You can draw lots of blood from a syringe. Find the veins and tie a rubber to your hand to make the veins visible.
Venous blood is rather dark and already has carbon dioxide attached to the red blood cells. Putting that on SN doesn't really show much of a color change at all. It's best to use blood that comes from capillaries (I'd stay away from arteries or arterioles because of the greater chance of infection). People have used diabetic lancets which may work but IMO I don't think you can get enough blood out. However, some people can so that's ok.
I think people overlook the importance of proper hygiene before digging into their skin with things that carry bacteria... Including the skin. This is why I feel that before sticking yourself with a dirty knife, pen or what have you, into your "dirty" bacterial infested skin, use a sterile object (like a new lancet, packaged sterile needle, etc) and sterilize your skin with isopropyl alcohol wipes. When you penetrate your skin with unsterile things, and into a blood vessel, bacteria can invade the tissue (skin, muscle, fat) and possibly cause serious issues. Just something to think about.
