Why Jose Rizal called as a doctor?

José Rizal was called a doctor because he earned a medical degree from the Universidad Central de Madrid in 1887. His thesis was titled "On the Constitutional and Therapeutic Action of the Root Bark of Pangawian on Dysentery." He also studied ophthalmology in Europe and became skilled in eye surgery. He returned to the Philippines and practiced medicine until he was exiled in 1896 for his political activities.