Capacity and Consent: What Is the Difference?

On placement, you will often hear healthcare professionals discussing capacity and consent in the same conversation. The two concepts are closely connected, but they do not mean the same thing.

The easiest way to remember the difference is:

Capacity is the ability to make a particular decision.
Consent is the person’s voluntary agreement to what happens next.

Understanding that distinction helps protect a person’s autonomy and ensures that care is delivered lawfully and ethically.

The Legal Frameworks

Different legal frameworks apply across the UK.

In England and Wales, decision-making for adults who may lack capacity is governed principally by the Mental Capacity Act 2005.

In Scotland, the relevant framework is the Adults with Incapacity (Scotland) Act 2000. Scotland does not use the Mental Capacity Act’s “best interests” test. Instead, any intervention under the Scottish Act must follow its statutory principles, including benefit, minimum intervention, consideration of the adult’s wishes and consultation with relevant others.

Northern Ireland has its own legal framework. The Mental Capacity Act (Northern Ireland) 2016 has been only partially commenced, so healthcare professionals must follow current Health and Social Care policy and applicable law.

What Is Capacity?

Capacity is a person’s ability to make a specific decision at the time it needs to be made.

It is not an all-or-nothing label. Someone might be able to decide what to eat or whether to have their blood pressure checked but be unable to understand a complex decision about major surgery.

Capacity can also fluctuate because of factors such as delirium, medication, pain, fatigue or acute illness. If a decision can safely wait until the person is better able to participate, delaying it may be appropriate.

The Mental Capacity Act Test

Under the Mental Capacity Act 2005 in England and Wales, a person lacks capacity if an impairment or disturbance in the functioning of the mind or brain means they are unable to make the particular decision.

A person is considered unable to make the decision if they cannot:

• understand the relevant information
• retain it long enough to decide
• use or weigh it as part of the decision
• communicate their decision by any available method

Before concluding that someone lacks capacity, professionals must take practical steps to support them. This might include using simpler language, visual aids, an interpreter, hearing equipment or choosing a quieter time and environment.

A person must not be treated as lacking capacity simply because they make a decision other people consider unwise.

Capacity in Scotland

Scottish law also requires capacity to be considered in relation to the particular decision or action.

The Adults with Incapacity (Scotland) Act describes incapacity in terms of being unable to act, make decisions, communicate decisions, understand decisions or retain the memory of decisions because of mental disorder or an inability to communicate due to physical disability.

Difficulty speaking does not automatically mean incapacity. Every reasonable effort should be made to support communication before deciding that a person cannot make the decision.

What Is Consent?

Consent is the voluntary agreement a person gives before a treatment, examination, procedure or other aspect of care takes place.

For consent to be valid, the person must:

• have capacity for the particular decision
• receive the information they need
• understand the reasonable options, benefits and material risks
• decide voluntarily, without pressure or coercion

Consent is a process, not merely a signature.

A signed form can provide evidence that a discussion took place, but it does not make consent valid if the person did not understand the decision, lacked relevant capacity or was placed under pressure.

Consent may be expressed verbally, in writing or through clear behaviour. For example, a person may hold out their arm after a blood-pressure check has been explained. Their actions may communicate agreement, but staff should not assume consent without first explaining what they intend to do.

The amount of information and documentation required should be proportionate to the decision. Complex or higher-risk procedures require a more detailed discussion and record.

The Key Difference

Imagine a patient is being offered an operation.

The healthcare professional must first support the patient to understand the procedure, its expected benefits, important risks, reasonable alternatives and what could happen without treatment.

If the patient can understand, retain, use or weigh that information and communicate a decision, they have capacity for that decision. They can then consent or refuse.

Signing the form is not the moment capacity suddenly appears. The meaningful conversation and the person’s decision are what matter.

What If a Person Has Capacity but Refuses?

An adult with capacity can refuse treatment, even when professionals or relatives believe the decision is unwise or may lead to serious harm.

The team should make sure that the person understands the relevant information, has been offered appropriate support and is not being pressured. The discussion, decision and any escalation should be documented clearly.

A refusal should not automatically trigger the conclusion that the person lacks capacity.

Providing non-emergency treatment after a capable person has clearly refused may have serious legal and professional consequences. The exact legal terminology differs across UK jurisdictions, so it is safer than broadly describing every case as “battery or assault.”

A refusal may require urgent senior or legal advice in particularly complex circumstances, but disagreement alone does not cancel the person’s autonomy.

What Happens When a Person Lacks Capacity?

The answer depends on where the care is being provided.

England and Wales

Under the Mental Capacity Act 2005, decisions made for someone who lacks capacity must be made in their best interests.

This involves considering the person’s wishes, feelings, beliefs and values; whether capacity may return; all relevant circumstances; and the views of appropriate people involved in their life.

The aim is not simply to choose what professionals think is medically best. Nor is it solely to guess what the patient would have chosen. It is a structured, person-centred legal decision.

The team should also check for:

• a valid and applicable Advance Decision to Refuse Treatment
• a Health and Welfare Lasting Power of Attorney with relevant authority
• a court-appointed deputy with relevant powers
• the need for an Independent Mental Capacity Advocate

Scotland

In Scotland, non-emergency medical treatment for an adult who lacks capacity is commonly authorised under Section 47 of the Adults with Incapacity (Scotland) Act 2000.

An authorised healthcare professional must assess the person’s capacity and complete the appropriate certificate. Any intervention must benefit the adult, be the least restrictive reasonable option and take account of the person’s past and present wishes.

The team must also check whether a welfare attorney, welfare guardian or intervener has relevant powers. Some treatments require additional safeguards and cannot be authorised by a routine Section 47 certificate.

Emergency treatment necessary to preserve life or prevent serious deterioration may be provided under common law when consent cannot be obtained.

Does the Family Decide?

Family members can provide valuable information about the person’s wishes, values and usual communication. They should be consulted when appropriate.

However, being a spouse, adult child or “next of kin” does not automatically give someone legal authority to consent to or refuse treatment for another adult.

Formal authority may come from arrangements such as a Lasting Power of Attorney in England and Wales or a welfare power of attorney or guardianship order in Scotland. The documentation must be checked because the person’s powers may be limited to particular decisions.

Why This Matters for Student Nurses

Capacity and consent appear throughout ordinary nursing care, not only during surgery or major treatment.

You may encounter them when:

• taking observations or blood samples
• supporting medication administration
• providing personal care
• involving a patient in student learning
• discussing discharge arrangements
• caring for someone who is confused or refusing treatment

As a student, you should explain your role and ensure that the person agrees to your involvement. A patient has the right to refuse student observation or participation without this affecting their care.

If you are unsure whether consent is valid, or whether someone can make the particular decision, pause and speak to your practice supervisor or the registered professional responsible for the person’s care.

Bleepbook Memory particular Line

Capacity asks: “Can this person make this decision now?”

Consent asks: “Have they freely agreed after receiving the information they need?”

One does not automatically prove the other and a signed form is never a substitute for a meaningful conversation.

References

Adults with Incapacity (Scotland) Act 2000. Available at: UK Legislation

Department of Health Northern Ireland. Mental Capacity Act. Available at: Department of Health NI

General Medical Council. Decision making and consent. Available at: GMC

Mental Capacity Act 2005. Available at: UK Legislation

National Health Service. Consent to treatment. Available at: NHS

National Institute for Health and Care Excellence (2018). Decision-making and mental capacity (NG108). Available at: NICE

Nursing and Midwifery Council. The Code: Professional standards of practice and behaviour for nurses, midwives and nursing associates. Available at: NMC

Scottish Government. Adults with incapacity: code of practice for medical practitioners. Available at: Scottish Government