What Does Fatigue Feel Like?

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Fatigue can have a major impact on enjoying daily activities—or even just trying to function normally. Knowing what constitutes actual fatigue as a potentially concerning symptom vs just feeling sleepy is important to know. Amanda Robinson, ARNP for UnityPoint Health, explains what fatigue typically feels like and when it’s time to see a doctor.

What Does Fatigue Feel Like?

The term fatigue describes being extremely tired, sleepy, exhausted or having a general lack of energy. 

“Being fatigued not only is a physical feeling, it can also be a mental feeling, too,” Robinson says. “If you can’t do the tasks or activities you’re normally capable of doing, or fall asleep at unexpected times of the day, you might be experiencing fatigue,” Robinson says.

How long fatigue lasts varies from person to person.

What’s the Difference: Fatigue, Tiredness and Lethargy 

Fatigue vs. Being Tired 

Fatigue is more persistent, constant and lingering compared to feeling tired. Feeling fatigue usually interrupts your day-to-day activities and isn't always relieved by sleeping more.

“Sometimes the differences between fatigue and being tired can be difficult for people to differentiate. Many say they always feel tired. Fatigue is usually found to be more than the everyday tired, which occurs after a long day of work, school or taking care of family,” Robinson says.

Fatigue vs. Lethargy 

Lethargy and fatigue often go hand-in-hand, but lethargy generally refers to a low amount of energy. Usually when you’re feeling tired or fatigued, you also feel a lack of energy, or lethargy.

What Causes Fatigue? 

“There are so many causes for fatigue. In fact, it’s been found that about a third of people with fatigue never find the reason. Some of the causes are treatable and some are not,” Robinsons says.

13 Causes of Fatigue

  • Missing nutrients. Feel fatigued may be due to missing vitamins and minerals in your diet, such as being low on vitamin D, iron, magnesium, potassium, vitamin B12 or folic acid.
  • Poor sleep hygiene. Sleep hygiene is the routine you have leading up to sleep. Good sleep hygiene would include a comfortable bedroom, no distractions and a cool environment.
  • Anxiety. Whether you’re feeling anxious, or you’ve been diagnosed with anxiety as a mental health condition, one of the main symptoms is fatigue.
  • Depression. Most who experience depression will notice fatigue or tiredness.
  • Anemia. This is when the body doesn’t have enough healthy red blood cells, resulting in reduced oxygen flow to organs. In turn, your body must work harder, and that’ll make you feel tired.
  • Sleep Disorders. People with a sleep disorder, such as narcolepsy or sleep apnea, will notice fatigue.
  • Thyroid disease. Those with a thyroid disease don’t have the right balance of hormones. Whether an overactive thyroid or an underactive one, both leave you feeling fatigue.
  • Diabetes. People with diabetes struggle with insulin creation or use. Cells need insulin to absorb glucose from the blood to create energy. Fatigue happens when the cells don’t get enough glucose.
  • Heart Disease. If your heart isn’t working correctly, you’ll feel fatigued.
  • Lung disease (like COPD). Reduced oxygen flow will result in fatigue.
  • Medication. Fatigue can be a side effect of medication.
  • Autoimmune disorders. Inflammation is often associated with feelings of fatigue.
  • Colds, flu, COVID-19. When you’re ill, your body uses a lot of energy to compensate and get over the illness.

“Typically, when the body is fatigued, it’s because it’s working to care for the underlying problem or trying to heal from an illness,” Robinsons says.

What is Chronic Fatigue?

Chronic fatigue syndrome is a condition occurring primarily in women. The cause is unknown. 

Research suggests it can be from environmental or genetic issues/factors. Generally, the fatigue lasts for more than six months. If you have this condition, your fatigue gets worse with physical and mental activity and doesn’t improve with rest.

What is Adrenal Fatigue?

You may have read or heard about adrenal fatigue, but Robinson says it’s not a real diagnosis. However, adrenalin insufficiency is an actual diagnosis.

“Your adrenal gland produces many different hormones important for life. When something goes wrong with the adrenal gland, this is known as adrenal insufficiency. One of the symptoms is fatigue. There are other symptoms as well, such as body aches, weight loss, low blood pressure, loss of hair and skin discoloration,” Robinson says. 

How to Treat Fatigue at Home

Start by looking at what you’re putting in your body. You might simply need a daily vitamin.

“A good sleep hygiene is especially important. It’s recommended to limit caffeine and alcoholic beverages close to bedtime. Also, reduce stimulant activities and electronics before bed. Our mind needs time to wind down after a long day to be able to relax and rest well,” Robinson says.

Another idea from Robinson — a sleep diary. Each day, write down foods, drinks and medication and how it impacts your sleep. You might be able to identify themes or possible factors that are impacting your sleep.

When to See a Doctor

If you feel like fatigue prevents you from doing daily functions and is negatively impacting your life, it’s time to see your doctor or visit urgent care. Usually, providers begin with basic testing with may warrant further investigation. 

“So many people suffer from fatigue. No one is alone for feeling this way. The best thing is to recognize it and make an appointment with a healthcare provider to talk about your concerns. The sooner you get evaluated, hopefully, the sooner it can be resolved,” Robinson says.

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