Cannabis therapy : have you tried it? how do you access it? how effective is the treatment for you?

My sister takes cbd oil for anxiety,she has one with thc in it but has told me you can buy one without thc and would be good for me for inflammation and immune effects, has anyone had one without thc,and would it be ok if you had hormone cancer and on tamoxifen ? I was thinking about having one she has with small amount of thc but was concerned about how you go if pulled up and drug tested as she just makes her own and hasn’t got prescribed?