Why is my teenager always tired?
Often because the teenage body clock moved later and the school bell did not. Here is what we know, what helps, and when tiredness deserves a visit.
Picture a 16-year-old who is wide awake at 11:30 p.m., impossible to rouse at 6:45 a.m., and asleep on the couch by 4. Her parents wonder if something is wrong. Usually, something is simply working as designed.
The short answer: most teenagers need about 8 to 10 hours of sleep, most get less, and a shift in the teenage body clock makes that gap easy to fall into. The clocks just went back, and a lot of households are noticing who is dragging.
What is happening in there
During adolescence, the body clock tends to drift later. Teens often do not feel sleepy until late evening, even when they are tired. Then early school start times cut the morning short. The American Academy of Sleep Medicine recommends 8 to 10 hours for ages 13 to 18, and has noted that many high school students get seven or fewer on school nights. Weekend sleeping-in is often the body paying back a debt.
Phones, homework, sports, and jobs pile onto that. I would not blame any one of them. It is rarely a character flaw, and it is not laziness.
Why it matters
Short sleep in teens is linked with trouble concentrating, low mood, and drowsy driving. I want to be careful here: these are associations, and sleep is tangled up with everything else in a teenager’s life, so we cannot say sleep alone causes each of them. But the pattern is consistent enough that I take it seriously, especially for a new driver.
What tends to help
- A steadier schedule. A wake time that does not swing by three hours on weekends helps the clock settle.
- Morning light, dimmer evenings. Light is the clock’s main signal.
- Screens out of the bedroom overnight. The research on screens and sleep is mixed about how much the light itself matters, but a buzzing phone at midnight clearly costs sleep.
- Caffeine earlier, or less. Afternoon energy drinks can quietly push bedtime back.
- Naps kept short and not too late in the day.
None of this is magic, and teens have a say in what they will actually do. A plan they helped write beats a rule they resent. Whether schools should start later is a community conversation. The AASM supports start times of 8:30 a.m. or later for middle and high school. California has set a floor in law (SB 328): high schools may not start before 8:30 a.m. and middle schools not before 8:00 a.m., with exceptions such as rural districts. If your teen’s school starts earlier, ask your district which rules apply.
When tiredness is more than sleep
Come in if your teen is sleeping enough but still exhausted, snores loudly or stops breathing at night, seems persistently sad or irritable, has lost interest in things they enjoyed, has changes in weight or appetite, or has dozed off while driving or in class. Tiredness can also come from anemia, thyroid problems, depression, or other causes, and those are worth sorting out. This is also a good moment for some private time with the doctor, where teens can say what they would not say in front of a parent.
If you want to know how I think about care for this age group, see my page on teen and adolescent primary care, or my note on caring for a whole family. I see teens and their parents here in Noe Valley.
What we do not know: exactly how much any individual teen needs, and how much of the sleep loss is biology versus habit. The ranges are good guides, not prescriptions.
If you would like to talk about your teenager, send me a note.
Sources: American Academy of Sleep Medicine, position statement on delaying middle and high school start times (J Clin Sleep Med); Paruthi S, et al., Recommended amount of sleep for pediatric populations: AASM consensus statement (J Clin Sleep Med, 2016); California SB 328 (2019), Education Code section 46148.
This article is general educational information, not individual medical advice. What is appropriate for you depends on your history and circumstances.