Making healthcare decisions in a person's best interests when they lack capacity: clinical guidance based on a review of evidence.

Objective: To clarify the concept of best interests, setting out how they should be ascertained and used to make healthcare decisions for patients who lack the mental capacity to make decisions.

Context: The legal framework is the Mental Capacity Act (MCA) 2005, which applies to England and Wales.

Theory: Unless there is a valid and applicable Advance Decision, an appointed decision-maker needs to decide for those without capacity. This may be someone appointed by the patient through a Lasting Power of Attorney, or a Deputy appointed by the court. Otherwise the decision-maker is usually the responsible clinician. Different approaches exist to surrogate decision-making cross-nationally. In England and Wales, decision-making is governed by the MCA 2005, which uses a person-centred, flexible best interests (substituted interests) approach.

Observations: The MCA is often not followed in healthcare settings, despite widespread mandatory training. The possible reasons include its focus on single decisions, when multiple decisions are made daily, the potential time involved and lack of clarity about who is the responsible decision-maker.

Solution: One solution is to decide a strategic policy to cover more significant (usually health-related) decisions and to separate these from day-to-day relational decisions covering care and activities. Once persistent lack of capacity is confirmed, an early meeting should be arranged with family and friends, to start a process of sharing information about the patient's medical condition and their values, wishes, feelings and beliefs with a view to making timely treatment decisions in the patient's best interests.