This is an appeal arising from a decision by the Tennessee Board of Nursing (“the Board”) to revoke a registered nurse’s license after she retrieved the wrong medication from an automatic dispenser and administered it to a hospital patient, resulting in the patient’s death. The Tennessee Department of Health (“the Department”) brought an initial complaint against the nurse concerning the incident, which it first determined did not merit further action but then later re-opened. Simultaneously, the nurse faced criminal prosecution and was ultimately convicted of two criminal charges related to the incident. Following a contested hearing in the administrative proceedings, the Board revoked the nurse’s license. The nurse sought judicial review of this decision pursuant to Tennessee’s Uniform Administrative Procedure Act. During the judicial review proceeding, the nurse raised, for the first time, the doctrines of res judicata and collateral estoppel as affirmative defenses to the Department’s complaint. In response, the Board argued that the nurse had waived these affirmative defenses because she had failed to raise them during the administrative proceedings. While the petition for judicial review remained pending, the criminal case moved to the sentencing phase. A doctor, who had testified as an expert witness in both the contested administrative proceeding and the criminal case, wrote a letter of support for the nurse to the criminal court judge in preparation for her sentencing. When the nurse learned of the doctor’s supportive letter, she moved the trial court to remand the instant case to the Board so that the Board could consider the contents of the letter in its decision. The trial court declined to remand the matter to the Board or to allow the nurse to present the letter to the Board as additional evidence. The trial court subsequently entered a final order, determining that the nurse had not waived the affirmative defenses of res judicata or judicial estoppel but declining to reverse the Board’s decision on those grounds. The trial court then affirmed the Board’s decision to revoke the nurse’s license. The nurse has appealed. Upon review, we determine that the nurse waived the affirmative defenses of res judicata and collateral estoppel because she failed to present those doctrines during the administrative proceedings Accordingly, we reverse the trial court’s determination concerning waiver of those defenses. In all other respects, we affirm.