For what length of time do i have to get a tetanus shot after i stab myself with a knife?

Depends: If you completed the primary series in childhood & have had one within five years you can probably just wash out a simple wound & not worry.If you have never had the series & have a dirty wound u could see the tetanus begin to set up over a day or so, so a shot & anti-toxin might be needed within hours.If u fall in the middle, get it done within 48hrs, but do a good job of cleaning the wound 1st.