The medical facilities varied greatly depending on size. Smaller ships might have a single doctor - or even just a Sick Berth Attendant (SBA) without a medical degree. Larger ships had larger sick bays, with more facilities, multiple doctors and sometimes even a dentist. To give more information, I'll look in detail at two classes of ships; the 'River' class frigates as an example of smaller ships, and the battlecruiser HMS Hood for larger ships.

The Royal Navy divided its medical personnel into two categories. Surgeons were trained doctors, usually recruited from civilian practice. After receiving their medical degrees and joining the RN, they would, in peacetime, undergo a six-month course in naval medicine. This taught things like preventative medicine and casualty treatment, which were usually not covered in detail in civilian medical schools. In wartime, the training dropped to just two weeks. Surgeons were officers, but were not expected to command. The RN also had enlisted medical personnel. These were the Sick Berth Attendants (SBA)s. SBAs were not expected to have any medical experience or training before joining the Navy. Instead, they would undergo a nine-twelve month course at one of the three main naval hospitals (in Chatham, Portsmouth or Plymouth). This course dropped to just ten weeks in 1939, by removing theoretical study, and stayed at this length for much of the war - though it was increased to twenty weeks for some time. SBAs were expected to serve as ward orderlys and nurses on larger ships, and as something like a paramedic on smaller ships. On the smallest ships - the 'Flower' class corvettes for example - an SBA would be the only man with extensive medical training aboard. Some SBAs were given more thorough and specialised training for roles like X-ray technicians, but they were only found on the largest ships or in the naval hospitals aboard.

The 'River' class frigates were built as escorts for Atlantic convoys, entering service from the middle of 1941. They were fairly typical of the RN's smaller ships, in terms of provision of medical equipment. They had a crew of 107 men as originally designed, though this soon rose as new equipment was fitted; their typical crew during their period of service was ~140. Of these, just two had deep medical training, with one surgeon-lieutenant and one SBA. They worked out of the ship's sick-bay, found on the port side of the upper deck amidships. It was a medium-sizd cabin, measuring 15ft by 12ft 6". It had two swinging cots, and could fit three-four camp beds to extend the capacity. There was a folding operating table, normally kept stowed. There was good provision for medical equipment, with a large amount of storage space, plus electric and steam sterilisers and an electric kettle. It was well-lit and well ventilated, with two portholes, a skylight, an electric fan and six louvres for the ship's forced ventilation system. The sick-bay on the 'River's was generally well-respected by the surgeons who served on them.

Hood, meanwhile, had a crew of ~1,400, ten times that of the 'River's. Her medical department hadn't quite increased in proportion, but the facilities at their disposal had. Hood's medical department consisted of four officers and six SBAs. There was a Surgeon-Commander in overall command, with two Surgeon-Lieutenants and a dental Surgeon-Lieutenant under him. The six SBAs included a Chief Petty Officer in command and two Sick Berth Stewards, who typically carried out nursing tasks. Hood's sick-bay was on the starboard side of the upper deck, forwards of A turret. The main compartment had twelve swinging cots, plus space for more camp beds or hammocks. This served as the main ward. Adjoining it was an isolation ward, used for infectious diseases, or for injured junior officers. Treatment could be done in an examination room, or in a well-equipped operating room. There was also an X-ray set in its own cabin, and a dispensary for storage of drugs and medicine. Medical equipment, bedding and bandages could be sterilised in a dedicated 'disinfector house', on the boat deck aft of the after funnel. The dental surgery was on the boat deck beneath the bridge structure. Casualties suffered in action could be brought to one of two Medical Distributing Stations for first aid. These were positioned on the lower decks, between each of the two pairs of turrets. Here, the wounded could receive first aid treatments before being sent to the sick-bay for further treatment if needed. Hood had completed in 1920, so by 1939, her medical facilities were somewhat inadequate. The more modern King George V class battleships had a sick-bay with 22 cots (four of which were in an isolation ward), with space for eight hammocks or twelve or more stretchers.