Yes it is a blood test, usually just a vial-maybe 2 depending on the laboratory. You could probably have a family doctor order it. A CF clinic is a good idea but it also depends on how your brother was diagnosed and if he had ever had a blood test, but you said you were unaware of his mutations. I woudl actually recommend that both you and he get tested. It is good to know your mutations, it will certainly apply to him if he ever wants to have children.