The scientific method varies from field to field. In medicine you usually need to proof it by taking a significant amount people. Then create a control group and a testing group. Then test your medicine on the group and give the other placebos.

When you can measure health improvement for one group over the other there is a reasonable amount of proof that the medicine works.

The scientific method has one major goal. Reduce human made errors in science. Humans do not work objectively. Humans always have an bias. Things like reproduceable tests and peer review try to reduce the bias.