Capacity & Consent in Adults

🧭 When to assess capacity

Mental capacity is the ability to make a specific decision at the time it needs to be made.

• The Mental Capacity Act 2005 (MCA) governs this in England and Wales.

• Always begin from the presumption of capacity – an adult is assumed to have capacity unless it is established, on the balance of probabilities, that they do not.

Assess capacity only when there is a reasonable doubt about a person's ability to make the decision in front of you, and where that doubt arises from an impairment of, or disturbance in the functioning of, the mind or brain, for example:

• Dementia

• Delirium

• Learning disability

• Acquired brain injury

• Severe mental illness

• Acute confusion

• Intoxication

The assessment is:

• Decision-specific: capacity to consent to a flu jab is not the same as capacity for major surgery

• Time-specific: capacity can fluctuate, so it may be present in the morning but not the evening

For routine, low-stakes care you act on a reasonable belief about capacity; a formal, documented assessment is reserved for significant, serious or contested decisions.

An assessment is not triggered simply because a person:

• Makes an unwise decision

• Carries a diagnosis

• Is judged by their age or appearance

None of these displaces the presumption of capacity.

Source: Mental Capacity Act 2005 · NICE NG108