Best Interests Decisions Under the Mental Capacity Act 2005

Mr Lewis is 78 and has been admitted with pneumonia. He is also delirious. When the doctor explains that he needs intravenous antibiotics, he pulls his arm away and says he is going home.

His daughter is worried. She tells the team that he has dementia and says, “I’m his next of kin. Can’t you just give him the antibiotics?”

You could easily hear a conversation like this on placement. A patient is refusing something the team thinks they need, their capacity is being questioned and a relative is trying to help. But who actually gets to decide?

In England and Wales, this is where the Mental Capacity Act 2005 comes in.

Before anyone decides for Mr Lewis, can he decide for himself?

Mr Lewis has dementia and he is delirious, but neither diagnosis automatically means he lacks capacity.

The team needs to look at the decision in front of him: does he understand what the antibiotics are for, what could happen if the pneumonia is not treated and the options available to him? Can he retain that information long enough to decide, use or weigh it when making the decision and communicate what he wants?

They also need to help him as much as they reasonably can. If he cannot hear properly because his hearing aids are sitting in the bedside drawer, that needs sorting. If he is frightened, in pain or too distracted to follow a rushed explanation, those things matter too. Capacity is not supposed to be tested by giving somebody information once and seeing whether they cope with it.

And because delirium can fluctuate, timing matters. Mr Lewis may be much clearer later in the day or after his infection begins to improve.

If he can make the decision, it remains his decision. He can even refuse treatment that the clinical team or his daughter think he should have. Making a decision other people think is unwise does not, on its own, mean someone lacks capacity.

Best interests only enters the picture if Mr Lewis cannot make this particular decision himself.

He cannot make the decision. What happens now?

After being supported and assessed, Mr Lewis cannot currently understand and weigh the information he needs to decide about the antibiotics. His delirium is severe and the treatment cannot safely wait in the hope that he will be clearer tomorrow.

Someone now has to make a decision about his treatment.

This is the bit that can become confusing because “best interests” can sound as though it simply means choosing whatever treatment is medically best. It does not.

Section 4 of the Mental Capacity Act requires much more than that. The clinical facts obviously matter. The team needs to understand what the antibiotics are likely to achieve, what could happen without them and what burdens the treatment may bring. But they also need to know something about Mr Lewis himself.

What has he said about treatment in the past? What matters to him? What is he saying now? Are there beliefs or values that would have influenced his decision? Is he likely to regain capacity? Could the decision safely wait? Can he still be involved in parts of the discussion even though he cannot make the final decision?

That is why a best interests decision is about more than treating the pneumonia. The person with the pneumonia still matters.

Where does his daughter fit into this?

Mr Lewis’s daughter tells the team that her dad hates hospitals. Since his wife died, staying in his own home and looking after himself has been hugely important to him. But she also remembers him saying that he would accept short-term hospital treatment if it meant he had a good chance of getting home again.

That is useful information.

What she cannot do is consent to the antibiotics simply because she is his daughter or because she is listed as his next of kin.

“Next of kin” is commonly recorded in healthcare, but it does not automatically give a relative legal authority to make treatment decisions for an adult who lacks capacity. The family can still be an important part of the discussion because they may know the patient far better than the clinical team does.

So rather than asking Mr Lewis’s daughter, “Do you want us to treat him?”, the useful conversation is about her dad: “What do you think he would have wanted? What matters to him?”

There is a big difference between those two questions.

What if she says she has power of attorney?

Then the team needs to check it.

A health and welfare lasting power of attorney can give an attorney authority to make certain decisions when the person no longer has capacity, but the document matters. The team needs to know what powers were actually granted and whether they cover the decision being made.

The same applies if somebody says they are a Court of Protection deputy. A deputy does not have unlimited authority simply because they have a court order. Their powers are set out in that order.

There may also be a decision Mr Lewis made himself while he had capacity. For example, a valid and applicable advance decision to refuse a particular treatment can be legally binding. If one applies, it is not something the team can simply ignore because they now believe another option would be better for him.

This is why titles such as “next of kin”, “attorney” and “deputy” should not all blur into “the family decides”. They mean very different things.

How is the actual decision made?

In Mr Lewis’s case, there is no relevant advance decision and nobody has a health and welfare lasting power of attorney or court order covering the treatment. The clinician responsible for the treatment therefore has to decide whether giving the antibiotics is in his best interests.

They know the pneumonia could worsen without treatment. They know the antibiotics offer a realistic benefit. They also know Mr Lewis is distressed by what is happening.

His daughter has helped them understand that getting home and remaining independent matter greatly to him. His current words and behaviour still matter too. Losing capacity does not make him disappear from his own care.

The team therefore continues trying to involve him. They approach him when he is calmer, explain things again, make sure he can hear them and consider whether there is a reasonable way of giving the necessary care with less distress or restriction.

This is where the Mental Capacity Act principle of using the less restrictive option becomes practical. It is not about automatically doing less. It is about asking whether the same aim can reasonably be achieved while interfering less with the person’s rights and freedom.

For Mr Lewis, the decision is eventually made to treat the pneumonia. But the legal reasoning is not simply:

He lacks capacity + antibiotics are good = give antibiotics.

The team has had to establish that he cannot make this decision, consider whether it can wait, check whether anybody else has relevant legal authority, involve him as far as possible, find out what matters to him and consider the available options before reaching the decision.

What if nobody knows Mr Lewis?

Imagine he had no daughter, close friend or other appropriate person to speak to about his wishes.

For certain serious medical treatment and longer-term accommodation decisions, an Independent Mental Capacity Advocate (IMCA) must be involved when the legal criteria are met and there is nobody appropriate to consult.

An IMCA is there to support and represent the person in the decision-making process. They can gather information, make sure the person’s circumstances and wishes are properly considered and challenge the proposed decision where appropriate. They do not simply become a replacement relative or take over every decision.

And if everyone still disagrees?

Sometimes the difficult part is not deciding that a patient lacks capacity. It is what happens afterwards.

A relative may believe the patient would never have wanted the proposed treatment. The clinical team may believe the alternative carries unacceptable risk. There may be disagreement about what the patient previously said, or even about whether they lack capacity at all.

Those disagreements need to be taken seriously rather than reduced to “the family is being difficult” or “the professionals know best”. A best interests meeting may help everyone work through the same decision and the evidence behind it. Senior review, a second opinion, advocacy, mediation, ethics support or legal advice may be needed depending on the situation.

Where a serious dispute cannot be resolved, the Court of Protection can make decisions about capacity and best interests.

As a student nurse, you are not expected to settle that argument or interpret complex legal documents yourself. But you may be the person standing beside Mr Lewis when he repeatedly says no. You may hear the daughter say she is next of kin. You may notice that everyone is talking about what is “best” for him without anyone asking what he would have wanted.

Those are things worth noticing and raising with the registered nurse supervising you.

Back to Mr Lewis

Mr Lewis receives treatment for his pneumonia. As the infection improves, his delirium begins to settle. His capacity is reviewed rather than assuming that because he lacked capacity yesterday, he still lacks it today.

That last part matters.

A best interests decision was needed because, at that point, he could not make that particular decision himself. It did not permanently transfer control of his healthcare to his daughter or the clinical team.

That is probably the easiest way to understand best interests on placement: first work out whether the patient can make the decision. If they cannot, the decision still has to be made around that patient, not around whoever happens to be standing beside the bed.

References

Great Britain (2005) Mental Capacity Act 2005. London: The Stationery Office.

Department for Constitutional Affairs (2007) Mental Capacity Act 2005 Code of Practice. London: The Stationery Office.

Office of the Public Guardian (2026) Making decisions: a guide for people who work in health and social care. London: Office of the Public Guardian.

Bleepbook is an educational resource for student nurses. Local policy, senior clinical advice and appropriate legal guidance should be followed in individual cases.