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:

Anemia
Allergies
Depression/anxiety
COVID-19 infection
Thyroid problems
Fibromyalgia
Mylagic Encephalomeylitis
(Chronic fatigue syndrome)
Infections
Addison’s disease
Arthritis
Eating disorders
Autoimmune disorders
Heart diseases
Chronic obstructive pulmonary disease
Cancer
Diabetes
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

Anemia

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.

Seasonal 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.

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).

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)

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. 

Obstructive Sleep Apnea (OSA) 

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. 

Fibromyalgia

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.

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. 

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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.