Capacity Assessment 🧠
On-call guide to assessing mental capacity in the UK under the Mental Capacity Act 2005: two-stage test, practicable support, best interests, LPA/IMCA, and documentation for resident doctors.
🚨 When capacity matters (escalate early)
- Capacity is decision-specific and time-specific. Assess the decision in front of you (e.g. leave hospital, refuse IV antibiotics, consent to CT), not "global capacity".
- Common on-call triggers: self-discharge / leaving against advice, refusing essential treatment or investigations, disputed consent, safeguarding concerns, placement or discharge decisions.
- Escalate to your registrar/consultant early if the decision is high-stakes, capacity is unclear, or there is conflict with family, attorneys, or the MDT.
- Life-threatening emergency with no time to assess or support decision-making: act in the person’s best interests under the MCA, then document and review capacity as soon as practicable.
- Do not use MMSE, MoCA, or a diagnosis alone as a capacity test. Cognitive screens inform the picture; they do not determine capacity.
- MCA applies from age 16 in England and Wales for most decisions. Confirm local Trust SOP and devolved-nation legislation where relevant.
⚖️ Five statutory principles (MCA 2005)
- A person must be assumed to have capacity unless it is established that they lack capacity.
- A person is not to be treated as unable to make a decision unless all practicable steps to help them do so have been taken without success.
- A person is not to be treated as unable to make a decision merely because they make an unwise decision.
- An act done, or decision made, under the Act for or on behalf of a person who lacks capacity must be done, or made, in their best interests.
- Before the act or decision, regard must be had to whether the purpose can be as effectively achieved in a way that is less restrictive of the person’s rights and freedom of action.
🧪 Two-stage test
- Stage 1 (functional): after all practicable support, is the person unable to make this specific decision? They are unable if they cannot do one or more of: understand relevant information; retain it long enough to decide; use or weigh it as part of deciding; communicate the decision by any means.
- Brief retention can still be enough for the decision in question (MCA section 3(3)).
- Stage 2 (diagnostic / causative): is that inability because of an impairment of, or disturbance in the functioning of, the mind or brain (temporary or permanent)? Examples include delirium, dementia, learning disability, mental illness, brain injury, intoxication.
- You must show the causative nexus: why this impairment or disturbance means they cannot make this decision. A diagnosis or label alone is not enough.
- If the person cannot decide because of undue pressure, coercion, or influence rather than an impairment or disturbance, they may still have capacity once that factor is addressed.
- Balance of probabilities: more likely than not that they lack capacity. Record the evidence.
- Capacity can fluctuate. Optimise the environment and reassess when appropriate rather than rushing a permanent conclusion.
📋 How to assess on the ward
- Name the decision clearly (e.g. "capacity to refuse CTPA tonight" or "capacity to leave hospital against medical advice").
- Optimise first: glasses/hearing aids, interpreter, quiet space, pain and nausea control, treat reversible delirium causes, avoid assessing mid-sedation if safe to wait.
- Explain in plain language. Check understanding by asking the person to explain back in their own words (risks of leaving / refusing, benefits of the proposed plan, alternatives).
- Explore values and reasons. An unwise choice with coherent reasoning usually still indicates capacity.
- Who assesses: per MCA Code of Practice, usually the clinician proposing or most concerned with the care or treatment; any staff supporting the person may assess using the two-stage test. Involve seniors for complex or contested decisions; psychiatry/geriatrics when cognitive, psychiatric, or communication issues dominate.
- Check for lasting power of attorney (health and welfare), advance decisions to refuse treatment, Court of Protection deputies, and whether an IMCA is required.
🤝 Best interests, LPA, and advocacy
- If the person lacks capacity for this decision: make a best-interests decision using the MCA checklist (encourage participation; consider past and present wishes, beliefs, and values; consult those interested in their welfare).
- Lasting power of attorney (LPA) for health and welfare: a registered attorney may decide within the LPA’s scope when the person lacks capacity. Ask to see evidence of registration and scope.
- Advance decision to refuse treatment (ADRT): a valid, applicable advance refusal must be followed. Advance statements of wishes should guide best-interests decisions but are not binding in the same way.
- Independent Mental Capacity Advocate (IMCA): instruct when required (e.g. serious medical treatment or long-term accommodation changes for someone without appropriate family or friends to consult). Follow local IMCA pathway.
- Next of kin do not automatically decide for an adult who lacks capacity. Consult them as part of best interests unless an attorney or deputy has legal authority for that decision.
- DoLS / restraint / restriction of liberty: escalate to senior and follow Trust MCA / DoLS / LPS processes. Do not improvise deprivation of liberty on the ward alone.
💬 Outcomes & next steps
- Has capacity: respect a voluntary, informed decision (including refusal), even if you disagree. Document counselling, risks explained, and the person’s understanding.
- Lacks capacity for this decision: proceed in best interests (least restrictive option), involving attorneys, family, and IMCA as required. Involve senior early for high-stakes decisions.
- Unclear or contested: escalate, seek second opinion, involve MSW / psychiatry / legal / safeguarding as per local pathway. Do not coerce.
- If the person wants to leave and has capacity: follow self-discharge / DAMA process. If they lack capacity and leaving is unsafe: escalate immediately; do not simply "let them walk".
- Safeguarding or undue influence concerns: escalate same day via local adult safeguarding / children’s social care / police as required.
📝 Documentation (write this)
- The specific decision assessed and the date/time.
- Information given (risks, benefits, alternatives) and practicable supports offered (interpreter, quiet room, written info, advocate).
- Evidence for each functional element: understand / retain / use or weigh / communicate, with examples of what the person said or did.
- The impairment or disturbance of mind/brain identified, and how it caused the functional inability for this decision.
- Conclusion: has / lacks capacity for this decision at this time (balance of probabilities), and why.
- If lacking capacity: best-interests process, who was consulted (including LPA / IMCA), and the least-restrictive plan. Note when capacity will be reviewed.
Related NICE guidance
NICENICE NG108 — Decision-making and mental capacity (Oct 2018)
Full guidance on nice.org.uk. BetterCall is not endorsed by NICE.
Note Template
Ready-to-use clinical note structure
🕒 08 / 10 / 2026 — 16:07 ATRP re: Capacity assessment Patient: [age] [sex] Admission Dx: [reason for admission] PMHx: [cognitive / psychiatric / neurological / other relevant] Framework: Assisted Decision-Making (Capacity) Act 2015 / HSE National Consent Policy 🧾 Decision assessed (specific, time-bound): • [e.g. capacity to refuse CTPA / leave against medical advice / consent to procedure] • Information given: risks, benefits, alternatives (including doing nothing) 🩺 Context & supports: • Reversible factors addressed: [pain / delirium / sedation / hearing / language / quiet space] • Practicable supports offered before concluding lack of capacity: [interpreter / written info / advocate / decision supporter / time to decide] • Existing arrangements: [DMA / co-decision / representation order / EPA (DSS-registered) / AHD / none known] 🧠 Capacity assessment (Functional test (understand / retain / use or weigh / communicate)): • Understand: [Y/N] — evidence: [...] • Retain: [Y/N] — evidence: [...] • Use / weigh: [Y/N] — evidence: [...] • Communicate: [Y/N] — evidence: [...] 📋 Impression: • [Has / lacks] capacity for this decision at this time • Reasoning: [...] 📌 Plan: • If has capacity: respect decision; document counselling • If lacks capacity: Will and preferences / decision support arrangements / least restrictive option; escalate senior • Review capacity when: [e.g. delirium treated / less sedated] • Senior informed: [ ] 👤 [Your Name], [Role] IMC: _______
Educational reference only. Medical disclaimer