What Causes Fatigue?

Conditions list medically reviewed by George Krucik, MD, MBA

Fatigue is a term used to describe an overall feeling of tiredness or lack of energy. It isn’t the same as simply feeling drowsy or sleepy. When you’re fatigued, you have no motivation and no energy. Being sleepy may be a symptom of fatigue, but... Read More

Fatigue is a term used to describe an overall feeling of tiredness or lack of energy. It isn’t the same as simply feeling drowsy or sleepy. When you’re fatigued, you have no motivation and no energy. Being sleepy may be a symptom of fatigue, but it’s not the same thing.

Fatigue is a common symptom of many medical conditions, which range in severity from mild to serious. It’s also a natural result of some lifestyle choices, such as lack of exercise or poor diet.

If your fatigue doesn’t resolve with proper rest and nutrition, or you suspect it’s caused by an underlying physical or mental health condition, see your doctor. They can help diagnose the cause of your fatigue and work with you to treat it.

What causes fatigue?

There are many potential causes of fatigue. They can be divided into three general categories:

  • lifestyle factors
  • physical health conditions
  • mental health issues

Lifestyle factors

If you’re experiencing fatigue, your activities and other lifestyle choices may be the root cause. For example, fatigue can result from:

  • physical exertion
  • lack of physical activity
  • lack of sleep
  • being overweight or obese
  • periods of emotional stress
  • boredom
  • grief
  • taking certain medications, such as antidepressants or sedatives
  • using alcohol on a regular basis
  • using street drugs, such as cocaine
  • consuming too much caffeine
  • not eating a nutritious diet

Physical health conditions

Many medical conditions can also cause fatigue. Examples include:

  • anemia
  • arthritis
  • fibromyalgia
  • chronic fatigue syndrome
  • infections, such as cold and flu
  • Addison’s disease, a disorder that can affect your hormone levels
  • hypothyroidism, or underactive thyroid
  • hyperthyroidism, or overactive thyroid
  • sleep disorders, such as insomnia
  • eating disorders, such as anorexia
  • autoimmune disorders
  • congestive heart failure
  • cancer
  • diabetes
  • kidney disease
  • liver disease
  • chronic obstructive pulmonary disease
  • emphysema

Mental health issues

Mental health conditions can also lead to fatigue. For example, fatigue is a common symptom of anxiety, depression, and seasonal affective disorder.

When is it time to see your doctor?

You should make an appointment with your doctor if you’re feeling fatigued and you:

  • can’t think of anything that might account for your fatigue
  • have a higher-than-normal body temperature
  • have experienced unexplained weight loss
  • feel very sensitive to colder temperatures
  • regularly have trouble falling or staying asleep
  • believe you may be depressed

If you’ve made efforts to address the most common lifestyle causes, such as lack of rest, poor eating habits, and stress, without success, and your fatigue has continued for two weeks or more, make an appoint with your doctor.

In some cases, your fatigue might be caused by a serious medical condition. Go to the hospital immediately if you experience fatigue along with any of the following symptoms:

  • rectal bleeding
  • vomiting blood
  • severe headache
  • pain in your chest area
  • feelings of faintness
  • irregular heart beat
  • shortness of breath
  • severe pain in your abdominal, back, or pelvic region
  • thoughts of suicide or self-harm
  • thoughts of harming another person

How will your doctor treat fatigue?

Your doctor’s recommended treatment plan will depend on the cause of your fatigue. To develop a diagnosis, they will likely ask you a number of questions about:

  • the nature of your fatigue, including when it started and whether it gets better or worse at certain times
  • other symptoms that you’ve been experiencing
  • other medical conditions that you have
  • your lifestyle and sources of stress
  • medications that you’re taking

If your doctor suspects you have an underlying medical condition that’s causing your fatigue, they may order one or more tests. For example, they may order blood or urine tests.

What are some lifestyle changes that can help reduce fatigue?

A number of measures can help lessen fatigue caused by a less-than-ideal lifestyle. To help boost your energy levels and overall health:

  • drink enough fluids to stay hydrated
  • practice healthy eating habits
  • exercise on a regular basis
  • get enough sleep
  • avoid known stressors
  • avoid a work or social schedule that’s overly demanding
  • take part in relaxing activities, such as yoga
  • abstain from alcohol, tobacco, and other recreational drugs

These lifestyle changes may help ease your fatigue. It’s also important to follow your doctor’s recommended treatment plan for any diagnosed health conditions. If left untreated, fatigue can take a toll on your physical and emotional well-being. 

Medically reviewed by Elaine K. Luo, MD on October 18, 2016Written by Krista O'Connell


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This feature is for informational purposes only and should not be used to diagnose. Please consult a healthcare professional if you have health concerns.

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