For me to do such a desperate blood-leaching at home, was mainly to ease my mind.
I had cut myself during cooking a couple of times the last weeks and noticed my blood was DARK DARK RED (more than usual) and very coagulated/thick. And at the time I had high BP and a history of blood-clots. So all in all I was worried about too high hematocrite-levels and possibility of getting blood-clots again (although some people may question the link between hematocrite-levels and blood-clots).
So, I did it a couple of times, getting no more than 2-5ml/session.
Later I got my appointment with the GP. And again, the UK-doctors are cheap ass idiots. He refused to sign me up for a regular blood-panel testing. But at least he measured my BP and it was normal. So at least that easned me a bit. Now, if it was due to the blood-leaching I dunno for sure.
Just make sure u work aseptic. If you got a wound or something, rather play with that under controlled circumstances (i.e. how big u wanna cut it open), rather than playing with ur veins directly (unless u actually dont got medical training to be palying around with syringes and veins).