How to assess best interests

Advice on assessing best interests when patients can't consent to treatment.

If a patient requires medical treatment but lacks the capacity to consent to it, the treating doctors may need to make a decision based on their best interests.

Assessment of capacity, and of best interests, is set out in the Mental Capacity Act (MCA) 2005 and its accompanying Code of Practice. These provide a framework for caring for or treating people 16-years old or over in England and Wales who lack the ability to make decisions for themselves.

This guide examines the law and guidance in England and Wales.

Members are welcome to contact us for further advice on assessing the best interests of patients in Scotland and Northern Ireland.

Legal framework

Cases where patients may lack capacity but need medical treatment can be very challenging. We’ve previously issued advice on assessing a patient's mental capacity, which covered some key points, including that, decisions made or action taken for or on behalf of a person who lacks mental capacity must be done in their best interests.

The concept of best interests and how to assess this can be confusing and it’s important to note that 'best interests' is not defined by the MCA or the accompanying Code of Practice. Instead, the legislation provides broad principles and a framework to enable individuals to work through a process then reach a decision tailored to the particular situation.

Taking an individual approach

The individualised approach is well summarised in the judgement of Aintree University Hospitals NHS Foundation Trust v James [2013]. Recognising the difficulty in making these individual decisions the Supreme Court explained:

"The most that can be said, therefore, is that in considering the best interests of this particular patient at this particular time, decision-makers must look at his welfare in the widest sense, not just medical but social and psychological; they must consider the nature of the medical treatment in question, what it involves and its prospects of success; they must consider what the outcome of that treatment for the patient is likely to be; they must try and put themselves in the place of the individual patient and ask what his attitude to the treatment is or would be likely to be; and they must consult others who are looking after him or interested in his welfare, in particular for their view of what his attitude would be."

The decision therefore must be the one which the healthcare professional reasonably believes is right for the individual patient in question. It is not about what might be thought generally to be the best medical approach.

Define the decision

Chapter 5 of the MCA Code of Practice provides a checklist of factors to consider when working out best interests. However, before working through the checklist below, it's important to define the decision to be made along with the various options and choices available.

In emergencies, it will almost always be in the person's best interests to give urgent treatment without delay. With a key exception to this being that a valid, applicable advance decision  to refuse such treatment is in place (see below).

Best interests checklist

The below checklist sets out the steps to take when arriving at a best interests decision.

  • You should make every effort to encourage and enable the person who lacks capacity to take part in the decision making.
  • Try to identify things the person would take into account, if they could make their own decision.
  • Try to find out the person’s views: their past and present wishes, feelings, beliefs and values and anything else they would be likely to consider as part of the decision-making process.
  • You must not make assumptions about someone's best interests based simply on age, appearance, condition or behaviour.
  • You should consider if there is a possibility the person will regain the capacity to make a particular decision. If so, then it may be possible to put off the decision until this occurs if it is not urgent.

The views of others who are close to the person who lacks capacity should be considered, including those caring for and interested in the patient's welfare, as well as the views of any attorney or deputy, and anyone named by the patient to be consulted - while being mindful of the patient's right to confidentiality. These people may have information about the person’s wishes and feelings, beliefs and values. 

If there is nobody who fits into these categories, involve an IMCA (independent mental capacity advocate) for decisions about major medical treatment. It may be useful to have a best interests meeting, involving those caring for the patient, family members, and those interested in patient's welfare (or an IMCA). 

If some are unable to attend, they may be able to participate virtually or supply information in writing. A written record should be made of the meeting.

  • Choose the option that is least restrictive of the person’s rights, where that is possible meeting their best interests.
  • Special considerations apply to decisions about life-sustaining treatment (see below).

Weigh all of this up to work out what is in the person’s best interests.


There are also two important exceptions to when the best interest principles will apply:

  1. when the patient has previously made an advanced decision to refuse medical treatment. Provided the advance decision is valid and applicable to the situation and there is no evidence that the patient has since changed their mind, it should be respected even if it leads to a course of action, or inaction, not considered to be in their best interests
  2. certain situations when a patient who lacks capacity might be involved in research. Chapter 11 of the Code of Practice goes into further detail about the circumstances surrounding this exception.

Life-sustaining treatment

Decisions around life-sustaining treatment and best interests can be extremely difficult. It is important not to make assumptions about someone’s quality of life, and anyone involved must not be motivated by a desire to bring about the person’s death. 

Advance decisions to refuse life-sustaining treatment are not always valid and applicable, and must be considered carefully. Seek support if you are faced with such a situation and call us for advice.


It’s important to keep clear records of the process by which the patient's best interests were established, including steps taken to involve the patient. It should be clear from the record how the decision about the person's best interests was reached and what the reasons for making that decision were. Records can include:

  • what circumstances were considered
  • what values, wishes and beliefs have been accounted for
  • which other individuals have been consulted as part of the assessment, and what their views and observations were
  • other aspects of the case you considered when going through this process.

Careful documentation will ensure there is a clear picture of the patient's care and it can also aid you if you are called on to justify your decision. It may well be valuable to set out a list of the pros and cons, with the risks and benefits, and what has been done to reduce any risks, together with the conclusion as to what option is in the patient's best interests and why.

Some reassurance

While the principles and process may seem daunting, the Mental Capacity Act includes protections for those who can demonstrate having made a decision in the reasonable belief it was in the best interests of the person who lacks capacity, applying the checklist described above. 

Remember to get further direction from your trust legal team or from us if you're uncertain how to proceed in individual cases.

Members can contact our advisers here.

This page was correct at publication on 21/10/2022. Any guidance is intended as general guidance for members only. If you are a member and need specific advice relating to your own circumstances, please contact one of our advisers.

Dr Ellie Mein MDU medico-legal adviser

by Dr Ellie Mein Medico-legal adviser


Ellie joined the MDU as a medico-legal adviser in 2013. Prior to this she worked as an ophthalmologist before completing her Graduate Diploma in Law in Birmingham.

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