This collection may allow you to discover when and where your ancestor was wounded, where they were treated how long they were held at the medical facility for treatment. Images may provide a variety of additional details such as their service history and a description of wound.
In total, there are now 934,000 records in FindMyPast's collection, which is restricted to records dating back at least 100 years.
The records are from the UK National Archives series MH106 - War Office: WW1 Representative Medical Records of Servicemen, which comprises a representative selection of the full collection of medical records gathered during the war; the sample records were used for statistical purposes. They include admissions and discharge records from hospitals, field ambulances, and casualty stations.