GUIDES
Capacity can vary over time. Assess the particular decision when it needs to be made, use practicable support and, where the decision can wait, consider whether the person may be able to decide at a better time.
Capacity can vary over time. Assess the particular decision when it needs to be made, use practicable support and, where the decision can wait, consider whether the person may be able to decide at a better time. Conditions, medication, fatigue and acute illness may affect abilities differently. The report should describe the evidenced pattern and what it means for this particular decision.
Fluctuating capacity describes a situation where a person's ability to make a particular decision varies over hours, days or weeks. The variation may follow a medical pattern, such as delirium resolving with treatment, lucid intervals in dementia, the cycle of a mental illness or the effects of medication, pain, fatigue or substance use. The law does not treat fluctuation as a special category of incapacity. Capacity is assessed for a specific decision at a specific time, so the question is always whether the person can decide the matter in front of them when the decision needs to be made.
Under section 2, the question is the person’s ability at the material time and any causal link to an impairment or disturbance. An earlier opinion is relevant evidence but does not automatically determine a new decision. Consider its scope, any change and what support is now available.
Delirium, dementia, mental illness, some neurological conditions, medication, pain or substance use can affect decision-making over time. A diagnostic label does not establish either fluctuation or incapacity in the individual. Identify the actual pattern from relevant evidence before drawing a conclusion.
The Code of Practice expects decisions to be delayed where capacity is likely to be regained and the decision can wait. Where a decision cannot wait, the assessment addresses capacity at the time the decision must be made. In practice a fair assessment of fluctuating capacity often means choosing the time of day the person is at their best, avoiding periods of acute illness, checking with carers or nursing staff about patterns, and being willing to return. An assessment conducted at a person's worst moment, when a better moment was reasonably available, invites challenge.
Section 1(3) requires all practicable steps to help the person decide before anyone concludes they cannot. With fluctuating presentations this includes assessing during lucid or settled periods, treating reversible causes first where possible, breaking information into stages, using written or visual aids the person can revisit, involving trusted supporters and repeating key information across sessions. The steps taken, and why they were chosen, should be visible in the report.
A single interview is a snapshot, and with fluctuating capacity a snapshot can mislead in either direction. Strong assessments draw on longitudinal evidence: GP and hospital records, care home daily notes, medication changes, family and carer descriptions of good and bad periods, and where appropriate more than one assessment session at different times. The report should say what the pattern of fluctuation looks like, over what cycle, and how the evidence supports that description.
A one-off decision may be made at a time when the person can decide with support. For an ongoing matter, such as managing affairs or conducting proceedings, consider the real sequence of decisions and realistic support across the pattern of fluctuation. Different legal tests may apply: making a will uses Banks v Goodfellow, rather than the MCA test alone.
A court-ready report on fluctuating capacity states the material time it addresses, describes the pattern and likely causes of fluctuation, records when and how often the person was seen, sets out the practicable steps taken, and explains the functional findings and their causal link to the impairment at that time. It should also say whether reassessment is recommended and what trigger should prompt it. Vague conclusions that capacity fluctuates, with no time anchor, are of little use to families, solicitors or the Court of Protection.
Fluctuating capacity does not weaken the Mental Capacity Act framework; it makes disciplined use of it more important. Capacity is always assessed for a specific decision at a specific time, with the person supported to decide at their best realistic moment. Where a decision can wait for capacity to return, it usually should. Where it cannot, a properly timed, properly evidenced and properly recorded assessment protects the person and the decision alike.
Yes. Capacity is time-specific, so a person with delirium, dementia or a fluctuating illness may genuinely be able to make a decision at one time of day and not another. That is why assessors ask carers about patterns and try to see the person at their best realistic time rather than at a moment of crisis.
Where the decision can reasonably wait and capacity is likely to be regained, the Code of Practice expects it to wait. Some decisions cannot be postponed, and for those the assessment addresses capacity at the time the decision has to be made, with every practicable support in place.
There is no fixed number. One supported meeting with adequate evidence may suffice; more may help establish the pattern or provide fair opportunity to decide. The number should follow the person’s needs and the question, rather than a promise that repeat meetings make an opinion immune from challenge.
Later loss of capacity does not by itself undo a decision validly made when the person had capacity. Wills, gifts and LPAs also have separate legal requirements; a capacity opinion cannot establish that every requirement was met.
Not necessarily. If the person can satisfy the capacity requirements at the time the lasting power of attorney is executed, fluctuation before or after does not invalidate it. Timing the execution and evidencing capacity on the day are the practical safeguards, and our separate guide covers borderline and fluctuating capacity when making an LPA.
Record the pattern, causes and practical effects of fluctuation. Plan around better times where possible, decide whether an urgent matter can wait and agree when a material change should prompt review.
These internal links help readers move from this guide to the most relevant Nellie Supports service page, assessment option or legal framework page.
How enhanced reports support court and solicitor scrutiny
Mental Capacity Act 2005: Key Principles Explained
The Two-Stage Test for Mental Capacity Explained
Best mental capacity assessment services in England
Mental Capacity Act 2005, c. 9. Available at: https://www.legislation.gov.uk/ukpga/2005/9/contents
Department for Constitutional Affairs (2007) Mental Capacity Act 2005: Code of Practice. London: The Stationery Office.
39 Essex Chambers, Mental Capacity Guidance Note: Carrying out and recording capacity assessments.
A Local Authority v JB [2021] UKSC 52.
Written by Ben Slater, Registered Social Worker, Founder and Managing Director of Nellie Supports
Reviewed by Kerry Slater, Director of Operations
Last reviewed: 2026-07-21
Author: Nellie Supports Ltd
Publication Date: 15/05/2026
Copyright © 2026 Nellie Supports Ltd. All rights reserved.
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Capacity can vary over time. Assess the particular decision when it needs to be made, use practicable support and, where the decision can wait, consider whether the person may be able to decide at a better time.
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