Which is why domestic RCD's are set to 30mA (thirty thousandths of an amp for the benefit of those who don't understand the term "milli"). Even 30MA directly across the heart can kill in the right circumstances.
I initially studied electronics at college, so was familiar with currents in the milliamp range. When I joined BT's predecessor Post Office Telephones, they put me on the power section, where I was put to work maintaining DC power systems rated in thousands of amps. Scared the living daylights out of me at first. Then they merged the AC & DC sides and I had to learn to work on 11,000 volt high voltage AC systems, which initially scared me even more!