Diagnosis

Your doctor can usually diagnose measles based on the disease's characteristic rash as well as a small, bluish-white spot on a bright red background — Koplik's spot — on the inside lining of the cheek. However, many doctors have never seen measles, and the rash can be confused with a number of other illnesses. If necessary, a blood test can confirm whether the rash is truly measles. The measles virus can also be confirmed with a test that generally uses a throat swab or urine sample.