A person may lack mental capacity if something affects how their brain functions. This could be because of:

• a serious brain injury
• an illness, such as dementia
• severe learning disabilities
• a temporary illness such as a chest or urinary infection

Mental capacity can change. For example, someone with dementia or a mental illness may have capacity at some times and not others. A person may also regain mental capacity, for example after a severe stroke or following treatment for a temporary illness.

GOV.UK has advice about how to check whether someone has mental capacity. The website also explains:

• how to represent someone
• when someone can choose you
• how to help someone make decisions
• how to make decisions in someone’s best interests