Informed consent is a patient's voluntary agreement to a proposed intervention, given with capacity and after receiving the information a reasonable person in their position would want in order to decide. It is both an ethical requirement grounded in respect for autonomy and a legal one: proceeding without valid consent may constitute battery or negligence.
Three conditions must be satisfied. The person must have capacity to make that particular decision at that particular time. The decision must be voluntary and free from coercion or undue pressure. And it must be informed, meaning the person understands the nature and purpose of the intervention, its material risks and benefits, the reasonable alternatives and the option of doing nothing.
In the UK, the 2015 Supreme Court judgment in Montgomery v Lanarkshire Health Board changed the legal test for disclosure. The question is no longer what a responsible body of clinicians would disclose, but whether a reasonable person in the patient's position would attach significance to a risk, or whether the clinician should reasonably be aware that this particular patient would. Consent is therefore a dialogue, not a recital of statistics.
Capacity is decision-specific and presumed unless demonstrated otherwise. Under the Mental Capacity Act 2005 in England and Wales, a person lacks capacity if they cannot understand, retain, weigh or communicate a decision. Where capacity is absent, decisions are made in the person's best interests, taking account of their known wishes, values and any valid advance decision or appointed attorney.
A signed consent form is evidence that a conversation happened, not a substitute for it. Good practice is to record what was discussed, the specific risks raised, the alternatives considered and any questions asked. Digital consent platforms can improve consistency, provide accessible information in advance and create a clear audit trail, provided they support genuine two-way discussion rather than reducing consent to a click-through.
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