Assessing the capacity to make decisions is a fundamental part of dementia care, ensuring that an individual rights are protected while their safety is maintained. In a clinical context, mental capacity is not a general label but is instead specific to a particular decision at a particular time. A person with dementia may have the capacity to decide what to wear or eat but may lack the capacity to manage complex financial investments or consent to a major surgical procedure.
The assessment process is guided by the principle that capacity must be assumed unless proven otherwise. Clinicians use a structured, evidence based framework to determine if a person’s brain can process the information necessary to make a choice. This guide explores the functional tests used in 2026 to assess capacity, the legal principles involved, and how families can support their loved ones through this sensitive process.
What we will discuss in this article
- The core principles of the Mental Capacity Act
- The two stage functional test for assessing capacity
- Understanding information and the ability to retain it
- The process of weighing up risks and benefits in reasoning
- Communicating a decision and the role of support
- The importance of decision specific and time specific assessments
- emergency guidance for identifying signs of health deterioration
The principles of capacity assessment
Before a formal assessment begins, clinicians must adhere to five key principles designed to safeguard individual autonomy.
The first principle is the presumption of capacity. No person should be treated as lacking capacity simply because they have a diagnosis of dementia or because they make a decision that others view as unwise. Furthermore, every effort must be made to help the person make their own decision before they are deemed to lack capacity. This might involve using simpler language, visual aids, or choosing a time of day when the person is most alert, a crucial consideration for those with fluctuating conditions like Lewy body dementia.
The two stage functional test
Clinicians perform a structured assessment to determine if an impairment in the brain is directly affecting the decision making process.
Stage 1: The diagnostic test
The assessor must first confirm that the person has an impairment of, or a disturbance in the functioning of, the mind or brain. In this context, a formal diagnosis of Alzheimer disease, vascular dementia, or another neurodegenerative condition satisfies this first stage.
Stage 2: The functional test
This stage looks at whether the impairment means the person is unable to make a specific decision. To have capacity, the individual must be able to do all four of the following:
- Understand the information relevant to the decision.
- Retain that information long enough to make the decision.
- Use or weigh that information as part of the process of making the decision.
- Communicate their decision by any means, including speech, sign language, or simple gestures.
Evaluating reasoning and communication
The most complex part of the assessment often involves checking if the person can weigh up the consequences of their choice.
A person might be able to understand the facts of a medical treatment but may be unable to weigh the risks of declining it against the benefits of accepting it. Clinicians look for consistency in the person’s reasoning. For instance, if a person with dementia refuses life-saving medication because they believe it is poison, despite evidence to the contrary, their ability to use and weigh information is impaired. The assessment also ensures that the person can communicate their choice clearly. If a person can only give inconsistent or contradictory answers, they may be found to lack capacity for that specific decision.
Decision specific and time specific nature
Capacity is never a permanent or blanket status; it is always tied to a specific moment and a specific task.
| Decision Type | Complexity | Assessment Focus |
| Daily Living | Low | Can the person choose a meal or clothing? |
| Financial | Medium/High | Can they understand the value of money and bills? |
| Medical | High | Do they understand the risks of a procedure? |
| Legal | High | Do they understand the implications of a Will? |
Because dementia is often progressive, capacity must be reassessed for new or significant decisions. A person may lose the capacity to drive safely while still being perfectly capable of deciding where they wish to live. Clinicians and families must work together to identify when a person needs a new assessment as their condition changes.
To summarise
Assessing decision-making capacity in dementia is a rigorous process that balances the protection of a person’s rights with the need for their safety. By following the functional test of understanding, retaining, weighing, and communicating, clinicians can determine if a specific decision can be made by the individual. It is essential to remember that capacity can fluctuate and is specific to each task. Supporting individuals to make their own choices for as long as possible is a core goal of clinical care, ensuring that dignity and autonomy remain at the heart of the dementia journey.
emergency guidance
Acute medical situations often require immediate decisions when capacity is in question. Call 999 or seek urgent clinical help if a person with dementia experiences a sudden onset of extreme confusion, a severe fall, or a loss of consciousness. In an emergency, if a person lacks the capacity to consent to life-saving treatment, clinicians are legally empowered to act in the person’s best interests to preserve life and prevent serious harm. Any rapid decline in a person’s ability to communicate or understand their surroundings should be treated as a medical emergency, as it may indicate delirium or an acute stroke rather than a permanent loss of capacity.
Can a person with dementia still sign a Will?
Yes, if they have testamentary capacity at the time of signing. This is a specific legal assessment that determines if they understand what a Will is and the extent of their estate.
Who performs a capacity assessment?
The person proposing the action usually performs the assessment. This could be a GP for medical treatment, a social worker for care arrangements, or a solicitor for legal matters.
What if the family disagrees with the assessment?
If there is a dispute, a second opinion can be sought from a specialist such as a psychiatrist or a geriatrician. In complex cases, the Court of Protection may make the final decision.
Does a Power of Attorney mean the person has no capacity?
No. An attorney only makes decisions if and when the person lacks the capacity to do so themselves. Many people with a Power of Attorney continue to make their own daily decisions.
Can capacity return?
In some cases, yes. If the lack of capacity was caused by a temporary issue like a urinary tract infection or dehydration, capacity may return once the underlying condition is treated.
How can I help my relative during an assessment?
Ensure they have their hearing aids and glasses, choose a quiet environment, and use simple, clear language to explain the decision being discussed.
Authority Snapshot
Dr. Rebecca Fernandez is a UK trained physician with an MBBS and experience in general surgery, cardiology, internal medicine, gynecology, intensive care, and emergency medicine. She has managed critically ill patients, stabilised acute trauma cases, and provided comprehensive inpatient and outpatient care. In psychiatry, Dr. Fernandez has worked with psychotic, mood, anxiety, and substance use disorders, applying evidence based approaches such as CBT, ACT, and mindfulness based therapies. Her skills span patient assessment, treatment planning, and the integration of digital health solutions to support mental well being in 2026.
