You can do a test at home using an "Eldon" kit. I did it this past weekend and it was pretty easy (other than getting the blood out). You get these special card

You can do a test at home using an "Eldon" kit. I did it this past weekend and it was pretty easy (other than getting the blood out). You get these special cards with reagents on that react with type A and type B blood as well as Rh+ and -, then the combination of the reactions tells you the blood type. In my case it was very obvious as the blood on the "anti B" card went very clotted whereas on the "anti A" card it was very smooth, placing me as type A.