Symptoms, Causes, Related Conditions, Questions & Related Topics

Top 5 Causes of Fatigue

1. Stress

Stress is one of the most common causes of fatigue, especially if a person feels tired after getting a full night’s sleep.[1] One of the reasons for this is that stress often doesn’t let us sleep as well as we would like; instead of sleeping well, we toss and turn, making us feel fatigued in the morning. Heavy stress can make you feel tired and weak all the time. If it goes on for too long, you might require medical help.

2. Not Sleeping

Whether you choose not to sleep because you need to stay up and write a paper, because you want to hang out with friends, or because you use your sleep time for some other reason, you will feel fatigued the next day.[2] Most people only make this choice occasionally, and those who do it too often can make themselves extremely tired and even ill. Those who try to sleep and can’t could be experiencing another problem entirely — one that requires diagnosis and treatment.

3. Use of Medicine, Drugs, or Caffeine

Some people become fatigued as a side effect of using an external substance. Many medications list fatigue as a possible side effect, but over time, your body should stop experiencing the issue as acutely. If it doesn’t, you may want to ask your doctor to switch your medication. In addition, people who drink or use drugs too often can also experience intense side effects of fatigue, especially when they come down from their high. Even caffeine, which is a fairly moderate substance, can cause withdrawal and lead to drowsiness, and too much caffeine can also make a person feel fatigued.[3]

4. Grief or Sadness

Many people who experience temporary bouts of sadness or grief find themselves feeling fatigued, either because they cannot sleep or because they just feel weary under the weight of their sadness.[4] This can occur when you go through a breakup, get fired, or lose a loved one, but over time, you begin to feel like yourself again. Long-term grief or sadness accompanied by fatigue usually requires more help, often from a medical professional.

5. Sedentary Lifestyle

You can experience fatigue as the result of an extremely sedentary lifestyle. Even people who don’t use drugs or caffeine can sometimes resist the need to exercise or eat right, leading them to feel sluggish and have low energy.[4] If you feel fatigued, it’s a good idea to think about your day-to-day actions and what you could do to feel more energized.

Possible Health Conditions Related to Fatigue

1. Mental Disorders

Many mental disorders, including depression, bipolar disorder, an eating disorder, or an anxiety disorder, cause people to experience fatigue.[5] Mental health is important, and you should not feel ashamed of any mental health issues. If you notice feelings of loneliness, isolation, fatigue, hopelessness, anxiety, or depression that do not go away, seeking help is crucial.

2. Anemia

Anemia occurs when a person’s blood cannot bring enough oxygen to the rest of the body. It can be the result of many different conditions, including pregnancy, ulcers, heavy menstruation, polyps, colon cancer, and others. When your blood does not have enough oxygen, you can feel dizzy and fatigued as well as cold.[6] It’s important to be diagnosed with anemia so your doctor can find the underlying cause.

3. Diabetes

Fatigue is one of the most common symptoms of diabetes, a disease in which your body cannot control the levels of sugar in your blood. Other symptoms are hunger; infections in the bladder, kidneys, and skin that do not heal as quickly as they should; and frequent urination.[7] It’s important to let your doctor check you for diabetes, especially if you experience long-term fatigue and have a family history of the disease.

4. Chronic Fatigue Syndrome (CFS)

CFS, or chronic fatigue syndrome, is an illness that causes a person to experience intense fatigue (often for days on end), trouble sleeping, dizziness, pain or discomfort, and post-exertional malaise — when symptoms worsen after physical activity.[8] Although the cause of CFS is unknown, symptoms can be managed with the help of strategies your doctor can teach you as well as self-care techniques that can help you sleep better and manage stress.

5. Cancer

Cancer can often cause fatigue as one of its symptoms, but there are many different types of cancer. As such, it is hard to determine whether a person has it based on a single symptom. Usually, other symptoms in addition to fatigue plague an individual struggling with cancer. A syndrome called cancer-related fatigue causes long-term fatigue, distress, a decreased desire to take care of yourself, and an inability to concentrate.[9] Someone who has cancer should be monitored for these symptoms, especially while going through treatment.

Questions Your Doctor May Ask About Your Fatigue

  • How long have you dealt with fatigue?
  • Do you experience any additional symptoms?
  • Do you feel sad, depressed, anxious, or stressed in addition to feeling fatigued?
  • How much sleep do you get? Do you sleep well? What are your sleep habits?
  • What is your day-to-day lifestyle like?

Fatigue May Also Be Known as

  • Tiredness
  • Exhaustion
  • Weakness


  1. National Library of Medicine. Fatigue. https://medlineplus.gov/fatigue.html
  2. HealthLine. Fatigue. https://www.healthline.com/symptom/fatigue
  3. National Library of Medicine. Caffeine in the diet. https://medlineplus.gov/ency/article/002445.htm
  4. Victoria State Government. Fatigue. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/fatigue
  5. National Library of Medicine. Mental disorders. https://medlineplus.gov/mentaldisorders.html
  6. National Library of Medicine. Anemia. https://medlineplus.gov/anemia.html
  7. National Library of Medicine. Type 2 Diabetes. https://medlineplus.gov/ency/article/000313.htm
  8. National Library of Medicine. Chronic Fatigue Syndrome. https://medlineplus.gov/chronicfatiguesyndrome.html
  9. American Cancer Society. Cancer-related fatigue. https://www.cancer.org/treatment/treatments-and-side-effects/physical-side-effects/fatigue/what-is-cancer-related-fatigue.html

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