Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 110. Treatment and Care of the Wounded, Sick and Shipwrecked
Section B. Distinction between the wounded and the sick
The UK LOAC Pamphlet (1981) states: “Priority in the order of medical treatment is decided only for urgent medical reasons.” 
United Kingdom, The Law of Armed Conflict, D/DAT/13/35/66, Army Code 71130 (Revised 1981), Ministry of Defence, prepared under the Direction of The Chief of the General Staff, 1981, Section 6, p. 22, § 2.
(emphasis added)
The UK LOAC Manual (2004) states:
7.3. The wounded and sick are to be protected and respected. They may not be attacked. They must be treated humanely. They must be provided with medical care. They may not wilfully be left without medical assistance nor exposed to contagious diseases or infection. Priority of treatment is dictated by medical reasons only …
7.3.2. Paragraph 7.3 applies to all wounded and sick, whether United Kingdom, allied or enemy, military or civilian. They are entitled to respect and protection, humane treatment and, to the fullest extent practicable and with the least possible delay, the medical care and attention required by their condition. It is forbidden, for example, to give the treatment of United Kingdom and allied wounded priority over the treatment of wounded enemy personnel. The only distinction which is permitted in dealing with the wounded or sick is that founded on real medical need. There is no absolute obligation on the part of the military medical services to accept civilian wounded and sick – that is to be done only so far as it is practicable to do so. For example, the commander of a field hospital placed to deal with casualties from an impending battle would be entitled to refer non-urgent cases elsewhere, even if the hospital had the capacity to treat them at the time. Once the treatment of a civilian patient has commenced, however, discrimination against him on other than medical grounds is not permissible. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, §§ 7.3 and 7.3.2.
With regard to priority of treatment, the manual states:
There must be no discrimination on grounds of sex, race, nationality, religion, political belief or any other similar test. Spies, saboteurs, partisans and illegal combatants who are wounded or sick are entitled to the same treatment. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 7.3, footnote 4.
In its chapter on maritime warfare, the manual further states: “The wounded, sick and shipwrecked … must be provided with medical care … Priority of treatment is dictated by medical reasons only.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 13.129.
In its chapter on internal armed conflict, the manual states: “The wounded, sick and shipwrecked must be … given the medical treatment they need without discrimination for non-medical reasons.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 15.29.1.