Some things to consider that will help answer your question include whether you have noticed that your son has had any problems from an academic standpoint from his lack of sleep? Does he drink a lot of caffeine or caffeinated beverages throughout the day? Does he have trouble sleeping at night or is he choosing to do other things instead of sleep? Does he have difficulty with his memory or increased fatigue throughout the day? These are important things to consider and discuss with your child's pediatrician
as he or she will be able to take this information, along with his medical history, presenting symptoms, and clinical exam and decide upon the appropriate work up. This may include lab tests, imaging studies, or perhaps a referral to a specialist.
It is very important that children sleep the appropriate amount of time per day as this helps them in the long term with mental and physical development. Your child may be going through a phase, and this may be normal for him at this time, but because there are other potentially concerning causes for this, it is important that you are evaluated by a medical professional such as his pediatrician.