If you start nodding off, you had better do something to keep you awake. It is best to have someone with you. If you take a very large dose you may not get the needle out of your arm, but if you take less, most people pass out, go into a coma and then stop breathing.
If you are feeling awake you shouldn't have to worry, just don't do anymore if you are.
It really does not matter how it is taken unless you eat them since it takes longer to feel the effect.
Be careful and enjoy!