When should capacity be assessed?

Most everyday healthcare decisions do not require a formal capacity assessment. Clinicians normally work from the presumption that adults can decide. A structured assessment becomes necessary when there is a genuine reason to doubt the person’s ability to make the specific decision.

The reason for doubt should be factual: for example, acute confusion, marked inconsistency that cannot be explained by changing preferences, inability to grasp material information despite support, or a significant decision in the context of an impairment that may affect decision-making.

Acute illness, delirium, hypoxia, medication effects, intoxication, severe distress or a new neurological event can justify closer assessment. So can evidence that the person repeatedly misunderstands the nature or consequences of a decision despite explanation.

The seriousness and complexity of the decision matter to the depth of assessment, not because high-risk choices automatically mean incapacity, but because the relevant information and consequences may be more demanding.

Age, disability, mental illness, dementia, learning disability, residence in a care home, homelessness, a “difficult” personality or professional disagreement are not sufficient reasons on their own. Refusal is also not a trigger by itself.

When a person says no, first explore why. They may have misunderstood the proposal, fear a side effect, prioritise a different goal, have experienced previous harm, or simply value the risk differently. Assessment should not be weaponised to overcome refusal.

The assessment should be proportionate to the decision. A simple, low-consequence choice may require a brief focused conversation. A complex decision about major surgery, discharge to a restrictive setting or refusal of life-sustaining treatment may require more detailed information, time, support and documentation.

Proportionality also means avoiding unnecessary legalistic processes when the person is clearly making the decision and no reasonable doubt exists.

Urgency changes what can reasonably be done. Where immediate treatment is needed to prevent serious deterioration, there may be little time for repeated assessment or external consultation. The clinician should still involve the person as far as possible, record the reason for concern, and act under the applicable legal framework.

Where the decision can safely wait, urgency should not be manufactured for organisational convenience.

A capacity conclusion is tied to the circumstances in which it was reached. Improvement in delirium, new communication support, a change in treatment options or a different decision may require reassessment. Conversely, deterioration can create a new reason to assess.

A good plan records the trigger for review rather than leaving a capacity label to follow the person indefinitely across settings.

Use the search box in this module to jump to these terms and related concepts.

• trigger
• doubt
• assessment
• diagnosis
• disagreement
• risk
• urgent decision
• proportionate
• clinical change

Record the factual observations that created reasonable concern about ability to make one specific decision, avoiding judgemental language.

Use current official sources for further reading. Links open the issuing organisation.

• MC-EW-01 — Mental Capacity Act 2005
• MC-EW-02 — Mental Capacity Act Code of Practice
• MC-S-03 — Adults with incapacity: code of practice for medical practitioners
• MC-NI-01 — Mental Capacity Act (Northern Ireland) 2016
• MC-NI-02 — Mental Capacity Act - Department of Health NI
• CON-UK-01 — GMC - Decision making and consent

Sources checked through 17 September 2026. High-volatility legal topics must be rechecked before patient-specific decisions.