Causes of Fatigue: 6 Conditions You Need to KnowChronic Conditions

Causes of Fatigue: 6 Conditions You Need To Know

Do you always feel tired? Do you often have difficulty getting through the day because of lack of energy? Sometimes, being tired is expected and normal (such as after an all-nighter, a bout of the flu, or a busy non-stop week). However, if you find yourself always feeling fatigued and worn out despite adequate rest, to the point your tiredness negatively affects your quality of life, it’s time to do something about it.

In this article, I will discuss six causes of fatigue and daytime sleepiness that—while common and treatable—often goes undiagnosed. In another article, I discuss practical ways in which you can fight fatigue and improve your energy level. 

The Many Causes of Fatigue

Many medical conditions, unsurprisingly, can cause you to feel tired. To give you an idea, the following is a non-comprehensive list of conditions that can lead to chronic fatigue:

COVID-19 infection
Thyroid problems
Mylagic Encephalomeylitis
(Chronic fatigue syndrome)
Addison’s disease
Eating disorders
Autoimmune disorders
Heart diseases
Chronic obstructive pulmonary disease
Kidney disease
Liver disease

For this article, I have selected six common conditions that I feel are important for everyone to be aware of, especially if you do suffer from chronic fatigue. If you do think that you might have one or more of these conditions, I encourage you to have a honest discussion with your health care professional and to get a check up.

6 Common Causes of Fatigue


Causes of Fatigue You Need to Know

Affecting millions of people worldwide, anemia is one of the most common blood conditions.

It is a condition in which you don’t have enough red blood cells—either because you are losing blood (such as with heavy periods or stomach ulcers) or your body is not making enough (such as in the case of iron, folic acid, or vitamin B12 deficiency).

Especially for women in their childbearing years, anemia is a common hidden cause of fatigue.

Furthermore, those who take nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and aspirin are at higher risk for stomach irritation and ulcers that can also lead to anemia.

If you think any of the characteristics listed below applies to you, I encourage you to talk to your doctor.

Ask your doctor about anemia if:

  • You have heavy menstrual cycles or periods that last over a week
  • You have uterine fibroids or polyps
  • You take NSAIDs frequently (pain medications such as ibuprofen, aspirin, and naproxen)
  • You find yourself craving the taste of dirt, clay, ice, or other non-nutrient substances (this is a condition called “pica” that often results from vitamin deficiency)

Seasonal Allergies

Causes of Fatigue You Need to Know allergies

Seasonal allergies, or allergic rhinitis, is one of the most common unsuspecting causes of chronic fatigue. Allergies can be triggered by pollen, dust mites, cockroaches, animal dander, molds and mildew, or even weather changes.

A simple evaluation by a health care professional can determine whether you indeed have allergies as well as work with you to find the best solutions.

If you do have allergies, the good news is that most cases are easily manageable with over-the-counter medications and some environmental precautions.

Ask your doctor about seasonal allergies if you frequently experience:

  • Itchy or watery eyes 
  • Itchiness in general
  • Headache
  • Sneezing or coughing
  • Nasal congestion, runny nose, or post-nasal drip
  • Wheezing or tendency to breathe through the mouth

Depression or Anxiety

Both depression and anxiety are common causes of chronic fatigue that can keep you feeling tired even when you get enough sleep. While depression can be caused by many things, it can seem to come out of the blue after a pregnancy (postpartum depression) and can also hit unsuspecting people in the wintertime (seasonal affective disorder, or SAD).

causes of fatigue depression anxiety

Ask your doctor about depression if you frequently experience:

  • Feelings of sadness, tearfulness, emptiness or hopelessness
  • Angry outbursts, irritability or frustration, even over small matters
  • Loss of interest or pleasure in most or all normal activities, such as sex, hobbies or sports
  • Sleep disturbances, including insomnia or sleeping too much
  • Tiredness and lack of energy, so even small tasks take extra effort
  • Reduced appetite and weight loss or increased cravings for food and weight gain
  • Anxiety, agitation or restlessness
  • Slowed thinking, speaking or body movements
  • Feelings of worthlessness or guilt, fixating on past failures or self-blame
  • Trouble thinking, concentrating, making decisions and remembering things
  • Frequent or recurrent thoughts of death, suicidal thoughts, suicide attempts or suicide

While this article will not go into further details on mental health, if you feel like you may be depressed (or are just feeling really sad), please talk to someone you know or do it anonymously and confidentially through the free National Suicide Prevention Hotline:

National Suicide Prevention Hotline
1-800-273-TALK (8255)

Underactive Thyroid (Hypothyroidism)

Causes of Fatigue You Need to Know hypothyroid

The thyroid is a small, butterfly-shaped gland located at the front base of your neck. It helps set your metabolism (the rate at which your body uses energy).

When you have an underactive thyroid, your metabolism slows down. This not only causes you to feel tired, but it can lead to many other symptoms and changes in your body.

Incidentally, fatigue can also result from the opposite condition—hyperthyroidism—where you have too much thyroid. Fortunately, this condition is easy to test for with a simple blood test, so if you are experiencing the symptoms below, talk to your doctor about it. 

Ask your doctor about underactive thyroid if you experience:

  • Feeling cold frequently or cannot tolerate the cold
  • Unexplained weight gain
  • Frequent constipation
  • Extremely heavy menstrual cycles
  • Thinning hair
  • Dry skin
  • Joint pain, stiffness, or swelling
  • Muscle weakness
  • Puffiness in the face

Obstructive Sleep Apnea (OSA) 

Causes of Fatigue You Need to Know sleep apnea

Obstructive sleep apnea is a condition that occurs when your airway become partially (and sometimes completely) blocked when you are sleeping, preventing you from getting enough air into your lungs.

This results in low oxygen levels in the blood which end up affecting your health in many ways—one of which is chronic fatigue. When sleep apnea is left untreated, it can actually increase your risk of a stroke or heart attack. To learn more about OSA, please visit this article.

Talk to your health care professional if any of the below characteristics apply to you or if you suspect you might have sleep apnea. If your doctor also thinks you might have this condition, he or she will conduct a sleep study to help diagnose it. 

Ask your doctor about OSA if you frequently experience:

  • Loud snoring
  • Episodes in which you stop breathing during sleep — which would be reported by another person
  • Gasping for air during sleep
  • Awakening with a dry mouth
  • Morning headache
  • Difficulty staying asleep (insomnia)
  • Excessive daytime sleepiness (hypersomnia)
  • Difficulty paying attention while awake
  • Irritability



Fibromyalgia is a common cause of chronic fatigue and musculoskeletal pain, and it tends to affect women more than men. People with fibromyalgia often feel that no matter how long they sleep, they never feel rested, and as a result always feel tired during the daytime. Sometimes the fatigue can get so severe that it significantly gets in the way of their living a normal life.

Some people with fibromyalgia walk around with a constant hazy, mental feeling that makes it difficult to even concentrate; this is often called the ‘fibro fog.’ There are ways to manage the symptoms of fibromyalgia, but the first step, if you suspect that you may have it, is to get evaluated by a health care professional.

Ask your doctor about fibromyalgia if you frequently experience:

  • Deep muscle pain
  • Unexplained pain in many parts of the body
  • Painful tender points
  • Morning stiffness
  • Sleep problems
  • Painful menstrual cramps
  • Numbness and tingling in hands, arms, feet, and legs
  • Symptoms of anxiety or depression 

Now that you know some of the important causes of fatigue, check out this article to learn ways in which you can fight and improve your fatigue and tiredness. 

Phoebe Chi, MD
Phoebe Chi, MD

As a physician educator and the managing editor of Health + Inspiration, Dr. Chi aims to inform, empower, and inspire the reader community. She is the author of Being Empowered for a Healthy Heart: A personal guide to taking control of your health while living with chronic conditions, a poetry-infused health guide, and founder of Pendants for a Cause, a nonprofit organization with the purpose of raising funds to fight illness, provide care, and bring awareness to medically vulnerable populations around the world.

Pendants for a Cause Charity Jewelry

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