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Why Am I So Tired? Five Causes of Fatigue and What It Could Mean

Physical Health

March 1, 2024
Causes of Fatigue

When someone asks, “How are you?” Do you find yourself always answering with “I’m tired”?

Everyone feels tired from time to time, but what does it mean when you can’t feel refreshed no matter what you try?

Fatigue is the feeling of extreme tiredness that makes it hard for you to get through your day. Fatigue can be caused by many different things. Read on to learn more about fatigue, what causes it, and what it could mean.

What Is Fatigue?

Fatigue is more than just feeling tired on occasion. If you have fatigue, tiredness makes it difficult for you to accomplish your daily activities and doesn’t get better after you rest. You may have temporary fatigue that lasts for a few weeks or months or chronic fatigue that lasts for more than 6 months.

If you have fatigue, you can experience physical, mental, or emotional symptoms of fatigue in addition to tiredness, such as:

  • Tiredness in your whole body
  • Lack of energy
  • Tired eyes
  • Stiff or sore muscles
  • Feeling generally unwell
  • Boredom
  • Mood swings
  • Headache
  • Changes in appetite
  • Low motivation
  • Difficulty concentrating

Fatigue can be caused by many different factors. Continue reading to learn more about five possible causes of fatigue.

1. Lifestyle Factors

Lifestyle factors are habits that you have control over that can affect your health.

Sleep Deprivation

Most adults need about seven hours of sleep every night to stay healthy. If you don’t leave yourself enough time to sleep, you may wake up feeling unrefreshed and fatigued throughout the day.

You may experience the symptoms of fatigue after just one night of sleep deprivation. If sleep deprivation continues, you may experience more severe symptoms in addition to fatigue, such as:

  • Microsleeps — falling asleep for a few seconds before waking up
  • Nystagmus — uncontrolled eye movements
  • Difficulty speaking
  • Shaky hands
  • Visual hallucinations — seeing things that aren’t there
  • Impulsive behavior
  • Impaired judgment

Sleep deprivation likely affects everyone at some point in their life. Possible reasons you may not be getting enough sleep include:

  • Shift work
  • Working the night shift
  • Interrupted sleep (due to factors like a snoring partner, noisy neighbors, or children)
  • Alcohol use and misuse
  • Drinking caffeine too late in the day
  • Poor sleep hygiene (sleep habits)
  • Feeling stressed
  • Sleeping in an unfamiliar place
  • Jet lag due to travel
  • Short-term illness like the flu

Lack of Exercise

If you feel fatigued, it can be hard to get motivated to exercise. However, getting enough exercise can actually make you feel more energetic.

Research shows that regular moderate-intensity exercise (such as brisk walking) can improve fatigue symptoms.

Poor Diet

Food provides fuel for your mind and body. If you’re not fueling your body properly, you may feel fatigued. If you don’t drink enough liquid and become dehydrated, it can also cause fatigue.

Foods with lots of sugar and processed foods that contain saturated fats and nitrates may lead to fatigue. A diet lacking important nutrients can also cause more serious health concerns in addition to fatigue symptoms.

Vitamin and Mineral Deficiencies

If you don’t get enough of certain vitamins in your diet, it can cause fatigue and other medical conditions that can contribute to fatigue.

Low levels of iron and vitamin B12 can cause anemia. Anemia is a condition where you don’t have enough red blood cells (RBCs) to carry oxygen around your body. When your body doesn’t get enough oxygen delivered by your blood, you can feel fatigue. In fact, fatigue is usually the first symptom people notice when they have anemia.

Iron and vitamin B12 are found in meat and dairy. If you are vegetarian, talk to your doctor or a registered dietician about how to make sure you get enough of these essential elements in your diet to avoid fatigue.

Low levels of vitamin D can affect your bone strength and muscle strength. You can get vitamin D through exposure to the sun and in fish and dairy products.

There isn’t any evidence that taking vitamin or mineral supplements will improve fatigue if you don’t have a deficiency. Talk to your doctor before you start taking any vitamin supplements.

Eating Disorders

Eating disorders, such as anorexia and bulimia, can cause fatigue as a symptom of starvation and malnutrition.

Alcohol and Drug Use

Alcohol and drug use can contribute to fatigue by making it difficult to sleep.

Alcohol might actually help you fall asleep by slowing down your brain activity. However, alcohol interrupts your sleep cycles and doesn’t allow you to get quality sleep.

Common stimulants, such as caffeine and nicotine in tobacco products, can make it more difficult to fall asleep and stay asleep. This is especially true when consumed later in the day.

Prescription stimulants (such as amphetamine or methylphenidate) and illegal stimulants (such as cocaine and methamphetamine) can also make it hard to sleep.

2. Physical Health Conditions

Fatigue is a common symptom in several different health conditions.


Causes of Fatigue

When you have an infection, your body is under more stress than usual. It takes extra energy for your cells to fight the infection. This is why you may feel extra sleepy and fatigued when you have a bacterial, viral, or fungal infection, including:

  • Influenza (the flu)
  • COVID-19
  • Pneumonia
  • Mononucleosis (mono)
  • Human immunodeficiency virus (HIV)
  • Lyme disease

Heart and Lung Conditions

You may experience fatigue if you have a condition that affects your heart or lungs. If your heart or lungs aren’t working as well as they should, you may not be getting enough blood and oxygen delivered around your body. This can lead to feeling fatigued.

Examples of heart conditions that can cause fatigue include:

  • Congestive heart failure (CHF) — problems with how your heart squeezes and relaxes
  • Coronary artery disease (CAD) — narrowing of blood vessels due to fat deposits
  • Arrhythmias — abnormal heart rhythm
  • Heart valve disease — problems with the valves that separate the chambers of the heart
  • Congenital heart disease — heart disease you have at birth

Examples of lung conditions that can cause fatigue include:

  • Asthma — difficulty breathing caused by narrow, swollen airways
  • Chronic obstructive pulmonary disease — a progressive lung disease that to breathe
  • Emphysema — a type of COPD that includes lung damage that causes air to become trapped in your lungs and makes it harder to breathe

Hormonal Imbalance

Your hormones are chemical messengers of your body and control many functions. If your hormones are not in balance, it can make you feel tired and fatigued.

The most common example of a hormone problem that causes fatigue is hypothyroidism, a condition where your thyroid hormone levels are too low. Your thyroid hormone is responsible for controlling your body’s metabolism. When you don’t have enough thyroid hormone in your body, your metabolism slows down, causing you to feel fatigued.

Autoimmune Diseases

An autoimmune disease happens when your immune system mistakenly starts to attack your own body tissues.

Fatigue is a common and often debilitating symptom of several different autoimmune diseases. Researchers don’t fully understand why autoimmune diseases cause fatigue. It may be caused by increased inflammation that occurs when your immune system is activated.

Common autoimmune diseases that can cause fatigue include:

  • Rheumatoid arthritis
  • Psoriasis
  • Lupus
  • Type 1 diabetes
  • Multiple sclerosis (MS)


Almost everyone diagnosed with cancer experiences cancer-related fatigue. Fatigue can be a symptom of many different types of cancer because of the extra energy it takes for your body to fight cancer. Fatigue can also be a side effect of many different cancer treatments.

Other Chronic Conditions

Any medical condition that affects how your body uses energy or makes it difficult to sleep can cause fatigue.

Fatigue is a possible symptom of many different chronic (long-term) medical conditions, including:

3. Mental Health Conditions

Fatigue is a common symptom of mental health conditions such as depression, anxiety, and post-traumatic stress disorder (PTSD). Other symptoms of mental health conditions can contribute to feelings of fatigue, such as:

  • Apathy — a loss of interest in activities you enjoy
  • Changes in appetite — an increase or decrease in appetite that can cause changes in weight
  • Changes in sleep — sleeping too much or too little

Depression is common — about one in six people will experience depression at some point in their lives. If you experience a sad or depressed mood, thoughts of worthlessness, or thoughts of death or suicide, along with fatigue and other symptoms of depression, seek medical care right away.

4. Sleep Disorders

It’s no surprise that if you don’t get enough sleep, you will feel sleepy. Sleep is an important part of your physical and mental health. If you have a sleep disorder, it can make it difficult for you to get enough sleep.

Several sleep disorders can cause fatigue; three of the most common are discussed below.


Insomnia involves having trouble falling asleep, staying asleep, or waking up too early. It’s the most common sleep disorder — about one in three adults report symptoms of insomnia.

You may be more likely to experience insomnia if you have any of the following risk factors:

  • Family history of sleep disorders
  • People with active brain chemistry
  • People who are light sleepers
  • Acid reflux
  • Parkinson’s disease
  • Sleep hygiene
  • Alcohol use
  • People who have nightmare disorder

Sleep Apnea

Sleep apnea is a condition where your breathing stops and restarts while you sleep. If you stop breathing due to a blockage of your airway, it’s known as obstructive sleep apnea (OSA). If you stop breathing due to changes in brain signaling, it’s known as central apnea.

When you stop breathing in your sleep, your survival reflex kicks in to wake you up to start breathing again. Sleep apnea can prevent you from waking up feeling refreshed because your sleep cycle has been interrupted several times throughout the night to restart your breathing.

Sleep apnea is estimated to affect between 5% and 10% of the population.

Restless Legs Syndrome

Restless legs syndrome (RLS) is a neurological (brain) disorder that causes an irresistible urge to move your legs because of uncomfortable sensations. RLS is considered a sleep disorder because the symptoms are triggered when you try to rest and fall asleep. RLS can result in symptoms of fatigue due to lack of sleep.

As many as 10% of Americans experience symptoms of RLS.

5. Medications

Some prescription and over-the-counter (OTC) medications have side effects that can cause drowsiness or fatigue. Medications that can cause fatigue include:

  • Sedatives
  • Antipsychotics
  • Antidepressants
  • Opioid pain medications
  • Beta-blockers
  • Seizure medications
  • Chemotherapy
  • Antihistamines
  • Melantonin
  • Cough and cold medications

When Should You Worry About Fatigue?

Everyone may feel tired from time to time. If you feel tired all the time and nothing helps, you may need to talk to your doctor about what’s causing your fatigue.

Call your doctor if you experience any of the following:

  • You feel fatigued for several days
  • You find it difficult to complete your usual daily activities
  • You don’t know what’s causing fatigue
  • You became fatigued suddenly
  • You’re older than 65 years old

Fatigue may be a symptom of another condition if you experience fatigue with other symptoms, including:

  • Weight loss
  • Shortness of breath
  • Changes in how fast your heart beats
  • Headaches
  • Vision problems
  • Nausea and vomiting
  • Muscle weakness
  • Intrusive thoughts

If you’re experiencing persistent fatigue, it may be caused by a chronic condition. Keep in mind that sometimes fatigue has no known cause.

Coping With Fatigue

Causes of Fatigue

Talk to your doctor about the best way to manage fatigue symptoms, including medical treatments and medications. If fatigue is caused by a chronic condition, fatigue can improve with appropriate treatment for that condition.

A quick fix for fatigue isn’t always possible. Here are some tips for coping with fatigue:

  • Get plenty of exercise — I generally recommend 150 minutes of physical activity per week
  • Avoid napping for too long — if you must nap, limit it to 30 minutes early in the day
  • Go to sleep and wake up at the same time each day
  • Plan for at least seven hours of sleep every night
  • Find ways to manage your stress
  • Eat a balanced diet
  • Avoid smoking
  • Manage your chronic health conditions
  • Don't drink alcohol or caffeine or smoke tobacco late in the day
Articles authored by Dr. Connor are intended to facilitate awareness about health and wellness matters generally and are not a substitute for professional medical attention or advice from your own healthcare practitioner, which is dependent on your detailed personal medical condition and history. You should always speak with your own qualified healthcare practitioner about any information in any articles you may read here before choosing to act or not act upon such information.
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