Is 4-5 hours enough sleep for a 16 year old
When do you get tired? If you feel wide awake at 6 am, but you're already sleepy by dinner time, then maybe you just need to shift your sleep cycle back a bit. But if you really just don't get tired until late at night, and wake up naturally early in the morning, then you're probably fine.
How much do you sleep during school breaks? Like over the summer, when you can sleep as much as you want, do you still only sleep 4-5 hours, or do you sleep more? If you're sleeping that little when there's no pressure to do more in a single day, then it's more likely that it's just your natural sleep cycle. But if you sleep 10 hours a night during summer break, then it's probably that you're stressed out during school, in which case it's something that needs to be addressed.
There are various neurological disorders that can cause insomnia, so if you can't figure out why you sleep so little, I'd recommend getting a second opinion. There are sleep specialists who can look at the EEG pattern when you sleep to determine if there's anything abnormal in your sleep pattern besides that it's so short, and a few other tests to see if there's any pathology there. It may turn out that you just need abnormally little sleep, but it is worth getting a second opinion in case there is something else going on.
Learn How You Can Create Energizing Sleep And Cure Insomnia Naturally. Anyone Can Double Their Energy Levels And Naturally Transform Their Body Into A Restful Sleep Magnet