You have a duty to explain to your patients the risks and benefits of any treatment beforehand. You must also tell them about any alternatives to the treatment and compare the options on offer.
You must explain all this in such a way that the patient can make their own decision about the treatment (where they are able to do so).
The law relating to consent is governed by case law, and evolves on a case-by-case basis except in the case of people who lack the capacity to make their own decisions. Their consent is determined by statute law.
It’s essential that you carefully document the consent process to show that the patient (or their representative) is happy to proceed with treatment.