Capacity planning in Canada is provincial, and the terminology shifts as you cross a border even though the underlying purpose is identical. In Ontario the governing statute is the Substitute Decisions Act, 1992, which permits a power of attorney for personal care, while the consent your attorney later gives or refuses is governed by the Health Care Consent Act, 1996. The document must be signed and dated by the grantor in the presence of two witnesses, and a witness cannot be the attorney, the attorney's spouse, the grantor's spouse or child, or anyone under eighteen. Get the witnessing wrong and the appointment can fail entirely, which is the most common reason these documents are challenged.
British Columbia takes a different route. There the Representation Agreement Act replaces the personal care power of attorney with a representation agreement, available in a standard Section 7 form for routine and minor health matters and an enhanced Section 9 form that reaches major medical decisions and the refusal of life support. A Section 9 agreement requires full capacity at signing; a Section 7 can be made even by an adult with reduced capacity, which makes BC unusually flexible. Alberta uses yet another label, the personal directive under the Personal Directives Act, which combines the appointment of an agent with written instructions in a single document.
Across every common-law province the document only bites once incapacity is established, and certain decisions stay off limits no matter how the instrument is drafted: a representative in BC cannot consent on your behalf to Medical Assistance in Dying, and committal under mental health legislation is carved out everywhere. The federal and provincial materials gathered in the Government of Ontario guide to powers of attorney under the Substitute Decisions Act set out the Ontario forms and registration position in full. Because the rules diverge so sharply, the safest practice is to execute the document for the province where you actually live, and to refresh it if you move.