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What is capacity?

Capacity is the ability to make a decision for yourself. It’s time and decision-specific. This means that whether or not you are able to make a decision depends on when it needs to be made and what the decision is.

So, you might lack capacity to make a decision on one day but be able to make that decision at a later date. This might be, for example, be because you have dementia and your ability to remember information differs from one day to the next.

You might have capacity to make some decisions but not others. For example, you might be able to decide what you want to eat every day but not what will happen if you refuse life-sustaining treatment.

When does someone lack capacity?

You lack capacity to make a decision if:

  • you have an impairment or disturbance of the mind or brain (for example, because you’re unconscious, have dementia, a mental health condition, a brain injury or a stroke)

and because of that impairment, you cannot do one of these things:

  • understand information relating to the decision
  • retain that information for long enough to make the decision
  • take that information into account when making the decision
  • communicate the decision

The law in England and Wales says that people must be assumed to have capacity unless it’s proven otherwise. If a healthcare professional has reason to doubt your capacity, then they’ll need to assess whether you are able to make the decision in question.


Capacity in Scotland and Northern Ireland

The laws in Scotland and Northern Ireland describe capacity slightly differently to the law in England and Wales. Find out more about capacity in Scotland and Northern Ireland.