Consent to treatment

Assessing the capacity to consent

All adults are presumed to have sufficient capacity to decide on their own medical treatment unless there is significant evidence to suggest otherwise.

"Capacity" means the ability to use and understand information to make a decision.

Any evidence that a person does not have this capacity has to show both of the following:

  • A person's mind or brain is impaired or disturbed.
  • The impairment or disturbance means the person is unable to make a decision at the current time.

Examples of these conditions include:

  • mental health conditions, such as schizophrenia or bipolar disorder (manic depression)
  • dementia
  • serious learning disabilities
  • long-term effects of brain damage
  • physical or mental conditions that cause confusion, drowsiness or a loss of consciousness
  • delirium (mental confusion)
  • intoxication caused by drug or alcohol misuse

Someone is thought to be unable to make a decision if they are unable to:

  • understand information about the decision
  • remember that information
  • use that information as part of their decision-making process 
  • communicate their decision by talking, using sign language or by any other means

Assessing capacity

Capacity to give consent needs to be assessed at the time that consent is required.

The person’s preferences should be investigated and their agreement to treatment should be sought whenever they are able to make a rational decision. These wishes should be respected if the person cannot give proper consent later on.

If the person lacks capacity and has not previously expressed their wishes, their mental health condition may be treated without consent, as may any related conditions, such as those resulting from self-harm. Unrelated physical conditions cannot be treated without consent.

An advanced decision prohibiting certain types of treatment can be overruled if they are being held under the Mental Health Act (1983), even if they made the advanced decision when they were capable.

Respecting personal beliefs 

If someone makes a decision about treatment that most people would consider to be irrational, it does not mean they have a lack of capacity if they understand the reality of their situation.

For example, a person who refuses to have a blood transfusion because it is against their religious beliefs would not be thought to lack capacity. They still understand the reality of their situation and the consequences of their actions.

However, someone with anorexia (an eating disorder) who is severely malnourished yet rejects treatment because they refuse to accept there is anything wrong with them, would be considered incapable. This is because they are regarded as not fully understanding the reality of their situation.

Self-harm and attempted suicide

In cases of self-harm or attempted suicide where the person refuses treatment and was competent when they harmed themselves, it may be necessary to see if they can be treated without consent under the Mental Health Act (1983). This can happen if a person has a serious mental health condition that requires hospital treatment.

The person's nearest relative or an approved social worker must make an application for the person to be forcibly kept in hospital and treated. Two doctors must assess the person's condition.

Changes in capacity

A person's capacity to consent can change. For example, they may have the capacity to make some decisions but not others, or their capacity may come and go.

In some cases, people can be considered capable of deciding some aspects of their treatment but not others. For example, a person with severe learning difficulties may be capable of deciding on their day-to-day treatment, but incapable of understanding the complexities of their long-term treatment.

Some people with certain health conditions may have periods when they are capable and periods when they are incapable. For example, a person with schizophrenia may have periods when they are considered capable, but they may also have psychotic episodes (when they cannot distinguish between reality and fantasy), during which they are not considered capable.

A person's capacity can also be temporarily affected by:

  • shock
  • panic
  • fatigue (extreme tiredness)
  • medication

If a person knows that their capacity may change, they can make an "advance decision" (previously known as an advance directive), stating any treatments they would like to refuse in case of future incapacity.

If the person specifically states in their advance decision that they do not want to undergo a particular treatment, this is legally binding. The only exception may be if that person is being held under the Mental Health Act (1983). This is an act that allows some people with mental health problems to be compulsorily detained in a psychiatric hospital.

Directgov has more information about understanding the Mental Capacity Act (2005).


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