Duty of doctors heavier than the will of patients

Last time when I went to hospital I was asked to drop a signature stating I fully understand the risk and benefit about the use of blood products. Because the products not only have effect but also risks of infection by hepatitis viruses. Doctors need to have us write a confirmation because this risk is inevitable in using this medicine. If I couldn't sign their document, they won't use it.

In the case of some religious sect member's refusing to accept blood transfusion and blood products has nothing to do with whether it's safety or risky from this medical perspective. They refuse it because of their belief. But from doctor's eyes, this is merely a belief based not upon the medical viewpoint.

In spite of the gap between my case and their cases, it's unceratain how doctors react in this case. Some doctors respect any patient's will and won't use blood, but others use any means including using blood transfusion, products against the will of patients. Are those who got recovered from illness going to sue doctors for their using treatments other than the patients chose? If sued, probably doctors will lose in spite of the fact that they saved patient's lives. Patients or their family can't sue doctors for not using any means including those of patients asked them not to use even if the patients died. Certainly doctors won't run a risk of using treatments the patients asked them not to use. But the queation here is, is it against the ethics of doctors not to have used any measures? Are doctors ought not to use some treatment judging from the fact that merely based on patient's belief?