16 year old boy is growing bald. What can be done? Should I consult a doctor? At 16 are medicines like Rogain safe? (Photo)

It is absolutely important to consult a doctor who can provide a formal diagnosis and determine if the hair loss is also caused by other factors like fungal or bacterial inflammation, stress etc. All drugs have the potential to incur side effects. And the physician can provide insight on your son’s likelihood to experience these. It is also possible to consider a hair transplant for young men by determining if a patient will reach severe baldness and therefore require a body hair transplant to provide enough grafts for the long term. Our clinic’s Shave Test and ability to extract body hair allows younger patients to benefit from these surgeries. You can find more information on how young patients can qualify for such a procedure in the link below. 

Absolutely, consult a physician. An "up close" examination of your son's scalp is essential along with a careful history and blood tests

At 16, it is difficult to make a diagnosis.  Seeing an expert is a good idea if you are concerned about this as a real problem now. 

Yes, should definitely have him seen by a hair loss specialist, in order to determine the cause of his hair loss and then be able to recommend appropriate treatment.  Many different causes of loss, and a detailed history and examination of his scalp would be needed.
Good luck!