For those with access to the pay-per-view site Findmypast, they have recently added original images from the National Archives of WW1 medical records. The blurb reads:

This collection comprises The National Archives’ series, MH106, War Office: First World War Representative Medical Records of Servicemen. Only a sample of the medical records was retained. These records are a representative selection of the full collection of medical records created during the war. Due to data protection, Findmypast has only published records where the admission year is dated back 100 years. For this reason, more records will be released in the coming years. The records include admissions and discharge records from hospitals, field ambulances, and casualty clearing stations. You will also find records from Queen Alexandra’s Military Hospital before the First World War, dating from 1910.