Well, it does depend on some things a bit. The detectable DC current flowing through our bods is 5 milliamps. Our bods have quite a low internal resistance so if it was an internal connection we could detect a few volts. But our skin has quite high resistance. As much as half a million ohms when dry but as low as a thousand ohms when wet. So to get a current to flow we have two skin contact "resistors" plus our internal resistance (which depends on the path length through the bod.)
My personal empirical experience says I can detect around 60 volts DC but, depending on my skin at the time, it could be a lot higher or a lot lower than that.