It depends on the site of the creation, the diameter of the vein, and the blood flow in the vein. Usually, it takes within 4 to 6 weeks for a vein to get large enough and strong enough to be able to withstand cannulation and the high pressure from hemodialysis. If the vein fails to reach the proper size which is usually 6 mm or greater then more procedures needed to help the fistula to achieve its proper size otherwise “to mature”.