Assessing capacity in patients

A review of the Mental Capacity Act and how to apply it.
Assessing capacity in patients

Author: Colin Tidy, general practitioner, Witney, Oxfordshire. Reviewed by Luke Koupparis, general practitioner, Bristol.

Key learning points

  • An assessment that a person lacks capacity has major implications; it gives clinicians influence over that person, and this influence could, potentially, be abused.
  • An extremely foolish or irrational decision is still a decision and one that the person is entitled to make.
  • A person lacks capacity in relation to a matter if at the material time he/she is unable to make a decision for himself/herself in relation to the matter because of an impairment of, or a disturbance in the functioning of, the mind or the brain.
  • A person must be assumed to have capacity unless it is established that he/she lacks capacity.
  • An assessment of a person’s capacity made in Primary Care may be brief and straightforward and therefore recorded as a brief note within the consultation record. However, every effort should be made to ensure an adequate assessment of capacity rather than personal opinion that cannot be supported.


Making decisions about treatment and care for patients who lack capacity is governed in England and Wales by the Mental Capacity Act 2005, in Scotland by the Adults with Incapacity (Scotland) Act 2000, and in Northern Ireland by the common law.

A seemingly foolish or irrational decision is still a decision and one that the person is entitled to make. Incapacity can only be determined if the person is in fact unable to take the decision in question.

All people aged 16 and over are presumed in law to have the capacity to consent to treatment unless there is evidence to the contrary. If a child is not legally competent then consent is required from someone with parental responsibility, unless it is an emergency. Children aged under 16 years are not automatically legally competent to give consent but can be judged to be legally competent if they have sufficient understanding and maturity to enable them to understand fully what is being proposed.

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