
  • Lightheadedness or dizziness
  • Chest pain or heart palpitations

Fatigue treatments

At-home care

You can try to get more sleep by improving your sleep hygiene. That includes:

  • Stick to a schedule, particularly going to sleep and waking up around the same time every day.
  • Avoid naps in the late afternoon or evening.
  • Don’t eat too close to bedtime (within 2 hours).
  • Avoid caffeine, especially in the afternoon.
  • Avoid alcohol.
  • Avoid sleeping pills, unless recommended by your doctor.
  • Limit blue light, including phones, TVs, and other electronics 2 to 3 hours before going to bed.
  • Use blackout curtains to eliminate light that might filter through windows.
  • Try to exercise in the morning or afternoon, but not in the evening.
  • Get sun exposure in the mornings. This helps set your circadian rhythm (body clock).
  • Sleep in a cool room, ideally between 60 to 67℉.

Other treatment options

  • Try to maintain a healthy body mass index or BMI (ideally 18.5 to 24.9 kg/m2).
  • Stop smoking tobacco and marijuana.
  • Minimize exposure to dust, fumes, and vapors at work and home.
  • Sleep on your side if you snore on your back.
  • Get regular exercise.
  • Schedule a yearly physical for blood tests and other screening tests.
Illustration of a healthcare provider asking questions on a smart phone.
Virtual weight loss solution
A personalized GLP-1 medication program (eg. Wegovy, Ozempic) delivered to you via our partner Korb Health
Illustration of a healthcare provider asking questions on a smart phone.
  • Free consultation; program starts at $269/mo
  • Checkmark Inside Circle.Customized online program and wellness coaching
  • Prescription medications and supplies shipped to your door
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The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
K Health - Telemedicine
Dr. Gimbel is a board-certified Family Medicine physician and writer/reviewer for Buoy Health. She received her undergraduate degree in Neuroscience with a minor in Sociology from the University of Illinois at Chicago (2008) and graduated from the University of Illinois at Chicago College of Medicine and School of Public Health (2013). She completed a family medicine residency at the University of...
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