Skip to textbook content
Doctor’s PassportTextbook
TopicsAll topics

Loading topic navigation…

Textbook navigation
TopicsAll topics

Loading topic navigation…
← Psychiatry indexChapter sections
Purpose and principlesIndications, selection and cautionsMethod and interpretationClinical next stepsRisks, monitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
Full textbook9 sectionsOpen only what you need
Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Decision-specific capacity assessment

Psychiatry · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

RapidFull
!
Urgent treatment while capacity is uncertain

Life-threatening illness may require action before delirium resolves, communication is fully restored or legal documents are located, but urgency does not create unlimited authority.

Action: Provide immediate communication and reversible-factor support, define the decision and search for a valid refusal or authorised proxy. If delay would cause serious harm and no binding refusal is known, give only necessary proportionate treatment under the applicable emergency or best-interests framework while verification and senior legal review continue.

Purpose and principles

Assess whether a person can make one defined decision at the required time after all practicable support, apply the correct jurisdiction's legal test, and distinguish incapacity from diagnosis, detention, communication difficulty or an unwise choice.

Capacity identifies who decides, not whether clinicians approve the choice. Start with a real decision: accepting antibiotics today, returning home tonight or allowing disclosure to a relative. State the information material to that choice and avoid testing irrelevant facts. Presume the person can decide, choose the best time and environment, treat pain, hypoxia, infection, withdrawal or delirium, and provide language, sensory and communication support. Involve a trusted supporter when the person wants this and it does not create coercion.

In England and Wales, the Mental Capacity Act 2005 requires an impairment or disturbance in the functioning of mind or brain and a causal functional inability. The person is unable to decide if they cannot understand, retain, use or weigh relevant information, or communicate the decision by any means. Information includes reasonably foreseeable consequences of choosing or declining options. Record which ability failed, the evidence, support attempted and how the impairment caused that difficulty. A cognitive test can inform but never replace this interview.

Indications, selection and cautions

Capacitous disagreement

The person understands and compares material consequences and communicates a stable choice despite selecting an option professionals regard as risky.

Supported ability

Performance improves with interpreter, visual information, optimal timing, treatment of delirium or an established assistive communication method.

Causal weighing failure

An impairment prevents the person from applying or comparing a material consequence, with concrete responses demonstrating the link in the relevant jurisdiction.

Fluctuating capacity

Ability changes with arousal, intoxication, mania, medication or fatigue, making timing, safe delay and repeated assessment clinically important.

Global-label error

The record describes the person as lacking all capacity without naming the decision, timing, information, support or functional evidence.

Red flags requiring action

  • Age, diagnosis, psychosis, detention, intoxication, learning disability, communication impairment or an apparently irrational outcome cannot alone establish lack of capacity.
  • In England and Wales, inability must result from an impairment or disturbance in functioning of mind or brain; functional difficulty without the causal link does not complete the statutory test.
  • A person may lack capacity for one complex treatment decision while retaining capacity for another choice, and capacity may recover after delirium, intoxication or acute distress improves.

Method and interpretation

  1. 01
    Decision and material-information definitionFirst step
    Why
    Specify the actual options, benefits, harms, no-action consequence and decision deadline.
    Interpretation and limitations
    A general capacity assessment is not valid. Information and complexity should be proportionate to the decision actually being made.
  2. 02
    Practicable-support assessment
    Why
    Optimise language, communication, timing, environment, sensory input and reversible clinical factors.
    Interpretation and limitations
    If a barrier can be corrected, the person may decide. Record support tried and why any further step was impracticable or unsafe to delay.
  3. 03
    Functional capacity interview
    Why
    Test understanding, retention, use or weighing and communication using the person's own explanation.
    Interpretation and limitations
    Record responses and the effect of support. In England and Wales, connect any inability causally to impairment or disturbance of mind or brain.
  4. 04
    Fluctuation and timing review
    Why
    Determine whether ability may improve and whether the decision can safely wait.
    Interpretation and limitations
    Delay preserves autonomy when clinically safe; urgency justifies only necessary temporary action and does not prove global incapacity.
  5. 05

Clinical next steps

01Capacity assessmentSupport first and test one decisionFirst stepThere is a genuine reason to doubt ability for a specific healthcare or welfare choice.+
  1. 1Define the decision, material information and urgency and identify the applicable UK jurisdiction and possible impairment.
  2. 2Provide practicable communication and clinical support, then ask the person to explain and compare options and communicate a choice.
  3. 3Record each functional ability, causal reasoning where required, actual responses, support, conclusion and when reassessment is needed.
02Fluctuating abilityRestore conditions and choose timingDelirium, intoxication, mood state, fatigue or medication may cause capacity to change.+
  1. 1Treat reversible factors and identify the person's optimal time, familiar communication method and suitable supporter.
  2. 2

Risks, monitoring and follow-up

  • Reassess when the decision, material information, risk, impairment or timing changes; previous incapacity is not a permanent status.
  • Track delirium, intoxication, pain, hypoxia, infection, sleep and medicines that can alter attention and weighing ability.
  • Review whether interpreters, hearing aids, accessible formats and communication specialists were provided consistently across settings.
  • Verify that proxy authority remains valid and covers the particular health-and-welfare decision rather than relying on family title or finance powers.
  • Audit records for decision specificity, actual patient responses, causal reasoning, support attempts and jurisdictionally correct documentation.

Special situations

Outcome is not ability

A person can choose serious risk when they understand and weigh it, while a seemingly sensible choice may still be made without capacity.

Support can be decisive

Treatment of delirium, an interpreter or eye-gaze communication can change who lawfully makes the decision rather than merely improve bedside manner.

Retention may be brief

Long-term recall is not required when information can be held long enough to use it for the choice under consideration.

Detention and capacity differ

Mental-health legislation may authorise specific assessment or treatment despite capacitous objection, while many other decisions remain the patient's own.

Jurisdiction is clinical data

The patient's location and governing law determine forms, proxy powers and safeguards, so cross-border assumptions can invalidate an otherwise careful assessment.

Common pitfalls

  1. 01

    Assessing general capacity instead of naming a real decision and deadline.

  2. 02

    Finding incapacity because a person disagrees or chooses a high-risk option.

  3. 03

    Using a cognitive score as the statutory functional assessment.

  4. 04

    Testing before providing interpreter, sensory aids, pain relief or suitable timing.

  5. 05

    Failing to link functional inability to impairment where the governing test requires causation.

  6. 06

    Assuming detention removes capacity or next of kin can consent automatically.

  7. 07

    Applying England-and-Wales forms in Scotland or Northern Ireland without local verification.

Practice

Two practice questions

Your practice draft is saved in this browser.

Question 1 of 2
0 correct
PsychiatryOriginal SBA

Risky but capacitous choice

An adult with schizophrenia accurately explains a proposed operation, compares benefits with bleeding risk and consistently refuses because avoiding transfusion is a deeply held value. What should the clinician conclude?

Choose one answer, then submit
← Rapid synopsisBack to overviewAll Psychiatry topics →
Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • Mental Capacity Act 2005England-and-Wales capacity, best-interests, advance decision and proxy framework.
  • NICE NG108 mental capacity recommendationsSupported decision making, assessment, recording and best-interests practice.
  • Adults with Incapacity Scotland Act 2000Distinct Scottish incapacity principles and authority.
  • Mental Capacity Northern Ireland Act 2016Northern Ireland statute with phased implementation requiring current local verification.
  • GMC decision making and consentCommunication, capacity, emergencies and lawful treatment decisions.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom
Use or weigh is not a requirement to reason like a clinician. Explore whether the person can compare material consequences and apply them to themselves. Values, fear, religious belief and tolerance of risk legitimately influence choice. A delusion may selectively prevent weighing one consequence while leaving other decisions intact; conversely, a person with psychosis may understand and compare treatment options fully. Brief retention is enough if information can be held for the decision. Communication disability requires alternative methods, not an automatic incapacity finding.

Capacity varies with decision and time. If acute mania, intoxication or delirium is likely to improve and delay is safe, restore conditions and reassess. When urgent treatment cannot wait, determine what immediate intervention is necessary and whether a valid applicable advance refusal or authorised decision maker exists. Use the least restrictive lawful route and continue to involve the person. Reassess when physiology, information or choice changes; do not copy a conclusion about one decision into another.

Jurisdictions differ. Scotland uses the Adults with Incapacity (Scotland) Act 2000 and its principles, definitions, certification and proxy structures rather than the England-and-Wales MCA process. Northern Ireland's Mental Capacity Act (Northern Ireland) 2016 has phased commencement alongside other local law and policy. Clinicians must use current organisational forms and specialist legal advice, especially for serious treatment, restraint, deprivation of liberty or cross-border care.

Key points

  • Define the exact decision, available options, material benefits and harms, consequences of no action and the time by which it must be made.
  • Presume capacity and take all practicable steps to support the decision through timing, treatment of reversible factors, interpreter, sensory aids, simple language and communication technology.
  • In England and Wales, identify an impairment or disturbance of mind or brain and ask whether, because of it, the person cannot understand, retain, use or weigh, or communicate relevant information.
  • Short retention can be enough; communication can use speech, sign, writing, gesture, eye gaze or assistive technology.
  • Ask the person to explain choices, consequences and reasoning in their own words; record actual responses rather than a conclusory capacity present or absent statement.
  • An unwise, risky or values-based choice can be capacitous. The test concerns the decision process, not agreement with professional advice.
  • If capacity fluctuates and the decision can safely wait, reassess at the person's optimal time; urgent harm may require a proportionate temporary decision process.
  • If capacity is absent, check valid advance refusals, health-and-welfare attorney or deputy powers, court orders and the correct best-interests or jurisdiction-specific pathway.
  • Mental-health detention does not itself remove capacity, and ordinary physical treatment unrelated to mental disorder still needs its own consent or capacity authority.
  • Failure to provide interpreter, hearing aids, accessible information, pain relief, time or a suitable communication method can create a false incapacity conclusion.
  • Capacity law is not identical across the UK: do not transpose Mental Capacity Act forms or terminology into Scotland or Northern Ireland without current local verification.
    • Authority and jurisdiction check
    Why
    Identify the applicable national law, advance decision, welfare proxy, deputy or court order.
    Interpretation and limitations
    Verify document validity, applicability and scope. Finance authority or informal next-of-kin status does not automatically authorise healthcare decisions.
    Delay a non-urgent decision when safe and repeat the interview rather than treating one impaired period as permanent.
  • 3For urgent harm, make only necessary proportionate arrangements under the correct framework while continuing efforts to restore participation.
    • 03Capacity absentIdentify lawful decision maker and safeguardsSupported assessment shows the person cannot make the specified decision under the applicable test.+
    1. 1Check valid advance refusals, welfare attorney or deputy authority, court directions and whether the decision can wait for recovery.
    2. 2Use the jurisdiction-specific best-interests, benefit or substitute-decision process and involve the person and appropriate consultees.
    3. 3Select the least restrictive effective option, document dissent and seek specialist legal review for serious dispute, restraint or liberty restriction.