Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 26. Medical Activities
Section B. Respect for medical secrecy
The UK LOAC Manual (2004) states:
[A] a person engaged in medical activities [may not] be compelled “to give to anyone belonging either to an adverse Party, or to his own Party except as required by the law of the latter Party, any information concerning the wounded and sick who are, or who have been, under his care, if such information would, in his opinion, prove harmful to the patients concerned or to their families.” However, regulations for the compulsory notification of communicable diseases must be respected. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 7.14.1.
With regard to non-international armed conflicts in which the 1977 Additional Protocol II is applicable, the manual states:
“Under no circumstances shall any person be punished for having carried out medical activities compatible with medical ethics, regardless of the person benefiting therefrom.” This general principle is expanded in three areas.
b. The professional obligations of persons engaged in medical activities regarding information which they may acquire concerning the wounded and sick under their care, shall, subject to national law, be respected.
c. Subject to national law, no person engaged in medical activities may be penalized in any way for refusing or failing to give information concerning the wounded and sick who are, or have been, under his care. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 15.46.