Can a person with Type 1 Diabetes get a medical and learn to fly? A friend of mine has had Type 1 diabetes most of his life, and has it well under control.  How does he go about finding out if he can get his medical and learn to fly?
As far as the FAA is concerned your friend can get a medical, but he will need a special issuance medical, will only qualify for a third-class medical, and will be prohibited from operating aircraft outside the United States.
In addition there are some specific requirements to obtain the special-issuance medical for insulin-dependent diabetics, and monitoring requirements before and during flight which must be adhered to.

The FAA has a page of guidance for Aviation Medical Examiners that deals with insulin-dependent diabetes which your friend should review (and be prepared to discuss with their AME).
Diabetes.org also has a page on Diabetes and FAA Certification, and AOPA's medical folks would be a useful resource to help ensure that the special issuance medical goes through without any hiccups.