It isn’t normal for teens to feel tired all the time. While fatigue is often attributed to lifestyle factors, doctors usually first rule out physical and mental health conditions as the cause of a teen’s sleepiness and fatigue. Low thyroid, autoimmune disease, anemia and sleep disorders are common causes of weariness and lack of energy in teens, according to Boston Children’s Hospital.
Hypothyroidism -- caused by an underactive thyroid -- can make a teen feel fatigued and depressed. According to KidsHealth, while the symptoms of low thyroid function can come on slowly, a teen might begin to experience more problems if the condition goes untreated. While teens suffer many of the same symptoms of thyroid disease as adults do, additional symptoms often include muscle weakness, slow growth, impaired mental development and irregular menstrual periods in girls.
The National Institute on Alcohol Abuse and Alcoholism points out that because their brains are still developing, alcohol affects teens differently than it does adults. Besides the risk of developing an alcohol abuse problem, alcohol slows reaction time, impairs coordination and affects judgment. A lack of energy, poor concentration, irritability and problems in school are just some of the signs that your teen might be drinking alcohol.
A loss of energy and feeling tired and weak are common symptoms of anemia -- a condition that occurs when not enough red blood cells exist to carry oxygen to the rest of the body. According to WebMD, doctors often recommend iron supplements for teenage girls who aren’t getting all the iron they need through diet. The blood loss from heavy menstrual periods can cause iron deficiency and low iron can lead to feeling listless and lethargic.
The National Sleep Foundation reports that although teens generally need at least nine hours of sleep each night, most don’t get enough. Besides making a teen feel tired and drowsy, not getting adequate quality sleep can weaken the immune system, lead to mood swings and aggressive behavior, interfere with the ability to learn or increase cravings for unhealthful foods. Although many teens suffer from sleep disorders such as insomnia, sleep apnea or narcolepsy, these conditions can be treated.