In order for adults to have a valid consent, a decision must be: “…Given voluntarily by an appropriately informed person…who has the capacity to consent to the intervention in question.”  Moreover informed consent requires the patient to have understood the diagnosis, risks and possible treatment options, which can be explained in broad terms.  However the principle that the patient must only be provided with the relevant medical information in broad terms,  contradicts the principle of autonomy.  A patient may lack the requisite intellectual ability to understand and make an informed decision, which could go unnoticed by a doctor.  Furthermore partial information being provided in broad terms could result in an invalid consent as the focus may be on one aspect of consent.  This reinforces how although adults appear to have the ability to make an autonomous decision, determined on their capacity to choose, in reality this choice has a limitation. In support of this Skegg argues “…information about alternatives will sometimes be at least as important as information about the proposed procedure.”  His argument indicates the unjustified standard medical law imposes by reducing the individual’s freedom of choice, in favour of proceeding with treatment.  Moreover it provides the medical profession with a shield against possible liability, although the differing standards and infringement of personal autonomy can be justified on the grounds that the doctor wishes to fulfil the best interest’s standard,  as established within F v West Berkshire  and prevent loss of life.
If an adult with capacity refuses treatment voluntarily by making an appropriately informed decision, this decision must be respected; demonstrating how the principle of autonomy is upheld.  Lord Donaldson MR in Re T  observes that the presumption for adults is that they have the necessary capacity “…to choose whether to consent to medical treatment, to refuse and…This right of choice is not limited to decisions which others might regard as sensible.”  Alasdair Maclean criticises this argument and emphasises how the courts in fact assess “…the patient’s competence on the basis of the outcome of the choice that he or she has made…”  therefore undermining the principle of self determination.  In addition where a patient does not have the presumed capacity to make a medical decision in the view of the doctor, who carries out both the best interests and incapacity tests, he may be deemed incompetent for simply refusing medical treatment.  This is demonstrated within Re MB  , where Dame Butler-Sloss argues that “…a person lacks capacity if some impairment or some disturbance of mental functioning renders the person unable to make a decision.”  The woman refused a caesarean on the grounds she was a needle phobic, however this was interpreted by the doctor as being a reduction in her capacity, therefore removing her autonomy to choose. This emphasises how a doctor can take advantage of their unfettered discretion, in order to manipulate a patient’s refusal to deem incompetence simply because he disagrees with a decision and does not view it in their best interest. Although it can once again be argued that the paternalistic approach taken by doctors and the court is justified even if the principle for autonomy is undermined in favour of the preservation of life. The difficulty in ensuring a balance between autonomy and the concept of best interest was captured by Dame Butler-Sloss:
“On the one hand to require women who are competent to undergo invasive surgery without consent is unacceptable. On the other hand for a woman with the capacity to make informed decisions in the last stages of pregnancy of a viable foetus to make a decision to deny that unborn child the opportunity to be born raises disturbing issues…” 
This demonstrates the struggle in allowing a patient to exercise autonomy even where a decision, based on “…the reasons for making that choice are rational, irrational, unknown or even non-existent,”  as reiterated by Lord Donaldson.
A minor under the age of sixteen can in certain circumstances consent to treatment irrespective of the parent’s views, providing they are Gillick competent.  Moreover Lord Scarman considers that a “parental right yields to the child’s right to make his own decisions when he reaches a sufficient understanding and intelligence…”  This suggests that minors  are capable of exercising their autonomy to consent to treatment. However the Gillick principle is not reflected within all case law, as show in its application. This illustrates the different standards medical law imposes. Furthermore Lord Donaldson’s obiter statement within Re R  indicates that minor’s rights are limited to consent and not refusal, therefore not fully autonomous in the way expressed by Lord Scarman. He believed that:
“…If a minor was deemed Gillick competent, then the minor, as well as the parents could consent, a concurrent right to consent. Therefore, if the minor can consent the parent does not need to, but if the minor refuses to consent then the parent can consent on the minor’s behalf.” 
Re R illustrates how the purpose of the law of allowing greater self determination, as recognised within Gillick is not being followed. A minor with the necessary maturity has the right to consent, however his parents can override his refusal.  A parent, minor or the court can consent on behalf of the minor as illustrated by Lord Donaldson’s ‘key holder’ analogy  and later through the ‘flat jacket’ analogy. 
It is difficult to justify why a mature minor’s autonomous decision to refuse, can be overridden on the presumption that parents can more effectively asses difficult legal and ethical issues.  This is an example of the double standards mature minors are subject to. Kennedy agrees arguing “the right to refuse is the most critical element of the right to self determination.”  Moreover “overcoming a refusal can be recognised as being a possible infringement of a person’s autonomy both bodily and intellectually, therefore a person’s refusal should be given greater weight than a consent.”  This would ensure that mature minors have the ability to make their own decisions by validly refusing treatment, without this being overridden; ensuring that autonomy is respected.  Rachel Taylor suggests that the autonomy of a mature minor could be protected further by granting “…more limited powers of consent to parents, such that they could only overrule a child’s refusal where the child’s decision put her life and health in serious danger.”  Gillian Douglas also recognises that if a child has a sufficient level of maturity, then surely their ability to consent is part of their right to determine. 
Both Lord Fraser and Lord Scarman however recognised the importance for parents to be involved in the decision-making process that is in the child’s best interests.  Moreover, the courts determination in wanting to protect a child’s irrational decision, can justify removing autonomy and the different standards medical law imposes, if it ultimately protects the child,  as shown within Re L.  Within this case, the fourteen year old child could potentially give up her strong religious beliefs, therefore it was for the court to intervene and preserve her ‘best interests’ by indentifying her limited experience of lie. 
In conclusion, the role of the doctor is of such importance that in most cases an adult patient would agree with the doctor, therefore reducing in certain circumstances the adult’s ability to make an ‘informed consent.’ Moreover an adult’s refusal can be interpreted as being a reflection of their incompetence when in fact it is an exercise of their autonomy, demonstrating the unjust standards that exist.
For minors, the Gillick competent principle empowers the doctor and only allows a minor to consent, therefore illustrating little autonomy. Section 8 of the Family Law Reform Act 1969 does not allow mature minors to refuse treatment, therefore not upholding the right to self determination.  If the courts want to give autonomy to minors and those under eighteen, this distinction between refusal and consent needs to be removed, in order to make medical law standards justified. However Lord Scarman was referring to contraceptives within Gillick, therefore may not have been suggesting a broader medical principle, illustrating the need to have a balance within the law. 
Although medical law imposes a higher standard for minors to refuse by holding that “any consent suffices for treatment, but only unanimous refusal can prevent it,”  it can be argued that these different standards are justifiable on the grounds that the courts since Gillick are concerned with the minor’s welfare.  Moreover despite their maturity and understanding, society wants to protect them.  This paternalistic approach doctors and the court want to pursue is indentified by Lord Fraser: “…the doctor must be satisfied that giving contraceptive advice and treatment without parental knowledge or consent is in the minor’s best interests.”  However it is vital that wherever possible, an adult or minor who has the required intelligence and understanding has their autonomy protected to the highest standard