• Implied consent
• Expressed consent

Consent to treatment may be implied or it may be specifically expressed either orally or in writing. The clinical situation determines the approach required.

Implied consent
Much of a physician's work is done on the basis of consent which is implied either by the words or the behaviour of the patient or by the circumstances under which treatment is given. For example, it is common for a patient to arrange an appointment with a physician, to keep the appointment, to volunteer a history, to answer questions relating to the history and to submit without objection to physical examination. In these circumstances consent for the examination is clearly implied. To avoid misunderstanding, however, it may be prudent to state to the patient an intention to examine the breasts, genitals or rectum.

The foregoing notwithstanding, in many situations the extent to which consent was implied may later become a matter of disagreement. Physicians should be reasonably confident the actions of the patient imply permission for the examinations, investigations and treatments proposed. When there is doubt, it is preferable the consent be expressed, either orally or in writing.

Expressed consent
Expressed consent may be in oral or written form. It should be obtained when the treatment is likely to be more than mildly painful, when it carries appreciable risk, or when it will result in ablation of a bodily function.

Although orally expressed consent may be acceptable in many circumstances, frequently there is need for written confirmation. As physicians have often observed, patients can change their minds or may not recall what they authorized; after the procedure or treatment has been carried out, they may attempt to take the position it had not been agreed to or was not acceptable or justified. Consent may be confirmed and validated adequately by means of a suitable contemporaneous notation by the treating physician in the patient's record.

Expressed consent in written form should be obtained for surgical operations and invasive investigative procedures. It is prudent to obtain written consent also whenever analgesic, narcotic or anaesthetic agents will significantly affect the patient's level of consciousness during the treatment.