THIS USER ASKED ๐Ÿ‘‡

Umberto was referred to a/an who specializes in diagnosing and treating blood disorders.

THIS IS THE BEST ANSWER ๐Ÿ‘‡

Umberto was referred to HEMATOLOGIST which specializes in the diagnosis and treatment of blood disorders.
A haematologist is a medical doctor who uses his or her knowledge of blood to diagnose and treat people with blood conditions. Hematology involves the study of the blood, how the blood forms, the organs that form blood and the medical conditions associated with blood diseases.