That is the simple answer, but it is not an actuate answer.
I'm with Bob. Time is indeed a factor to consider. Path through the body is another. Whether or not it is AC or DC also comes into play and I am sure there are other factors as well.
For instance, I have been hung up on a spark plug wire on a dirt bike. The ignition system ran around 10 thousand volts and I was above the let go threshold. Since this happened as a result of me pulling the plug wire off my bike that was running full speed in neutral as a result of a stuck throttle, I only had to endure the shock for a few seconds. I can tell you with no uncertainty that having to endure that same shock for several minutes would have been fatal.
In hospitals, there is a possibility of IV's becoming energized. It only takes a fraction of the current through an IV to be fatal as would a skin contact. That's why there is so much concern about available fault current in hospitals.
A person's health also affects the amount of current that would cause a fatality.
I have been hit by high output automotive ignition systems, around 30 kV. I have also been hit with 277 from a lighting circuit. Trust me, I'll take the current limited 30k over the 277 any day. A high voltage automotive system will deliver a shock like being grabbed and shook by the biggest girl in a country bar. Getting nailed with 277 is like getting kicked by her horse.