How long after vasectomy until completely sterile?

After a vasectomy, it typically takes about 8 to 12 weeks for a man to become completely sterile. During this time, residual sperm may still be present in the reproductive tract, so it's important to use alternative contraception until a follow-up semen analysis confirms the absence of sperm. Most doctors recommend checking a sperm count about 12 weeks post-surgery to ensure sterility.