This is a silly question. It's your body man... if you can't tell where your own veins are, you have no business doing IV drugs.
There are many veins in that area.. there are also arteries, nerves, etc. That is why we register before injecting.
I'm closing this because no matter what anyone tells you, the only way you're going to know if you're in a vein is to register and be able to inject without any pain.