Generally the only people that die from a black widow bite are people who are highly allergic to the venom. Just like with people who are allergic to bee stings. If you have been bitten it wouldn't be a bad idea to go to Immediate Care or Urgent Care though, especially if you don't know if you are allergic.
A black widow bite rarely kills human beings but may make you feel sick and that's why it is advisable to seek medical attention immediately. The victim is normally given calcium gluconate or antivenin to neutralize the venom.