My friend's eyes get tired easily and his blood sugar is high. who should he see?

A diabetic Dr.: This sounds like a form of diabetes. Depending on your age and clinical history, it could be type i or ii, with type ii devewloping in older people. A good internal medicine dr. Or an endocrinologist dr. Would be a great start in ascertaining what this could be, through history and clinical tests.

Establish a Home: He needs a primary care physician, like a specialist in family medicine or internal medicine. Elevated blood sugars can mean diabetes, but there are other disease processes that need to be ruled out, as well. The added benefit to seeing primary care is the ability to establish a "medical home" where his care can be coordinated with any specialists he may need.