Capacity is decision-specific and time-specific. Assume capacity unless shown otherwise. A capacitous adult may refuse treatment even if the decision seems unwise. (England and Wales; Scotland and NI differ.)
Five principles
- Presume capacity
- Support the person to decide before concluding they cannot
- An unwise decision does not mean a lack of capacity
- Act in the person's best interests if they lack capacity
- Choose the least restrictive option
Two-stage test
- 1. Is there an impairment of, or disturbance in, the mind or brain?
- 2. Does it mean the person cannot understand, retain, weigh, or communicate the decision?
- Failing any one of the four functional elements means no capacity for that decision
- Fluctuating capacity: assess at the relevant time
Has capacity
- Understands, retains, weighs, communicates
- Decision- and time-specific
- Respect the decision
Lacks capacity
- Fails one or more of the four
- Act in best interests
- Least restrictive, involve family
Deprivation of liberty
- Continuous supervision and control
- Not free to leave
- DoLS or Court authorisation
Process
1
1. Assess for this decision
Assess capacity for the specific decision, now, and document the conversation and your reasoning.
Assess capacity for the specific decision, now, and document the conversation and your reasoning.
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2
2. Maximise capacity
Use plain language, an interpreter or communication aids, the best time of day, and involve someone who knows the person.
Use plain language, an interpreter or communication aids, the best time of day, and involve someone who knows the person.
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3. Best interests
If the person lacks capacity, decide in their best interests: consider past wishes, beliefs and values, consult family and carers, and check for an advance decision, LPA or IMCA.
If the person lacks capacity, decide in their best interests: consider past wishes, beliefs and values, consult family and carers, and check for an advance decision, LPA or IMCA.
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4. Restrictions and emergencies
Deprivation of liberty needs the correct legal authorisation. In an emergency, provide immediate life-saving treatment in the person's best interests.
Deprivation of liberty needs the correct legal authorisation. In an emergency, provide immediate life-saving treatment in the person's best interests.
Also consider
- A valid and applicable advance decision to refuse treatment is binding
- Lasting power of attorney (health and welfare) can consent or refuse
- The Mental Health Act may apply for treatment of a mental disorder
Pitfalls
- Judging capacity on the decision's wisdom
- A blanket 'has or lacks capacity' label (it is decision-specific)
- Not supporting the person to decide first
- Restraining or depriving liberty without lawful authority
MedPrep - www.medprep.uk - Educational revision aid only. Not clinical guidance. Doses are adult examples; check the BNF, current guidelines and local policy, and seek senior advice. Nov 2026