Nothing remains of the large infirmary above ground level. The outer walls are marked out where they would have been. Elderly monks ended their days here and sick monks were cared for. Herbs from the Priory's herb garden were often used to make medicines. Monks had to follow a strict set of Priory rules (based on the Rule of St Benedict) and these allowed better food, including meat, to be provided in the infirmary. If they were able, the sick and elderly monks attended services in the nearby Infirmary Chapel (formerly the First Church).
The infirmary had its own kitchen, toilet and small garden. It was also one of the few buildings in the Priory with fireplaces to provide heat. Monks in the infirmary slept in beds along the walls, but later individual cubicles were added. The Keeper of the Infirmary had a separate room.
Healthy monks were regularly bled in the infirmary or in the warming room below the dormitory. It was believed that blood letting purged the body of impurities and maintained health. Afterwards the monks were allowed to rest and eat the better food served in the infirmary.