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What is chronic fatigue?

Fatigue is a common among teens. Sometimes, your teen may have fatigue for months or even years and may develop symptoms of "chronic fatigue syndrome."

There are several common causes of fatigue in teens.


Mononucleosis ("mono," or "the kissing disease"): Mononucleosis is one of the most common causes of extreme tiredness in teens. Some of the other signs of mono include:

Mono usually is diagnosed by a blood test called the "mono spot." The best treatment for mono is getting plenty of rest and eating a healthful diet. Most people get better within a month. If your teen has mono, he should not play any contact sports such as soccer, football, or lacrosse during the month after he gets mono to lessen the chance of a ruptured spleen.


Anemia is the state of not having enough red blood cells, and it is a common cause of tiredness in teens, especially girls. The most common causes are not enough iron in the diet or, for girls, losing iron due to heavy menstrual periods. With anemia, your child may feel weak and more tired than usual and not do as well at school or in sports. He may also appear pale. Anemia needs to be diagnosed by a complete blood count (called a CBC). To prevent iron deficiency anemia, your teen should be getting enough iron from his diet and/or taking a multivitamin with iron. If iron deficiency anemia is diagnosed, he will need additional iron.

Low thyroid

Low thyroid is another cause of feeling fatigued, but it is not terribly common. A blood test can help make the diagnosis.

Erratic or changing sleep patterns

Another common cause of fatigue is simply not getting enough sleep. Your teen may have lots of homework that keeps them up late during the week, and/or have to wake up early. On weekends they may go to bed even later and then not feel like getting up until noon on Saturday and Sunday.

These changes in sleep pattern, coupled with stress during the week, can lead to fatigue.


Depression (feeling sad or "blue") is another common causes of fatigue in teens. If your teen continues to feel sad and can't enjoy friends, family and new challenges, he should be seen by a health care provider or mental health clinician.

If your child is fatigued, it's a good idea for him to get a medical evaluation to check for any specific cause and determine appropriate treatment.

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