The duty of care concept is a common law legal principle which underpins all healthcare interactions. However, evidence within the Australian context suggests misuse of this common law principle as a justification for non-consensual coercive treatment. Misuse seems to occur particularly where patients have impaired decision-making capacity and/or refuse treatment. In this article, we discuss the emerging evidence of misuse, which arguably reflects healthcare practitioner confusion between the doctrines of ‘duty of care’ and ‘necessity’, and posit that cognisance of lawful substitute consent processes are lacking. We then discuss the concept of duty of care as an obligation, as opposed to a power, before presenting the elements of a valid consent and legislation relating to substitute consent, which allow health practitioners to proceed with treatment. We conclude this article with a discussion of the circumstances where treatment may be given without consent.