In anticipation of the possibility that the ability to consent may be impaired at a later point, all persons with still existing legal capacity have the ability to grant power of attorney to relatives or other trusted persons (see further Sections 104 and 1896 BGB). The requirement to consent to or reject treatment is in this case prospectively transferred to others.

Powers of attorney represent a written declaration of intent which entitles a person to take over certain tasks and decisions for the person giving the power of attorney under specific circumstances. A precautionary power of attorney is particularly important because it gives the authorized persons the most extensive decision-making powers, including in medical and nursing contexts. In the early stages of dementia, the patient usually still has the legal capacity required to issue a power of attorney. 

If there is no power of attorney (Section 1896(2), sentence 2) and the legal capacity is already impaired, a custodianship order can be issued. The provisions in Sections 1896-1908 BGB on so-called legal custodianship are authoritative in this respect. These regulate, for instance, the appointment of the natural person who acts as the legal custodian of the person who is then incapable of giving consent. The central task of the custodians is to "attend to the affairs of the person under custodianship in a manner that is conducive to his welfare. The best interests of the person under custodianship also includes the possibility for him, within his capabilities, to shape his life according to his own wishes and ideas." (Section 1901(2) BGB).