The guidance, Consent: Patients and Doctors Making Decisions Together, focuses on patients whose ability to make decisions is impaired, and has received the backing of both the BMA and the Medical Defence Union.
Doctors are also advised on what to do if a patient does not want to know about their condition or wants someone else to make the decision for them.
The guidance was published in response to legislation passed recently that requires doctors to help vulnerable patients make decisions.
Jane O'Brien, Head of Standards and Ethics at the GMC, said: ‘The relationship between a doctor and a patient should be about partnership, not paternalism. This means that doctors should work with patients to allow them to make decisions tailored to individual views, needs and circumstances, and respect the choices which they make.'