Abstract: Blood flow restrictors are discussed. In some examples, a restrictor apparatus includes a converging entry portion, a diverging exit portion, and optionally a narrowed portion therebetween to restrict the flow of blood through an arteriovenous graft from a subject's artery to a vein. The structure of the restrictor apparatus decreases the pressure and volume of blood flow between the artery and vein to reduce or prevent hyperplasia or stenosis on the venous side, an increased load on the heart, or blood steal, among other things. The restrictor apparatus can be separate from, but couplable to, the arteriovenous graft. The restrictor apparatus can be integral with the arteriovenous graft. In some examples, the restrictor apparatus can be inserted into the arteriovenous graft in a compressed size and shape, and subsequently be allowed to expand to an uncompressed size and shape. Methods of forming and using the restrictor apparatus are also discussed.