Adults with decision-making capacity have the right to decide what can be done to their bodies. This means they can consent to medical treatment or refuse it.
This page explores the law relating to consent to treatment, and when an adult will have capacity to make decisions about medical treatment.
The law on consent to treatment for children is different from the law about adults. For information about the law relating to children and consent to treatment visit the Children and end of life decision-making page.
Consent to medical treatment
Why is consent to treatment needed?
Valid consent is generally needed before medical treatment can be provided to a competent adult, except in some limited circumstances (discussed below). The need for consent means a competent adult can also decide to refuse medical treatment.
A health professional who treats without consent could be liable under civil or criminal law (e.g. being charged with assault), or be subject to disciplinary action.
What is valid consent to treatment?
For consent to be valid:
- the person must have capacity to give consent to the treatment;
- the person must provide that consent freely and voluntarily; and
- the consent must apply to the treatment to be given.
A voluntary decision is one made freely by the person, without undue pressure, coercion or manipulation. In Re T (Adult: Refusal of Treatment) the court considered a case of undue influence in medical treatment decision-making.
Appropriate advice and decision-making support from the person’s family and health professionals will not be undue influence, provided the person is still making the decision they want.
Are there formal requirements for consent?
Consent can be given verbally or be implied e.g. if a person offers their arm so that a health professional may suture a laceration.
Information should also be provided to the person about treatment risks as well as any other information a person would need to consent to treatment.
When is a person’s consent to treatment not required?
Generally, health professionals should obtain a person’s consent prior to giving treatment, or undertaking any medical examination.
However the person’s consent is not required when:
When will a person have capacity?
The law presumes that all adults have capacity to consent to or refuse treatment, unless it is shown otherwise.
The common law test is that a person will have capacity to make decisions about medical treatment if they are able to:
- comprehend and retain the information needed to make the decision, including the consequences of the decision; and
- use and weigh that information as part of their decision-making process.
Information about treatment can include the proposed treatment and alternatives, and the consequences and risks of different treatment options.
Guardianship and medical treatment legislation in the different States and Territories also establishes specific capacity tests and recognises the need for consent to treatment. Most are similar to this common law approach but some have additional requirements.
What if a person is making decisions that others disagree with?
An adult with capacity can make decisions that others disagree with. This includes a decision to refuse life-sustaining medical treatment which is clinically recommended (this issue was considered in the case of Re B (Adult: Refusal of Medical Treatment)).
This is because capacity is assessed in relation to a person’s ability to make a decision and not what decision they make. However, unwise or unusual decisions may be a prompt to check a person’s capacity. If doubts remain after further assessment, a court or tribunal can be asked to assess a person’s capacity.
Can a person’s capacity be different for different decisions and change over time?
A person may have capacity to make some decisions but not others. For more serious decisions, such as refusing life-sustaining treatment, the process of understanding, retaining and weighing the information (and risks involved) will be more complex than for more minor decisions, such as consenting to a flu vaccine.
Assessments of capacity are based on the decision to be made so a finding of total incapacity is not common (except, for example, when a person is unconscious).
A person’s capacity to make a decision can also change over time. For example, a person may have fluctuating capacity because of some forms of dementia or mental illness. Capacity will be judged at the time a treatment decision is required. For example, in Re C (Adult: Refusal of Medical Treatment) the Court decided that a person’s mental illness did not affect his decision-making capacity in relation to life-sustaining treatment.
Re T (Adult: Refusal of Treatment)  Fam 95
T was 34 weeks pregnant when she was involved in a car accident. Her baby did not survive a subsequent emergency caesarean section. T’s mother was a Jehovah’s Witness and on two occasions after visiting with her mother, T spontaneously advised health professionals that she did not wish to receive blood products. T had assumed that there were other products that would be a satisfactory substitute for blood should a transfusion be necessary. This was not the case, and T needed a blood transfusion to save her life. Her father and partner sought the Court’s approval for a transfusion to be administered on the grounds that T’s capacity was diminished, and that her refusal to consent was invalid due to the overwhelming influence of her mother. The judge authorised the transfusion.
The decision was appealed to a higher court, which found a number of factors had combined to produce a decision to refuse blood products that was not truly T’s. These included the traumatic accident, the death of her child, T’s severe pain and suffering and the influence of medication, as well as the nature of the mother and daughter relationship. On these grounds the Court decided T had not provided a valid refusal of consent, and that it was lawful for the hospital to administer the blood transfusion.
Re B (Adult: Refusal of Medical Treatment)  2 All ER 449
B suffered a haemorrhage of the spinal column in her neck. After further treatment and relapses, she became paralysed from the neck down and required a ventilator to live. B later requested the ventilator be removed.
The Court noted this case was only about B’s capacity to decide whether the ventilator should be removed. It was not about whether she should live or die, or her best interests. The Court found that B had capacity for the decision. Her capacity was assessed based on her decision-making process and not the outcome of her decision. Underpinning this conclusion was that B could give a clear explanation of her decision-making process, and demonstrated understanding of her condition and its consequences.
Re C (Adult: Refusal of Medical Treatment)  1 WLR 290
C was serving a prison sentence for attempted murder. While in prison, he was diagnosed with chronic schizophrenia, and was transferred to a secure psychiatric facility. He developed a necrotic leg ulcer so severe that medical advice was to amputate the leg below the knee.
C’s doctors advised he had only a 15% chance of survival without an operation and relying only on conservative treatment. C said he would rather die with two feet than live with one, and refused consent to the amputation. He did agree to more conservative treatment, after which his condition improved and he was no longer at risk of imminent death. C’s solicitor then asked the hospital to agree not to amputate in the future. The hospital would not agree to this so C applied to the Court to prevent the amputation of his leg without his written consent.
The Court said the question was one of capacity to consent to treatment, not the merits of his decision. It found no link between C’s delusions as a result of the schizophrenia and his refusal to undergo the treatment. Although C may have lacked capacity for other decisions, in relation to the proposed operation he knew and understood what it involved and the risks of not having it. The Court decided that C could lawfully refuse the amputation of his leg and so the hospital would need his permission if it wanted to operate.
Richards B. General principles of consent to medical treatment. In: White B, McDonald F, Willmott L, editors. Health Law in Australia. 3rd ed. Sydney: Thomson Reuters, 2018.
Byrne, M, White, B, McDonald, F. A new tool to assess compliance of mental health laws with the Convention on the Rights of Persons with Disabilities. International Journal of Law and Psychiatry 2018; 58: 122-142.
Purser, K, Rosenfeld, T. Evaluation of legal capacity by doctors and lawyers: the need for collaborative assessment. Med J Aust 2014; 201(8): 483-485.
Medical Board of Australia. Good Medical Practice: A Code of Conduct for Doctors in Australia. 2014: 3.5, 3.8.