A medical tattoo, a tattoo given for health purposes, is used almost exclusively the following two purposes:
As a warning that a patient suffers from a chronic disease that can exacerbate suddenly and that will require immediate specialist treatment. One example is in the case of congenital adrenal hyperplasia, in which patients may need steroid replacement therapy during ordinary illness.
As an aid in radiotherapy. In order to minimise damage to surrounding tissues, the radiotherapist seeks to keep the irradiated field as small as possible. Marking a number of points on the body with tattoos can aid radiotherapists in adjusting the beam properly.
