Hematology is the study of the blood and blood disorders in the body. A hematologist is a physician who has expertise in diseases of the blood and bone marrow, and treats vascular and clotting problems. The hematologist also treats blood disorders such as hemophilia, leukemia, lymphoma, anemia and sickle cell disease.

Physicians in this specialty treat patients suffering from numerous diseases and illnesses, but some of the most common are Malaria, lymphoma, Non-Hodgkin's Lymphoma, Myelomas, Evans' syndrome, AIDS, Leukemia, hemophilia, Thrombocytopenia, Sickle-cell disease, Myeloma, Pernicious anemia, Hodgkin's disease, Thalassemia, Myelofibrosis, Infectious mononucleosis, Agranulocytosis, Systemic lupus erythematosus (SLE), Megaloblastic anemia, and Autoimmune hemolytic anemia.

Once properly diagnosed, practitioners can perform numerous procedures on patients including Chemotherapy, Bone marrow transplant, blood transfusion, radiotherapy, Intramuscular injections, Anticoagulation therapy, and Venesection.

To diagnose patients with possible illnesses and diseases, specialists will often perform one of many tests including Coombs test, D-dimer, Prothrombin time, Bone marrow biopsy, Protein electrophoresis, serum Ferritin level, Partial thromboplastin time, Vitamin B12 and Folate levels, Erythrocyte sedimentation rate (ESR), Blood film, Full blood count, and Hemoglobin electrophoresis.

Doctor density varies by specialty and location. Illinois has 580 practicing hematologists. Broken out by city, hematology doctor density in Alton is 5, in Arlington Heights is 10, in Aurora is 9, in Belleville is 7, in Benton is 1, in Berwyn is 12, in Bloomington is 2, in Blue Island is 3, in Breese is 2, in Burbank is 2, in Burr Ridge is 26, in Carbondale is 2, in Carlinville is 2, in Centralia is 6, in Champaign is 3, in Chester is 3, in Chicago is 238, in Chicago Heights is 3, in Clinton is 2, in Crystal Lake is 1, in Danville is 1, in Darien is 5, in Decatur is 14, in Deerfield is 1, in Dekalb is 2, in Des Plaines is 1, in Edwardsville is 1, in Effingham is 5, in Eldorado is 1, in Elgin is 9, in Elmhurst is 12, in Eureka is 2, in Evanston is 18, in Freeport is 5, in Galesburg is 1, in Geneseo is 1, in Geneva is 6, in Glendale Heights is 1, in Granite City is 3, in Harrisburg is 1, in Harvey is 6, in Havana is 1, in Herrin is 2, in Highland is 1, in Highland Park is 8, in Jacksonville is 5, in Joliet is 20, in Kankakee is 4, in Lake Forest is 6, in Lansing is 1, in Libertyville is 3, in Lincoln is 1, in Litchfield is 1, in Lockport is 3, in Loves Park is 1, in Mahomet is 2, in Marion is 3, in Martinsville is 2, in Mattoon is 4, in Mchenry is 11, in Metropolis is 1, in Midlothian is 1, in Moline is 5, in Morris is 7, in Mount Vernon is 3, in Naperville is 18, in Normal is 6, in North Chicago is 3, in Northbrook is 1, in Oak Forest is 1, in Olney is 1, in Ottawa is 1, in Palos Heights is 8, in Pana is 1, in Paris is 1, in Park Ridge is 14, in Peoria is 17, in Pinckneyville is 1, in Pittsfield is 1, in Quincy is 5, in Red Bud is 1, in Rock Island is 1, in Rockford is 9, in Rolling Meadows is 13, in Salem is 1, in Sandwich is 4, in Silvis is 7, in Sparta is 5, in Springfield is 22, in Sterling is 2, in Streator is 1, in Taylorville is 7, in Urbana is 8, in Vandalia is 2, in Vernon Hills is 3, in Warrenville is 1, in Waukegan is 2, in Wheaton is 3, in Woodstock is 3, and in Yorkville is 6.

Most people think that Chicago, because of its size and popularity, is Illinois’ capital city, but that distinction belongs to Springfield, home of the Abraham Lincoln Museum. Illinois has hundreds of museums, numerous yearly art and ethnic festivals, a lakeshore bordering Lake Michigan, and the many national forests and parks that offers visitors camping, horseback riding, biking, kayaking, and fishing. Chicago is home to the Sears Tower, the Shedd Aquarium, the Art Institute of Chicago, the Adler Planetarium, the Museum of Science and Industry, and other cultural opportunities and restaurants in the Navy Pier area.

According to 2005 Census estimates, Illinois has a population of 12,763,371. Of this population, 3,172,677 are under the age of 18 and 1,523,937 are at or above the age of 65.